Reprinted from THE WINE REVIEW, June and July, 1937
Heat may also affect the fruit in What climate does an adverse manner. Certain vane- ties are susceptible to sunburn in The relation of weather to the even the normal seasons, and most composition of grapes and wine varieties are burned to a small or large extent in the very hot years. The presence of sunburn has a By A. J. Winkler and M. A. Amerine harmful influence on the flavor of University of California, Davis the must and furthermore, if the amount of raisined fruit is sufficient, LIMATE is usually ranked Direct effects of Climate water may have to be added to along with variety and soil as The influence of heat on the reduce the sugar content of the must C one of the important factors grape's composition is very impor- so that a complete fermentation may controlling the composition of tant. Under the influence of the heat take place. For dry wines this grapes. The climatic belts to which received during the growing season would reduce the percentage of total the grapes are adapted are known the vine manufactures carbohy- acid present and have a doubly de- to lie within the temperate zones; drates and other organic substances leterious effect. especially, in-so-far as the growing which are stored in the fruit and The known direct effects of heat of grapes for wine-making purposes elsewhere in the plant. As the ripen- on the fruit are largely confined to is concerned. It is also recognized ing season progresses the sugar sugar and acid. But the poor quality that within the temperate zone there content of the fruit increases and its generally attributed to our fruit is a considerable difference in the acid content gradually decreases. grown under too hot a condition, or composition of the grapes grown in This direct effect of heat on the in a very warm season, indicates the cool northern limits as compared plant is largely beneficial. If the that other substances are also af- with those grown under warm semiL temperature conditions are cool, the fected by heat to a recognized but tropic conditions. unknown extent. Thus in the Northern European sugar will increase more slowly and the acid decrease less; while, if the The direct effect of rainfall on the countries and to a certain extent in plant may be quite great in unirri- the eastern United States, in certain climatic conditions are warm, the years there is not sufficient heat to sugar reaches higher levels and the gated vineyards in connection with bring the grapes to their proper acid is reduced. This same differ- a warm season. Lack of spring maturity and grapes with high acid ence may occur between a cool and rainfall and very hot early summer and low sugar are produced. Under warm season as well as between a weather may cause a shortage of California conditions and those of cool and warm region, if the differ- water, under which the grape does the Mediterranean region heat is ence between seasons is large not ripen and low-sugar, high-acid not usually the limiting factor and enough. conditions occur in the fruit. in most years the grapes will attain Quittancon states that this condi- Indirect effects of Climate a sugar content great enough to give tion of high sugar is a rare one even the wine at least the proper degree in a district as far south as the The indirect effects of climate are of alcohol. Rhone Valley of France and that also of considerable importance. In The fact that the warmer regions more often there is too little sugar general any influence which climate regularly receive a sufficient supply and too much acid so that sugaring may have on the total amount of of heat during the growing season of the must is necessary. Concern- crop will also affect the composi- does not mean that the difference in ing the vintages of 1908, 1909, and tion of the fruit. In years when climatic conditions from year to 1910 in eastern United States. Al- frost reduces the crop the fruit year will have no effect on the com- wood says that 1908 was of very usually ripens very well, and attains position of the grapes and wines. high quality while 1909 was poor a high degree of sugar. Similar The early and late seasons are a and 1910 not very good. The tem- uniformity of ripening might be ex- reflection of the existence of some perature data for these three years pected if wind or hail reduced the difference in heat conditions from indicate that one of the factors crop. Wine from St. Emilion of 1911 year to year, and even in the warm which caused this difference in qual- is very rare because the crop was portions of the temperate zone fluc- ity was the difference in heat-1908 almost entirely destroyed by hail, according to Shand, but the quality tuations in climate occur which do being the hottest of the three years was fairly good. affect the composition of the grapes, and 1909 the coolest. and therefore of the wines. Caldwell in a more recent study The climate may affect the grape for a five-year period finds that in in a number of different ways. In New Jersey the amount of sunshine general, the amount of heat, wind, received is the dominating climatic and rain may all vary from year to factor affecting the composition of year, and may be received in differ- the grapes and that with high sun- ent amounts during the same period shine there is associated in the grape of a year. Each of these variables high sugar and low acid which for may effect the composition of the the grapes grown in New Jersey is a grape directly or indirectly. relationship indicating high quality. Under extreme drought condi- tions, such as indicated above, lack of rainfall may cause a failure of proper ripening. In the cooler por- tions of the temperate zone where summer rains occur, lack of rainfall during the summer is almost always of some benefit in-so-far as it re- duces the injury of pests and or- ganisms. The season of 1921 was a great vintage in Europe not only be- cause it was a warm year, but also because it was one of the dryest recorded. In the cool, damp vintage seasons there is considerable loss of grapes due to rotting, and if the spoiled fruits get into the must, they not only directly add harmful flavors but also make the fermentation less clean. In the warmer portions of the temperate zone it is not the cool damp seasons which permits organ- isms to develop on the fruit and thus injure the quality of the wine, but it is the very hot seasons which are difficult. The growth of harmful or- ganisms in musts at high tempera- tures is well known and the compo- ; sition of wines made under these conditions is almost always less de- sirable than that of wines made under cool conditions. Even in the cooler parts of the temperate zone the very hot period at the height of the vintage season may have ill effects, as for example, according to Healy the 1895 and 1923 seasons in Bordeaux resulted in poor wine due to excessive heat dur- ing fermentation. Finally, the heat, in that it reduces the acid and in a more or less general way reduces the pH, will allow the musts to be more susceptible to spoilage organ- isms. Also, it may be noted that where an excessive crop is produced due to some sequence of climatic condi- tions, such as a frost one year fol- lowed by a normal season, there is a i marked reduction in the rate of ripening of the fruit, and on many vines the grapes do not reach matur- ity and at picking time have a low sugar and high acid content. Cer- tain varieties such as Folle branche, are also more prone to overcrop than others. The climatic conditions under which grapes are grown may thus affect the composition of the grapes produced not only through direct effects, such as excessive heat, but also indirectly through variation in the crop or due to the influence of weather on the control of pests and organisms. Reprinted from the June, 1938 issue of WINE REVIEW 3,1u2. upri. 4 Climatk diggionA,
ITHIN the geographic zones Is Important in Determining Quality of where the grapes of the W world are grown, wide dif- Wine Types Produced in These Locations ferences in the environmental con- ditions occur between regions. The more marked and best understood By A. J. WINKLER* of these differences is that of tem- Division of Viticulture, University of California perature. Differences in soil types, humidity, etc., also occur but they appear to be of less importance. sary environmental-variety inter- It has been the combination of Also, since the latter factors are relationship for the basis of a wine such specific environments with much less variable in California type. The significance of variety the qualities of the Riesling or the than abroad, we shall confine this in these comparisons is the indica- Pinot noir, or the Cabernet sau- discussion to differences in tem- tion of the great importance of the vignon, etc., that has made possible perature. adaptation of the variety to the the really great wines of the world. For instance, on the Rhine in particular environment in which it On the contrary, if the varieties Germany the seasonal summation it grown. The fact that the va- are without special character, the of heat above 50° F. is only 1700 riety or varieties grown in each of most favorable climatic conditions day degrees while at Jerez in Spain these regions attains almost per- will not make it possible to produce it is 5400 day degrees, or over fect development in that environ- quality wines. The wines of these three times as much. Between ment has made it possible for the varieties will be improved owing to these more or less extremes, as far wines produced to establish a repu- a better balance of the sugar and as viticultural regions go, there are tation for their quality that is acid, etc., of the grapes at matur- intermediate conditions, such as world-wide. ity, but they will still be lacking Chablis with 2000 day degrees, Furthermore, the experiences in the special qualities, such as Burgundy with 2400 day degrees, and researches of the European aroma, bouquet, freshness, etc., Chianti with 3500 day degrees, etc. vintners and enologists afford us a which are characteristic of the Now, long before the methods of fairly definite indication of what quality wines of commerce. obtaining the records from which climate does to grapes. Its effect Under warmer climatic condi- I took the above figures were per- is largely an influence on the rates tions the aromatic qualities of the fected, the vintners of each of the of change in the constituents dur- grapes lose some of their delicacy regions I have named as well as ing development and the composi- and richness and the other con- other intermediate regions had de- tion of the grapes at maturity. stituents of the fruit are not so veloped very definite and distinct Relatively cool conditions in which well balanced, hence the dry wines wine types. Even the relatively these changes, especially those of —even of the best varieties—can- small differences in environment ripening, proceed at a slow rate not compare in quality with those between some of the intermediate have been found to be the most of the cooler regions. While in the regions were, nevertheless, found favorable for the production of dry very hot regions where the growth to be sufficiently distinct so that wines of quality. These conditions and ripening changes of the grapes through the centuries of wine pro- foster the retention of a high de- proceed with great rapidity, the duction definite types have become gree of acidity (see Table 1) and aroma of most dry wine varieties established within their borders. bring the aroma and flavoring con is harsh and coarse and the other At present, the varieties grown stituents of the grapes to their components are so poorly balanced in each of the regions I have named highest degree of perfection in the that usually only ordinary dry are different, hence those of you mature fruit. wines can be made. Yet condi- who have ' had only a limited ex- perience in wine making might be TABLE 1. The Influence of Regional Conditions on the Acid inclined to attribute the principal Content of the Grapes difference in the wine types of these regions to the varieties that Varieties and per cent acidity as tartaric acid are grown rather than to the en- Region Zinfandel Petite Sirah Burger vironment. Yet, if environment in the broad sense of zones limits Bonny Doon (cool) .88 .93 .90 Santa Rosa .67 .74 .69 grape growing generally on the surface of the earth, it should St. Helena .58 .66 .49 Lodi .57 .60 .42 equally as definitely in a more re- Fresno (warm) .44 .51 stricted application limit the adap- .41 tation of the individual variety to Read at the State-Wide Dry Wine Confer- tions of abundance of heat in some regions, thus furnishing the neces- ence at St. Helena, April 30, 1938. regions, which make them poorly I suited to the production of dry possibilities of our state for the the warm to hot margin, as in the wines, fits them ideally for the pro- production of a variety of wine San Jaquin Valley, the conditions duction of fortified wines, such as types. Naturally, these similarities favor the development of a high Port, Muscatel, Sherry, etc. Un- in temperature of our regions with sugar-acid ratio, a low total acidity, der conditions of abundant heat the those of Europe must not be taken and a low tannin content, which varieties which have proven them- too literally. Many factors, such makes it possible to produce high selves to be especially suited to the as variety, differences in soil, hu- quality fortified wines if the proper production of these types of wines midity, length of growing season, varieties are grown. attain their most perfect develop- method of vinification, etc., must The reverse is true under the ment. Large summations of heat, be taken into account before defi- cool to cold conditions of the North especially just prior to and during nite types and qualities of wines Coast. Here the sugar is usually ripening, favor a high ratio of can be established in our regions. relatively low, the acid relatively sugar to acid in the fruit ; and the That we might profit from the ex- high, and the tannin supply is effect of the heat on the aroma is periences of the old-world findings more generous, which makes it pos- not as objectionable as in the case regarding the relation of environ- sible to produce really fine dry of dry wine. ment to type, however, was well wines of the good varieties in the These observations on the influ- exemplified by the superior forti- best locations. It is obvious to all ence of environment clearly show fied wines of the Fresno area and of you who have had experience that a change in these conditions the superior dry wines of the with wines that the differences in changes the character of the fruit North Coast area just prior to the climatic conditions of these of all varieties. In regions of dis- 1918. The leading individual pro- two—our warmest and our coolest tinctly different climates the char- ducers of that era were growing —regions are so great that it is im- acter of the fruit is so changed varieties that were suitable for the possible to produce quality wines that it is no longer suitable for the types of wine they produced and of the same type in both. production of the same type of that were likewise, in most cases, Between these extremes we have wine. Thus, when accompanied by well adapted to the particular en- intermediate regions in which the the proper methods of vinification vironment. Those of you who were environmental differences are less and aging, the regional conditions, acquainted with the wine of that marked. Even here the warmer through their influence on the time and those of us who have had areas are better adapted for sweet sugar-acid ratio, total acidity, the the privilege of tasting well pre- than for dry wines, while the re- tannin content, etc., determine the served wines must agree that the verse is true of the cooler regions. type of wine to be produced; while trend of development in the indus- In the intermediate regions the the variety, through its inherent try was sound. variations in seasonal conditions characteristics, such as aroma, On the basis of climatic condi- will influence the composition of flavoring constituents, freshness, tions, experience under similar the fruit quite considerably, so etc., determines the quality of the conditions abroad, and experience that in warm years it may be bet- wine within the type. in California, it is evident that we ter fitted for fortified wines and in To realize these influences of en- have conditions which in the warm cool seasons for dry wines. This vironment and of variety will re- to hot margin of our grape belt are influence of seasons is not suffi- quire a degree of perfection in the ideally adapted to the production ciently marked in the extremely utilization of regional conditions of fortified wines and which in the warm or cool regions to change the and varieties which can be attained cool to cold margin are adapted to character of the fruit materially. only through years of experimen- the production of dry wines. In Now, if the above is true—and it tation and wine production. Yet this basic interrelationship of type TABLE II. with region and quality with va- Seasonal Summations of Temperature Above 50 F. as riety is fundamental not only to Degree Days for Several Well-Known Regions the progress of our industry as a whole but also to the rational de- Degree Degree velopment of each section of our In Europe days In California days state. The Rhine at Geisenheim... 1700 The reference to region made SSlopes, and valleys opening above was of necessity directed to onto the ocean the conditions as they exist in the { Guadelupe 1950 wine-producing areas of the old The Chablis region—at Au- Lick Observatory 2070 world where the industry is en- rerre, Yonne-Chablis 2000 Aptos 2100 dowed with long years of experi- San Luis Obispo 2150 ence. But what about the condi- tions as they exist in California? Oakville 2300 Climatological records indicate that The Burgundy region at Boulder Creek 2400 we have almost as wide a spread Beaune 2400 Los Gatos 2600 in climatic conditions as occurs in St. Helena 2900 the entire continent of Europe. This is illustrated by Table II. Cloverdale 3300 These figures, comparing the The Chianti region, several Lodi 3600 seasonal summation of tempera- stations in Tuscany 3500 Davis 3600 ture of several California locations Fontana 3700 with wine producing regions of The Sherry region, at Seville 5400 Fresno 4700 Europe, give an indication of the t Bakersfield 5000 is—then the present trend in our est areas, on the other hand, yields dustry this diversity of conditions industry, namely, the attempt of are low, and only quality wines to complicates the problem of types, most wineries regardless of their be sold at high prices will pay the but as time goes on it will, if util- climatic surroundings to produce costs. A natural consequence of everything from Angelica to Ries- the production of the types in each ized appropriately, lend additional ling, indicates that many of you region for which the environment individuality to the small localities are still not acquainted with, or is best adapted would be the re- in this region. A present indica- that you are not willing to be moval of or reduction in competi- tion of specialization within a re- guided by, the relation of environ- tion between regions. Each region ment to type in your operations. has its own special advantages, gion is illustrated by the produc- The economics of the industry, no which, if properly used, will tion of California sauternes in the doubt, has forced some of you, strengthen the position of the in- Livermore Valley. against your better judgment, into dustry everywhere ; and instead of It is only within limited areas this unsound practice of produc- competing, each region will be a where the environmental condi- ing everything everywhere, while supplement and a help to the others of you have been misled by others. tions are approximately the same salesmen who have insisted that Again, if the interregional move- that we can hope to develop fixed you must have all types under your ment of grapes could be stopped, types. The importance of this be- labels if you are to remain in busi- the North Coast region would al- comes apparent if we recognize a ness. most immediately regain its differ- type of wine as being the product Aside from the economic con- ential as a quality dry wine pro- of a given variety (or varieties) siderations, some of the arguments ducing area. The same would be grown on similar soils within a supporting the unsoundness of this true of the best fortified wine trend are: 1. It prevents the estab- areas. The extent of the differ- limited climatic zone and made ac- lishment of a reputation for a ential would, of course, depend on cording to definite methods. To given region, since the production the skill with which the vintners further this quest for ideal locali- of all or many types in any one utilized their environment, varie- ties for the good varieties and to region must of necessity result in ties, and methods. Favorable nat- hasten the day when we may have the production of only average ural conditions are important, but quality or of a preponderance of they alone will not enable any re- definite types, the vintners should ordinary wines. 2. It prevents our gion to attain a reputation. Qual- keep the wines of these varieties regions from becoming known for ity alone will do that. which they make of grapes from a single type as has been the case If you want your wine to sell for different areas within the region in the old-world, and which is the basis for their recognition. 3. It 25 cents, 50 cents, or $1.00 a gal- separate until they have developed lon more than that of another re- to the point of showing their qual- throws all regions in conflict with gion, you will have to put that each other since under this scheme much more quality into your bot- ity. Such a procedure is also the of things all regions are producing sole means at your disposal to ob- the same types. 4. It forces the tles. You have the conditions in movement of grapes from one re- the North Coast for the production tain the highest quality wines pos- gion to another since it is only of quality dry wines, but the only sible from the various lots of way for you to convince the buy- grapes and it is only by such meth- through such movement that ing public of the superiority of the grapes of an approximately suit- wines of your region is to grow the ods that you will discover the va- able composition for all the types right varieties in the proper en- riety (or varieties)-environmental can be had in a single location. vironment, pick them at the proper combination for a distinctive type The movement of grapes be- stage of maturity, and convert of wine for each part of the North tween regions constitutes the greatest abuse of our natural con- them, without dilution of their Coast region. ditions and is responsible for many quality by mixing, into really fine As soon as the North Coast has of the difficulties of the industry. wines. And of as great importance again found itself as a producer of To stop it would encourage each as stopping the practice of dilution dry wines, especially when appro- region in the production of the types for which their conditions with poorer grapes, you must pre- priate variety-environmental com- are suited. In the warmer regions vent your really fine grapes from binations for the basis of types the types would be fortified or finding their way into the wines of have been discovered, and when common dry wines, while the cooler other regions, where they would the vintners are willing to cast regions should produce standard tend to elevate the quality and their lot entirely with light wines, and superior dry wines. The eco- thereby reduce your differential. nomics of grape production in the it should be a simple matter to ob- several regions as well as the en- In a region so large and varied in tain regulations that will check the vironmental conditions underlie topography as the North Coast, present indiscriminate movement this distribution of types. marked variation in the exposure, of grapes into and out of your re- In the warmer regions where the slope, and soil type occur to form gion. Naturally, as long as your soils are rich, the yield high, and many small areas, hence the quest where the quality of the fruit even wineries produce all types, such of the best varieties is only ordi- for the proper environmental con- regulations can serve no purpose. nary, common wines of common ditions for the fine varieties must Likewise, until you have something but productive varieties may be be carried on within the region. In distinctive of your region you have produced with profit. In the cool- the present state of flux of the in- no basis for asking for protection. DEGREE-DAY CALCULATION
To calculate "degree-days", use the following method
First, determine the average temperature , for the day: (High Temperature + Low Temperature) 2
Then, subtract 50°F. from the average temperature: (High Temperature + Low Temperature) - 50°F 2
The result of this calculation is expresses as "degree-days" Here is an example: (90 + 50) 21 (average temperature) 2 70 - 50 = 20 degree-days for that day
HEAT SUMMATION CALCULATION
Heat summation is an extension of degree-day calculations. In heat summation for viticulture, the individual degree-day values for each day from April 1st through October 31st are added together. The full-season heat summation values in wOrld viticultural regions typically range between 1700 and 4500 degree-days.
VITICULTURE "REGIONS" For characterizing viticultural regions according to seasonal heat summation, five categories have been established:
REGION I up to 2500 degree-days REGION II 2501 to 3000 degree-days REGION III 3001 to 3500 degree-days REGION IV 3501 to 4000 degree-days REGION V over 4000 degree-days
S. KREBS, 1/96 Zug Some Limitations of the Degree Day System as Used in Viticulture in California G. N. MC INTYRE', W. M. KLIEWER2. , and L. A. LIDER 3
The average and range in dates of budbreak, bloom, and fruit maturity of five grape cultivars grown in five differ- ent climatic regions of California were determined over a period of two to six years. For each cultivar and climatic region, a comparison of the variation in the average number of degree days and duration (in days) for three de- velopmental periods (budbreak to bloom, bloom to fruit maturity (20°Brix), and budbreak to fruit maturity) was made. No statistically significant difference was observed between the two procedures. Determining the number of degree days by digitizing the area under the thermograph curves for five different locations gave de- gree day values for the period 1 April to 31 October that ranged 6% to 22% lower than the traditional method of mathematically averaging the maximum and minimum temperature per day. For a given cultivar, there were wide differences in the number of degree days required for the developmental periods between the five locations. Possible reasons for these differences are discussed.
The degree day concept has enjoyed widespread ac- early January to mid-February of each year that data ceptance among viticulturists (3,4,6,16,17,19,20,21) as were collected. Vines were balance-pruned according to well as those studying other crops (7,8,10,11,15) for over vine capacity and in all cases were judged to have 200 years (1,12,14); however, the procedure as currently adequate leaf area to mature the crop without a delay in used in California and elsewhere has many weaknesses sugar accumulation, i.e., were not overcropped. In this (1,2,5,9,13,14,18). Degree days are the positive remain- communication, budbreak is defined as the day when a ders when a plant-specific base temperature (commonly leaf is first visually separated from a bud on approximat- 10°C or 50°F) is subtracted from daily average tempera- ley 10% of the primary buds per vine; bloom is the day tures. Accumulations of degree days are thought to pro- when 50% of the primary flower clusters have at least 5% vide a general indication of thermal conditions in a cap fall (calyptras had come off flower parts), and fruit particular viticultural region. The accumulation is as- maturity is defined as the day when extracted berry juice sumed to approximate the same total at specified stages reaches 20°Brix. The study sites at Davis, Parlier, and of vine development, regardless of whether the season is Soledad, California, were irrigated according to accepted cool or warm. Indeed, when temperature is the main commercial practices for these areas, but those at Ho- climatic factor limiting vine development, degree day pland and Oakville, California, were not irrigated. Sea- accumulations may be a useful indicator of season length. sonal rainfall in the latter two sites usually averages However, if temperature conditions are adequate, other between 800 and 1000 mm, two to four times that of the factors such as solar radiation, day length, or soil mois- former three sites. ture may be more important limiting factors and are likely reasons for observed variations in accumulated degree day totals. Such situations exist in California, and Conclusions . this paper demonstrates wide variation in degree day Three major limitations in the accuracy of the degree totals observed during the growing season in five distinct- day heat accumulation system, as used by viticulturists, ly different vine-growing regions of the state. have been demonstrated in this paper. First, the initial Materials and Methods accumulation is often substantially in error due to the non-symmetrical way that heat accumulates diurnally in The experiment was so designed that five cultivars of many areas of California, which is not taken into consi& Vitis vinifera were replicated in five locations with five eration by summing up the daily mean temperature above vines per replicate using the same clone of each cultivar 10°C. Second, degree day accumulations between bud- in all locations (Table 1). Phenological observations break, bloom, and fruit maturity (20°Bris) were just as (dates of budbreak, bloom, and maturity) were made of variable as simply using the number of days between the five randomly chosen vines, representing each cultivar at various phenological stages averaged over a period of each site. The period of observation of these vines varied several years. Finally, individual cultivars showed a wide between two and six years, between 1968 and 1973. The range of responses in different locations, undoubtedly due five widely separated locations were selected because of to the influence of other climatic variables and genotype their known differences in climate and viticultural char- acteristics. All Carignane vines were cordon-trained and differences. These; findings suggest that the use of the spur-pruned, while the other four cultivars were degree day system is most suited to areas ,in which daily all head- temperature increases and decreases follow a symmetrical trained and cane-pruned. All plots were pruned between diurnal pattern:;The need for including other . factors, 'Lecturer in Geography, University of Newcastle, N.S.W., Australia; and 2,,Professor of such as solar radiation, day length, daily temperature Viticulture, Department of Viticulture and Enology, University of California, Davis, CA 95616- 5270. ranges, soil moisture, etc. for more accurately describing To whom all correspondence should be addressed. climatic regions is greatly needed. The authors are grateful to Norm Ferrari for assistance in collection of phenological data. This research conducted at The University of California, Davis, and the University of Newcastle, N.S.W., Australia. -- Manuscript submitted for publication 25 July 1986. Copyright © 1987 by the American Society for Fnology and Viticulture. All rights reserved.
111:4. PiPkNIAC■c,101■18;N9. 2; 1987 America Europe World
Geisenheim 1709 Trier 1730 Rheingau 1745
REGION I Salinas 2144 Connawar ra 2175 2500- Oakville 2300 Sonoma 2360 Beaune 2400 Hawkes Bay 2470 World Geographical Distribution of Viticulture San Luis Ob. 2555 Bordeaux 2519 Santa Rosa 2610
Douro 2765 REGION II 2501-3000 10 °C, 50 ° F Sta. Barbara 2830 Barossa 2838 St. Helena 2900 Asti 2980 20 °C. 68 °F
Seymour 3050 Equator
Livermore 3260 Clare 3231 REGION III 20 °C, 68 °F 3001-3500 Calistoga 3360
Adelaide 3458 10 ° C. 50 °F
Note that virtually all qualify wine is produced in the regions situated in the temperate-zones betweer Florence 3530 Great Western 3505 the 10 °C and 20 °C lines. (These are the mean temperatures over the whole year.) Pomona 3676 Rutherglen 3654 A U.S.A. Stockton 3715 Benalla 3715 B Chile, Argentina' REGION IV Sacramento 3788 C Portugal, Spain, Italy, France, Germany, Austria, Switzerland, Czechoslovakia 3501.4000 D Algeria, Greece, Hungary, Rumania, Bulgaria, Yugoslavia, Israel, U.S.S.R. Berri 3840 E South Africa F Australia, New Zealand Sonora 3927
Riverside 4032 Naples 4010 Davis 4057 Swan Valley 4079 San Bernard. 4126 Palermo 4140 REGION V Griffith 4170 4001+ Jerez Front. 4194
Pokolbin 4538 Fresno 4680 Algiers 5200 SONOMA NAPA
• Cloverdale
1 s.. SONOMA • GOYSer111.0. , CrSo I 2 /4- 4-#0 4 • s•-•,4 4 • $,•Healdiburg aoy , - - 4 \•Windsor ogs Fl` • Guernevnia 4a .• Forestville • St Helena 4% • Santa Rosa Sebastopol• Kenwood• • Rutherford Glen Ellen. os • Oakville • 5 • YountvIlle te, .
• Petaluma 5a
1. Alexander Valley 1. Napa Valley 2. Dry Creek Valley 2. Howell Mountain 3. Knights Valley 3. Carneros 4. Russian River Valley 4a. Chalk Hill 4b. Sonoma-Green Valley 5. Sonoma Valley 5a. Carneros
---C • •
Al A MI- DA, SANTA CLARA, SAN] A CRUZ MENDOCINO AND LAKE
• Berkeley • Emeryville • Oakland
San Leandro 1 • Livermore Pleasanton • MENDOCINO ALAMEDA
Mission San Jose
Mountain View • Sunnyvale • San Jose o> Saratoga SANTA CLARA CI, 2 • Navarro "•-, 'LAKE I --•,` Los Gatos • 2%40 U k I ach • 4°*0 Lakeport Boulder Morgan Hill -4-e, Creek . Philo. '6•=3, • • 4 SANTA CR UZ San Martin. Boonville• Py ae Hopland • Felton• • Scotts Valley Kelseyville • Soquel • Gilroy
Santa Cruz 5 Middletown.
1. Livermore Valley 1. Potter Valley 2. Santa Cruz Mountains 2. Anderson Valley 3. McDowell Valley 4. Clear Lake 5. Guenoc Valley
SAN LUIS OBISPO AND SANTA BARBARA MONTEREY AND SAN BENITO
Shandon . San Juan Bautista Paso Robles • , • < Santa Barbara 1. Paso Robles 1. Caul-lel Valley 2. Edna Valley 2. Chalone 3. Santa Maria Valley 3. Arroyo Seco 4. Santa Ynez Valley 4. La Cienega 5. Paicines SOUTH! RN CALIFORNIA SAN JOAQUIN VALLEY SIERRA FOOTHILLS SAN BERNARDINO Lodi SAN JOAQUIN antecaj • . • Escalon Ripon • San Bernardino • Modesto • Ontario STANISLAUS • Riverside Merced MERCED RIVERSIDE 1 • Temecula • Cutler 1 KINGS • Escondido 2 SAN DIEGO Bakersfield • • San Diego 1. Temecula 1. El Dorado 2. San Pasqua! Valley 2. California-Shenandoah Valley . VINE PROTECTION Bruce Bearden Farm Advisor-Mendocino County Lov. Temperature Effects In parts of California both spring and fall low temperature injury are common. Temperatures that cause winter kill of fully dormant vines, 10 ° F. or - 12° C., rarely occur in grape growing regions of California. Spring frost which injure developing shoots and reduce the current seasons crop are the most often considered type of low temperature damage. Cold injury to green growth begins at air temperatures of 31° F for a duration of hour, the air temperature being measured by a sheltered minimum thermometer four feet above the ground. Air temperatures of 26-28 ° for a duration of several hours will kill all act- ively growing green parts of the vine including buds that have begun to open. There are often degrees of damage; shoot tips . may be killed but clusters . may remain intact, shoots may be killed back including the cluster, but leaving several viable basal buds on the damaged shoot or the shoots may be killed back entirely. Depending on the degree of frost damage strategies for stripping dam- aged shoots from the vine have been developed. Spring and fall cold injury to the trunks of young vines may be severe. Dam- age usually occurs during the first fall or spring following training up the stake. Damage is mainly confined to the live bark and may range from very obvious to quite subtle. In the more obvious cases spring shoot growth quickly becomes stunted or very irregular. Longitudinal cracks appear in the bark, and in many cases aerial grown gall infection takes place in the bark cracks. Vines injured by spring or fall low temperatures will often sucker profusely at the crown which becomes an important indicator of trunk damage. Occasionally fall frost occur before harvest. Such early frosts are often relatively light and may only present a problem with the harvest at hand. All leaves usually drop from frosted vines within a few days and within ten days the berries begin to shatter from the clusters. What Causes Cold Damage It is generally considered that cold damage is caused by the rupturing or injury to plant cells or cell membranes when their contents freeze and expand. The contents of the cell expand by 8-9% when freezing occurs while other plant tissues tend to contract as they get colder. , Following freezing, the damaged cells can no longer control their liquid contents and dehydration takes - place. The formation of ice crystals in tissue is by no means consistant being dependant on several factors besides the air temperature and its duration. Under certain conditions actively growing grape tissue can be super-cooled to temperatures below freezing without the formation of ice crystals and without subsequent damage. The amount of stored carbohydrate in the tissue plays a part in retarding ice formation and is often referred to as "anti-freeze". It has also been recently understood that ice crystals implant tissue re- quire nuclei, and the presence or absence of substances which act as nuclei in- fluences the point at which ice crystalization takes place. The discovery that certain bacteria provide a nucleus for ice crystal formation has led to one en- tirely new approach to frost protection through the elimination of the bacteria. Variations In Cold Damage Cold damage in the vineyard is often quite irregular, varying from vine to vine and among shoots on the same vine. The most commonly considered variable factor in vine susceptability to low temperature damage is lack of carbohydrate reserve, sometimes called lack of maturity. Vines growing on gravelly or sandy soils may suffer from water stress and be unable to store carbohydrates. Vines in wet spots may have impaired root systems and often do not mature either their fruit or their wood. Excessively vigorous vines which continue to grow actively in the fall may fail to store carbohydrates in favor of making new growth. Cabernet sauvignon is well known as a vigorous variety which starts growth late in the spring and tends to grow late in the fall. Establishment of Cabernet on fertile soils in districts where early November frosts occur can be quite difficult. Spring "T" budding has resulted in fall cold damage due to delayed vine maturation. Fall low temperature injury sometimes goes unrecognized on estab- lished vines. Dead and dehydrated spurs which fail to grow in the spring may be the first symptom of trouble that is noted. At pruning injured wood is lighter green in cross section and appears dry but these symptoms are easily overlooked. Vineyard Frost Protection For many California grape growers the question of whether to go into frost protection or not is difficult. In some districts and favored locations within districts frost losses are infrequent. In the North Coast spring frosts are generally frequent enough and winegrapes valuable enough to have made frost pro- tection almost universal. With the -development of overhead sprinkling for frost protection, grape pro- duction has been expanded into areas that could not otherwise be considered for grape production. The need for frost protection ranges from little or none to absolutely essential. The projection of a cost benefit ratio for a frost protection system must include variables such as the probablility of future frosts and their severity, the future price and availability of fuels and energy and the price of wine grapes. Given these kinds of variables it is difficult to make a cost benefit projection with confidence. -2- As the need for frost protection varies so do the methods, which include relatively simple cultual practices, furrow and limited sprinkler irrigation, wind machines, sometimes augmented by diesel burning heaters and continuous over- vine sprinkling. Cultural Practices Spring radiation frosts can be modified by 1-2 degrees by improving the daytime heat absorbing potential of the vineyard soil. This amounts to storing more of the heat radiated by the sun during the daytime for release at night. A clean, firm and moist soil absorbs and radiates heat best. Early spring cul- tivation followed by rain or irrigation produces the desired surface. Cold air is heavy and tends to flow like water and trees bordering a vine- yard may act as cold air dams. Air movement of only 3-4 miles per hour mixes the warmer air above the vineyard with the colder air close to the ground. The re- moval or thinning of border trees helps promote air movement and usually reduces the frost hazard. Double pruning can delay bud break on selected buds for a week. The success of this procedure depends on the fact that buds at the tip of a cane will be- gin growth first while those at the base of the cain are retarded. On spur pruned vines the vine is pruned normally except that instead of two bud spurs a cane of 6-10 buds is left. After the tip buds on the cane begin growth and before they are inch long the vines are repruned back to the desired two or three basal buds which have not yet begun to grow. Following spring frost damage the selective removal of certain damaged shoots has proven beneficial. Those shoots which have been killed back just far enough to kill. the developing clusters but with one or two viable buds remaining at their base are removed. This is because these buds will begin to grow and are rarely if ever fruitful. If these basal portions of the damaged shoots are broken out, secondary dormant buds will grow and produce some fruit. After trunk damage to young vines the process of retraining should be delayed until vigorous regrowth indicates where the damage is. It is best to retrain young vines with healthy new shoots than to encourage and wait for the healing of damaged tissue. Frost Protection Methods Permanent set overhead sprinklers have emerged as the method of choice for difficult conditions. These systems derive their effectiveness from the heat of fusion, which is given up as water turns to ice. As long as there is a mixture of ice and water on the vines the temperature of the ice-water mixture and the tissue below it will remain at 32 ° F. just one critical degree above the point where vine damage begins. Overhead sprinkler systems are designed to apply .11 inches of water per hour, which requires 55 gallons per minute per acre. At this rate full protect- ion of vineyards to temperatures in the mid-twenties has been achieved. Overhead sprinkler systems are expensive and require a substantial water supply. They do not require extensive labor to operate, they are clean and quiet in operation, do not use large amounts of fossil fuels and can be used for irrigation, pest and disease control, heat suppression, vineyard establish- ment and spring and fall frost protection. -3- 2c3 Wind machines depend on mixing warm air from above the vineyard with the colder air at ground level for effectiveness. A wind machine alone can raise the temperature in the vineyard by 25% of the difference between the air temp- erature at 4' and 40'. If there is a difference of four degrees you can get a 1 0 temperature rise. If there is little difference between the temperature in the vineyard and above, wind machines are ineffective unless used with heaters. Ten HP per acre is recommended for effective frost control. Orchard heaters are almost always used in conjunction with wind machines, rarely alone, in vineyard frost protection. A common density is ten per acre and most growers perfer to place the heaters around the border of the vineyard. Modern orchard heaters will meet air pollution standards in California when properly operated. While even spacing of heaters throughout a vineyard is more efficient than border placement, one man on a tractor with a flame thrower can light a row of heaters in a vew minutes eliminating the need for a labor crew in the middle of the night. Heaters burn up to a gallon of diesel oil per hour. Current and future cost and availability of oil makes continued use of heaters questionable. One completely new approach to frost protection is under investigation by Dr. Steven Lindow at UCB. He is working on the theory that certain bacteria are responsible for initiating the formation of ice crystals in plant tissue. With- out a plentiful supply of these bacteria, ice formation occurs at temperatures several degrees lower than when they are present. Field experiments for two years have been hampered by lack of spring frosts. Laboratory evaluations using a cold chamber indicate that there is in fact a difference between tissue treated with a bacteriacide and untreated tissue in response to cold temperatures. Recording The Temperature All fr:ost protection work in the field is based on air temperatures re- corded by a sheltered thermometer four feet from the ground. This standard- ization is necessary because thermomether exposed in different ways record different temperatures. A thermometer directly exposed to the sky will record a temperature lower than one shielded from the sky and one located closer to the ground will reflect the colder temperatures at ground level. Good instrumentation allows good management of a frost protection system while poor instrumentation may lead to unnecessary expenditures of energy and money. Growers in areas where cold temperature injury are likely to occur could profit by the operation of a recording thermograph. This instrument traces a continuous temperature line on a seven day chart and records extreme temperatures as well as durations. -4- THE CHRONOLOGICAL CLASSIFICATION OF GRAPEVINE PHENOLOGY G. N. McIntyre, L. A. Lider and N. L. Ferrari Respectively, Lecturer in Geography, University of Newcastle, New South Wales, Australia 2308; Professor of Viticulture and Research Associate, Department of Viticulture and Enology, University of California, Davis, California 95616 Manuscript submitted 9 July 1981. Revised manuscript received 20 November 1981. Accepted for publication 18 December 1981. ABSTRACT This paper addresses the problem of defining and tive to each other, in the onset of budbreak and bloom, using terms like 'early', 'average', and 'late' as they are but maturity is less predictable due to greater vine used when describing phases of grapevine development. management variability. Associations between develop. One hundred fourteen cultivars have been compared ment phases of grapevines and various climatic indica- over seven seasons and listed according to the time each tors are discussed, and the prospect of matching culti- attains budbreak, bloom, and maturity. Most of the vars to climates is raised. vines studied demonstrate a striking consistency, rela- The frequency with which loose terms like 'early' and attained each development stage was determined and 'late' are used to describe grapevine development has led the average yearday for all cultivars then calculated for the authors to explore the possibility of introducing each stage. Using these calculated averages, a hypotheti- precision to this practical convention. In doing so, many cal 'average vine' can be envisioned which buds, blooms, cultivars have been studied over a number of differing and matures on the yeardays coinciding with averages seasons, with the average day (for all cultivars) on which for all 114 cultivars. Each cultivar has been compared specific phenological stages occur being calculated. This with this 'average vine' to determine its relative order in work enabled subsequent comparison of individual cul- each stage of development. tivars with these averages, and the determination of Meteorological data were obtained from a recording 'how early' or 'how late' was a particular cultivar or an station located on the Davis campus less than one individual season. The definition of these features in kilometer from the vineyard. climatic terms is then also possible. Establishment of vine averages: One notable fea- ture emerges from this study; almost all cultivars are MATERIALS AND METHODS observed to bloom a consistent period (within a few During the years 1968 to 1974 phenological observa- days) before or after the 'average vine'. Since the abscis- tions (the dates of budbreak, bloom, and maturity) were sa in Figures 1 to 3 represents seasonal climatic influ- made of three-vine groups of 114 cultivars of Vitis ences, it is reasonable to assume that bloom date in a vinifera grown in the teaching vineyard at the Universi- particular year, for a given cultivar which does not ty of California at Davis. All vines were budded onto conform to this pattern, resulted primarily from vari- rootstock A x R #1 (Ganzin 1) which possibly means ations in management (e.g. pests, irrigation, tractor that self rooted cultivars might develop at different rates damage, time of pruning) or from the many difficulties even though the test vines were the subjects of normal inherent in vine observation. Exceptional weather at the management procedures. Table grape cultivars were time of bloom may also explain part of this variation for cordon trained and spur pruned, while wine grape late blooming cultivars. A 'best-fit' line (see Fig. 2) for a cultivars were head trained and spur pruned. Pruning specific cultivar, drawn parallel to the 'average' line for was during dormancy, but unfortunately its timing could all seasons studied, minimizes these errors and enables not be fully controlled. The soil is uniform throughout the standardization of bloom time, relative to the aver- the vineyard, being a very fertile, deep, fine-sandy-loam, age and to other cultivars. and it was irrigated during the study period. The consistency of these standardized data is quite The stages were arbitrarily defined as follows; bud- high; the average standard deviation for all differences break for a specific cultivar was defined as they day between corrected and actual yeardays at bloom being when leaves could first be recognized on 10% of the 1.7 days. This standardization of phenological observa- primary buds, bloom was the day when 50% of the tions ensures that meaningful comparisons can be made primary flower clusters had at least 5% of the calyptras with climatic data, since the major errors in the pheno- off, and maturity was regarded as the time when 20° logy data due to non-climatic factors have been re- Brix was attained in the extracted juice. The yearday moved. (number of days after January 1) on which each cultivar The association between actual and corrected year- 80 Am. J. Enol. Vitic., Vol. 33, No. 2, 1982 GRAPEVINE PHENOLOGY — 81 e: r.1 0 °Z. en 0) 01 out■yoUrAWANIEWAM111121111,411MI MI C•CONCoRD P11/4111PASSINIPAU/AMINFAMIIIIIMINIA10111/ 6 C G (s.1.4) I0 - 13MIONWIRIIIMIMMILIM1011■ BEAUJOLAIS ■ ■ ■■■ ■ ■1111. G GtflAy NIL 0111• ∎ . • • (5 • 14) IFIRIA WAWA IrAIVAIS r A ALMERIA (6.1.9) A AultRIA AVALMIAVAWimriwAINNI AY2266 0,0.0 DAY R CE. ■ R061 CABERNET NI 7=MM= (5 • 1.0) AVERAGE 1 1 111111111. •011MBN2211W C CRASSELAS DORE D Ay ■ ■ ■ 12,T10411FAMMFArlyeArAlWi& Is BLACK ROSE 11 61 1M1111WM (5.2.2) (5. s) V- 1 -1 5 Affiarir *--R RUBY CABERNET '401/2111" cs.2'8) 10 15 to 1 5 50 MAY I0 DATES OF BLOOM (AVERAGE vio.) Fig. 2. The timing of bloom for five sample cultivars. 2 16 21 26 31 40 MARCH DATES OF 601■ 6REAK (AVERAGE VINE) PAr C CONCORD Fig. 1. The timing of budbreak for three sample cultivars. One Mr ipro 8.0 standard deviation on either side of the mean for each cultivar is indicated by shading. 26 days is not so close for budbrea,k, where pruning date ARLY E V" ilevAl differences from year to year (especially late pruning) YS YS A introduce considerable variability. Nevertheless, a best- D fit line (see Fig. 1) still enables reliable standardization to be made of the date of budbreak for a single cultivar relative to the others. Here the average standard devi- ation for all differences is 2.4 days. Figures 1 and 2 AVEIAGE II present comparisons between a selection of cultivars and DAY the average for all cultivars studied. 12• Rub), cADEMJET liMilia (S•7-0) The relative position of all the cultivars at maturity is much more irregular than for the first two develop- I IMO ment stages. A number of factors cause variability in the onset of maturity to increase substantially. Aside from I I accidents in normal vineyard practice, pests, disease, 3 and variable yield may all cause sugar levels to rise at IrrAllign A • ALICANTE BOUsCHET inconsistent rates. For this stage, differences between (S. G'3) actual and corrected data produce a standard deviation of 8.9 days, and consequently standardization of data is Er Ali Ai less reliable for maturity. Examples of this point are seen in Figure 3. On the basis of these associations, all the cultivars IA 28 7 ITT under study have been arranged in their standardized AUGUST SEPTET-IRAK order of budbreak, bloom, and maturity (see Tables 1 to DATES OF MATURITY 3) rounded to the nearest whole day. These tables are, (AVERA4E vewa) therefore, timetables for the three development stages at Fig. 3. The timing of maturity for three sample cultivars. Am. J. Enol. Vitic., Vol. 33, No. 2, 1982 q, 82 — GRAPEVINE PHENOLOGY Table 1. The relative onset of budbreak. Days Cultivars – 11 Beauty Seedless, Pearl of Csaba –10 Perlette, Loose Perlette, Early Muscat – 9 July Muscat – 8 – 7 Chenin blanc, Malaga – 6 Sultana, Mantuo Pilas – 5 Delight, Almeria – 4 Tokay, Rish-Baba, Suavis, Black Prince – 3 Pinot blanc, Barbera, Gray Riesling, Chardonnay, Gamay Beaujolais, GewUrztraminer, Concord, Emerald Riesling, Niabel, Monukka – 2 Grenache, Orange Muscat, Alicante Bouschet, Cardinal, Pinot noir, Gros Colman, Calmeria, Italia, Salvador, Canner, Muscat Hamburg (T) – 1 Alicante Ganzin, Tinta Cao, Aligote, 17-11, Aramon, Black Corinth, Thompson Seedless, Ribier, Olivette blanche, Gold, Muscat blanc, Feher Szagos Average Semillon, Cornichon, Refosco, Petite Bouschet, Alvarelhao, Sylvaner, Chasselas dory, French Colombard, Tinta Madeira, Flora, Pierce, Scarlet, Emperor + 1 Grignolino, Muscat Hamburg(W), Royalty, Charbono, Touriga, Red Malaga, Folle blanche, Early Burgundy, Trousseau, Aleatico, Barlinka, Kandahar, Green Hungarian + 2 Tannat, Red Veltliner, Palomino, Dismar, Verdeiho, Golden Muscat, Sauvignon blanc, White Riesling, Gamay + 3 Zinfandel, Helena, Burger + 4 Furmint, Sauvignon vert, Black Rose, Dattier, Pinot St. George, Peverella, Petite Sirah, Kishmishi, Mission + 5 Muscat of Alexandria, Carignane, Grand noir + 6 Ruby Cabernet, Calzin, Grillo, Black Malvoisie + 7 Malbec + 8 Merlot, Cabernet Sauvignon, Valdepenas + 9 Malvasia bianca +10 Inzolia +13 Mataro, Souzao +15 St. Emilion the Davis vineyard. They may be expected to apply, with in maturity date. Perlette is a heavy bearing cultivar an accuracy indicated by the standard deviations men- which requires rigorous crop regulation, but since this tioned above, whether the season is long and cool or was not carried out sufficiently here, the vine is seen to short and hot. mature two weeks or so later than would be the case The position each cultivar occupies in Table 3 must under commercial conditions. Conversely, experience be viewed with some caution. In addition to the high has shown Almeria to be a cultivar of low pollen fertility standard deviation involved, cultural practices can have which is naturally light cropping but which is considered a substantial effect. For example, Muscat Hamburg has a very late maturing variety when normally cropped. It been cultivated as both a table grape where it was is seen to mature here possibly two weeks earlier than cordon trained and some crop thinning was used (indi- usual. Those cultivars marked (?) are placed in this table cated by T) and a wine grape (W) variety where it was on the basis of only one or two year's data and may be head trained with no thinning. The effect of the two substantially in error. No data at all were available for management systems is seen in a three week difference cultivars missing from Table 3 (e.g. Black Prince). Table 2. The relative onset of bloom. Days Cultivars – 11 Pierce –10 Concord – 9 Niabel, Pearl of Csaba – 8 Chardonnay – 7 Pinot noir – 6 Pinot blanc, Gamay Beaujolais, Early Muscat – 5 Golden Muscat, Beauty Seedless – 4 Perlette, Sylvaner, Rubired, Salvador – 3 Mantuo Pilas, Scarlet, GewUrztraminer, Aligote, French Colombard, Muscat Hamburg(T), July Muscat, Loose Perlette – 2 Touriga, Tinta Cao, Verdeiho, Black Corinth, White Riesling, Barbera, Chenin blanc, Suavis, Early Burgundy, Royalty Alicante Ganzin – 1 Petite Bouschet, Alicante Bouschet, Helena, Alvarelhao, Rish-Baba, Pinot St. George, Folle blanche, Gray Riesling, Chasselas dore, Muscat blanc, Muscat Hamburg(W) Average Semilion, Oranige Muscat, Feher Szagos, Charbono, Malbec, Merlot, Delight, Ribier, Tokay, Cardinal, Malaga, Almeria, Refosco, Ita- lia, Tinta Madeira, Aleatico + 1 Green Hungarian, Zinfandel, Palomino, Gamay, Emerald Riesling, Queen, Sauvignon blanc, Gros Coleman, Calmeria, Red Veltliner, Olivette blanche, Burger, Trousseau + 2 Grand noir, Sauvignon vert, Emperor, Cabernet Sauvignon, Gold, 17-11, Grignolino, Aramon, Black Malvoisie, Flora + 3 Mission, Tannat, Grillo, Monukka, Sultana, Canner, Barlinka, Peverella, Muscat of Alexandria, Petite Sirah, Dismar, Ruby Cabernet + 4 lnzolia, Thompson Seedless, Cornichon, Black Prince, Kishmishi, Calzin, Carignane, Dattier, Malvasia bianca, Furmint + 5 Red Malaga, Kandahar, Valdeperias + 6 Black Rose, St. Emilion, Souzao + 7 Mataro Am. J. Enol. Vitic., Vol. 33, No. 2, 1982 GRAPEVINE PHENOLOGY— 83 Table 3. The relative onset of maturity. Days Cultivars –58 Black Corinth(?) – 42 Pearl of Casaba – 37 Sultana –34 Beauty Seedless VERY EARLY – 33 Early Muscat, Loose Perlette – 32 Delight –28 Concord – 25 July Muscat – 24 Cardinal, Dismar(?) –23 Monukka – 22 Scarlet, Verdelho(?) – 20 Golden Muscat –19 Sauvignon blanc(?), Perlette, Gold, Suavis – 18 Muscat Hamburg(T) – 17 Merlot(?) EARLY –16 GewUrztraminer, Kishmishi, Orange Muscat(?), Malvasia bianca(?) – 14 17-11 – 13 Pierce, Sylvaner –12 Chardonnay, Gamay Beaujolais, Muscat blanc – 11 Pinot blanc, Helena(?) –10 Malaga, Kandahar, Tannat(?) – 9 Pinoit noir, – 8 Thompson Seedless – 7 White Riesling, Red Malaga, Grignolino(?), Tinta Cao – 6 Canner, Cabernet Sauvignon, Emerald Riesling(?) – 5 Furmint, Flora, Salvador – 4 Aligote, Red Veltliner(?), Rish-Baba, Muscat of Alexandria – 3 Gray Riesling, Italia, Tinta Madeira, Early Burgundy, Malbec, Souzao – 2 Palomino, Aleatico(?) – 1 Niabel, Sauvignon vert, Trousseau, St. Emilion Average Rubired + 1 Mission MID SEASON + 2 Semillon, Chenin blanc, Alvarelhao + 3 Peverella, Grenache(?) + 4 Pinot St. George(?), Royalty + 5 Ruby Cabernet, Dattier, Muscat Hamburg(W), Touriga + 7 Queen, Calmeria(?), Valdepeflas(?) + 8 Alicante Ganzin + 9 Petite Sirah, Gamay, lnzolia +10 Ribier, Carignane, Mataro +11 Calzin +12 French Colombard, Cornichon +13 Grand noir +14 Zinfandel, Mantuo Pilas . ...... +15 Emperor, Petite Bouschet +16 Chasselas don§ +19 Tokay +20 Almeria LATE +21 Black Malvoisie +22 Charbono +23 Grillo +24 Black Rose, Alicante Bouschet +28 Gros Colman +29 Olivette blanche +31 Folle blanche +37 Green Hungarian VERY LATE +40 Feher Szagos +43 Refosco +48 Aramon +50 Burger Clearly this timetable for the date of maturity could tion of these sequential lists, it follows that a few be improved if vine management were more closely cultivars, selected from various parts of each list, may controlled. This is a most difficult task, but it will provide a useful indication of the course of vine develop- probably be attempted in due course. With the prepara- ment for all the others, most notably the more commer- Am. J. Enol. Vitic., Vol. 33, No. 2, 1982 84 - GRAPEVINE PHENOLOGY cially important ones. (3) suggests that summations of daily maximum air It must be stressed at this point that these findings temperature differentiate between periods of high and may only relate to vines grown under the conditions low energy inputs to an evaporating surface better than applying at the Davis vineyard. Fortunately, the ab- do those of the means, and the same may be said for a stract 'average vine' for Davis is approximated by the developing leaf canopy. Between budbreak and bloom, cultivar Semillon. Elsewhere, however, this may not be cane growth and the rate of dry matter production is the case, and different conditions could possibly rear- high, and limiting maximum air temperatures are un- range the order of these lists or vary the number of days common in Davis at this time of year. Consequently only over which they extend. Indeed, the lists may well the lower portion of the normally accepted curvilinear provide a 'yardstick' for measuring the impact of aspect, association between the rate of photosynthetic produc- slope, latitude, soils, and climate in other vineyard tion and air temperature (7) is relevant and the warmer locations. This point is being studied further. the day the better. Climatic considerations: Tables 1 to 3 suggest an Cumulative global radiation is not a good indicator of order of three phenological events for the cultivars the time between budbreak and bloom, a period during under study; what is now required is an indicator for the which leaf area is constantly increasing, but it provides timing of these events. Since meteorological data have the best indicator of the time between budbreak and daily cycles but vine development stages eventuate after maturity. It is an excellent measure of the energy load many weeks, such an indicator should either represent sustained by vines over an extended period, having a `triggering' levels of specific meteorological variables or direct influence on soil and air temperature (4), tran- incorporate their daily accumulation. The latter course spiration rates (7), and photosynthesis (5). A close is the most widely adopted (6,7) and is pursued here. association has been established between accumulations of net radiation and surface temperatures over extended To be useful, a cumulative indicator must produce a periods by Budyko (1) and Table 4 indicates that a consistent total, year after year, regardless of season, similar association probably exists between global radi- and regardless of the number of days between develop- ation and air temperature at Davis. Cumulative air ment stages. A useful measure of any indicator's consis- temperature is, therefore, a useful substitute when radi- tency is the Coefficient of Variation (CV), which is the ation data are not available, in locations where other percentage ratio of the standard deviation and the mean, conditions resemble those at Davis. and has a value of zero for an ideal indicator, where there Cumulative daily air temperature difference (maxi- is no annual variation. Table 4 gives a number of mum minus minimum) is the most reliable indicator for indicators for the timing of the average vine at Davis the time between bloom and maturity. This is an inter- between three development stages and their related esting indicator suggested by Kriedemann (Personal standard deviations converted to equivalent days, and communication, 1980). For the daily value to be high, CVs, for six of the seven years under study. The first maximum temperature must be high, and Table 4 shows season was not part of the CV calculation as this was the first year the vines bore fruit, and their development was this to be a useful measure. However, if minimum temperature is also high, the value will be reduced, as it irregular. The timing of budbreak was not part of this will if maximum temperature is low. It seems to success- study. fully incorporate a number of different environmental The average number of days between each stage of circumstances. development is shown in Row 1, and the CV for this Like most plants, grapevines respond to the integrat- simple measure is a base-line indicator upon which any ed effect of a number of environmental variables, any other measure must improve to be more useful. Higher one of which may restrict development by deviating CVs than these are naturally not acceptable. Degree- from optimum conditions for the vine. In this study, the days represent a slight modification of mean daily air authors have established the most relevant single cli- temperature, and as such, this measure is the subject of matic variables for three phases of grapevine develop- much criticism (2). It provides a marginally better ment in what is virtually a field laboratory, where as indicator for the first development stage (budbreak to many variables as possible have been held constant. It is bloom), but is no improvement for the other two. quite likely that a better environmental indicator can be Cumulative maximum temperature is the best indi- derived for the vines at Davis (and elsewhere) from an cator for the first phase (with a CV of 3.8). Fitzpatrick integration of several variables, each contributing var- Table 4. Various climatic indicators of development stages for the average vine. CV is the Coefficient of Variation and SDD is the Standard Devi St. Dev. x No. of Days). SDD implies that in two years out of three each system will produce the mean indica- ation expressed in equivalent Days ( mean for shown within this number of days either side of the day the particular development stage is reached. System Budbreak to Bloom Bloom to Maturity Budbreak to Maturity Mean SDD CV Mean SDD CV Mean SDD CV Number of Days 54 4.5 8.4 113 3.0 2.7 167 5.3 3.2 Degree Days °C 287 4.4 8.2 1442 4.3 3.8 1729 6.7 4.0 Cumulative Maximum Temperature 1289 2.1 3.8 3732 2.8 2.5 5021 3.0 1.8 Cumulative Radiation (langleys) 33368 3.3 6.1 77871 2.5 2.2 111239 2.7 1.6 Cumulative Temperature Difference 886 4.0 7.4 2302 2.0 1.8 3188 4.7 2.8 Am. J. Enol. Vitic., Vol. 33, No. 2, 1982 GRAPEVINE PHENOLOGY — 85 iously. This possibility is currently being investigated. for vineyards where climate may be limiting. Once the climate of an otherwise suitable site has been assessed CONCLUSION and the number of days within the growing season Grapevine development rates may be influenced by available for vine development determined, the most climatic variability, management practices, vine pathol- appropriate cultivar may then be selected to fit the ogy problems, or grafting differences, and because they available length of season. It is even possible to intro- often interrelate, isolating the impact of any one of these duce probabilities of success for a range of cultivars if factors is very difficult. The authors have examined the the probability of return cycles for specified season problem of isolating the influence of climatic factors. It lengths is calculated. has been demonstrated that individual grape cultivars tend to develop at consistent rates relative to others, LITERATURE CITED regardless of seasonal conditions, and at each stage of 1. Budyko, M. I. The Heat Balance of the Earth's Surface, development are located in regular positions within the (Translated by N. Stepanova, 1958). Leningrad (1956). whole population of cultivars studied. Since broad sea- 2. Chang, Jen-Hu, Climate and Agriculture: An Ecological Sur- sonal climatic variation causes the whole population to vey. Aldine Publishing Company (1968). be earlier or later than usual any cultivar substantially 3. Fitzpatrick, E. A., Estimates of pan evaporation from mean out of order has most likely been influenced by non- maximum temperature and vapour pressure. J. Appl. Meteorol. 7 climatic factors. A reference point has been suggested (1963). here, the timing of which has been related to a number 4. Geiger, R., The Climate Near the Ground, Harvard University Press, (1971). of climatic factors. 5. Kriedemann, P. E., E. Tortikfalvy, and R. E. Smart, 'Natural It might be expected that tighter control of non- Occurrence of Sunflecks by Grapevine Leaves', Photosynthetica, 7 climatic factors than was possible for this study would (1972). increase precision, and the climatic requirements of 6. Weaver, R. J., Grape Growing, Wiley-Interscience, 1971. individual cultivars could be reliably determined. The 7. Winkler, A. J., J. A. Cook, W. M. Kliewer and L. A. Lider, system may then be useful in helping to select varieties General Viticulture, University of California Press (1974). Am. J. Enol. Vitic., Vol. 33, No. 2, 1982 Z66 C.7 • ■ c . . ‘ 'jd LVV:i %} e• -.... . ',-a• - is\ LJ i j....‘-J•,.‘:,,,,• \ . \ <77_1 (\1 ,3 "--7.\1 ‘ re ••■_.2....t , "'',.r. . .. i I.-.1) '...-'.,:...' \ ! I h.,. i t I %-,, l J,..f.:.1 I Q CZ2.) j:;)..1..1 J..4.\J --,' 1:0171-1--!..,...... . ..1.....'1. . r . )\ \ r-ri II -,....1_,TY_.. CTIO (1-7017\ 1 . ( ,.... TA-11.'r: /1 :'•\ ./ ' Z.. APRIL 1975 Contents ,.,,, , I • '''... , ...:-' -^.- i, I FROST PROTECTION - ) )2/ PRESS FROST HAZARD vs GROUND PREPARATION EXTRA SPRINKLER FROST PROTECTION DEW POINT TEMPERATURE FROST HAZARD vs GROUND PREPARATION Strive to have moist, firm bare ground surfaces prior to frosts. Accomplish this by immediately following your discing operation with a light irrigation to re-settle and • firm the soil, or by mowing your covercrop very closely to the ground. If you can, irrigate in the mornings before a frost so the sun can warm the soil up during the day. Data on ground preparation versus sheltered thermometer readings (at 4 feet height) indicate the following: * Bare, firm, moist ground warmest * Shredded covercrop, moist ground . 1/2°F colder * A low growing covercrop even though the ground is moist 1 to 3° colder * Dry, firm ground 2°F colder * Freshly disced, fluffy ground 2°F colder * High covercrop 2 to 4 ° F colder but in some instances where the high covercrop restricts air drainage 6 to 8 ° F colder SPRINKLER FROST PROTECTION] -' • A minimum precipitation rate of 0.11 acre inch per hr. equal to 50 gallons per minute per acre has afforded adequate (6 to 8°F) frost protection provided: The sprinklers were turned on soon enough and --- The sprinklers were run continuously until after sunup and temperatures were Above 32° to 36°F. The operating pressure and sprinkler design afforded good coverage and over- lap of water. Turn Sprinklers on Soon Enouch A drop in temperature is expected when sprinklers are first turned on --- Usual California FROST conditions involve rather'high dew points. Under these CO.orwati v. Extension work ins Agriculture ond Home Ecarlernks.Uniled States Deportment of Agriculture and Unive•t:ty 01 Cali'ornia co-operating cond,tions only a slight drop in temperature is expected until the sprinklers have made see•al revolutions and wetted the vines. Consequently, starting sprinklers before temperatures drop below 33 to 34°F usually provide adequate protection. Unusual FREEZE conditions such as experienced during the spring of 1972 involved very low dew points and corresponding low humidities. A significant drop in temperature was experienced when sprinklers were first turned on. In some cases damage occurred. Pay attention to the dew point! Frost vs Freeze Protection Freeze conditions imply low dew points and low humidities and wind velocities above 3 mph. Dew point versus the temperature at which you turn on your sprinklers can make the difference between adequate protection--or damage. THE LOWER THE DEW POINT, THE HIGHER THE TEMPERATURE AT WHICH YOU NEED TO START YOUR SPRINKLERS. The table below shows the relationship of dew point and starting temperatures for turning on sprinklers. DEW POINTS STARTING TEMPERATURE TEMPERATURE OF SPRINKLERS 26°F and above 34°F 24 - 25°F 35°F .22 - 23°F 36°F 20 - 21°F 37°F 17 - 19°F 38°F - 16°F 39°F Run The Sprinklers Long Enough For the usual radiation FROST condition with high dew points and calm weather it is safe to end sprinkling when the sun is up and the air temperature outside the treated area has climbed to 32°. For the unusual FREEZE condition with low dew points and breezy weather it is wise to wait until the air temperature has risen to 36°F. Damage was reported in 1972 when turnoff at 34° left considerable ice on the vine and the temperature dipped back to 32°F during an early morning breeze. Running the sprinklers until after sunup and turnoff when the temperature reached 36°F would be safe even though all the ice on the vines had not melted. ' Pay Attention to the Dew Point Low dew point temperatures indicate when to turn on the sprinklers as well as how long to run them. Table 1 on the next page tells how to figure the dew point temperature from wet and dry bulb thermometer temperatures. e ; • Sincerely, • " ' LC ( Rudy A.'Neja Farm Advisor 118 Wilgart Way Salinas, CA 93901 Phone: (408) 758-4E37 I. The University of California's Agricultural Extension programs are available to all, without regard to race, color, or national origin.