PES Their Characteristics and Suitability for Production in Washington EB 635 January 1972 Cooperative Extension Service College of Agriculture Washington State University Pullman Contents

Kinds of 3 The American-type 3 The European-type grape 4 Hybrids-French and American 5 General response to environment 5 Winter injury 5 Influence of length of growing season on selection of grapes 6 Heat units during the growing season 6 Influence of soils on grape production 7 Precipitation, diseases, and soil moisture 7 Selecting grape varieties and locations 8 Summary 12

Tables 1. California grape classification system 7 2. Desirability of soils for various types of grapes 7 3. Relationship between length of growing season and performance of grapes 8 4. Accumulated heat units at various locations in south central Washington 10 5. Grouping of grapes by vigor and maturity 11 6. Classification of potential sites for grape production in central Washington 11

Figures 1. Mean length of growing season, mean number of frost-free days 9 2. Mean number of days over 28 degrees 9 3. Approximate relationship between heat units and number of frost-free days 10

2 Grapes-Their Characteristics and Suitability for Production in Washington

By Ronald B. Tukey and Walter J. Clore*

There is renewed interest in producing grapes wilds which are now referred to as the "American­ in the state of Washington. Although grapes type" grape. Most have a strong "foxy" flavor have been grown in commercial quantities for a and aroma, a tender flesh, and "slip skin." Con­ hundred years, problems in developing markets cord is the best known and most widely cultivated have always limited expansion of the industry. variety of this type. Until recently, only small quantities of grapes Crosses have been made between the more have been used for . About 90 per cent of hardy, wild American grapes and the European the total crop has been of the variety Concord, vinifera. These have resulted in the so-called produced for the grape juice market. hybrids (American and French) grown primarily The development of new irrigable lands in in the northeast United States and southeast Can­ central Washington has focused attention on ada. grapes as an alternate high-value crop. New meth­ European varieties introduced into Mexico and ods of trellising grapes have increased yields while California found a warm, dry climate which fa­ the introduction of mechanical harvesting has of­ vored their growth. They are the base upon which fered distinct advantages for managers of large the large California fresh table grape, raisin, and acreages. wine industries have developed. Some are grown At the same time, there has been a sudden in­ in the very warm interior valleys while others are crease in the demand for grapes for wine. In­ better adapted to the cooler valleys along the volved are premium type table as well as coast. new wines utilizing large quantities of Concord While there are still other types of grapes, it and other American-type grapes. The lack of is the American, European, and hybrid which are additional land in California and ­ of primary interest in Washington. suitable for large acreages has at­ tracted the wine industry to Washington. This publication outlines some of the major The American-Type Grape differences between the various types of grapes The American-type of grape is known for its used for juice and wine and to indicate how each slip skin, soft flesh, and distinctly musty or "foxy" is adapted to conditions in Washington. flavor and aroma. Developed in the Northeast, it is characteristically hardy and resistant to a large Kinds of Grapes number of diseases and insect pests. Varieties are moderately vigorous, highly productive, and ma­ Grapes are one of the oldest and most widely ture early in the season. distributed fruit crops in the temperate zone. For There are about 300,000 tons of American­ thousands of years, they have been used as a type grapes produced in the United States. New source of fresh fruit, dried into raisins, or pressed York is the leading state, producing about half into juice for wine. Early Europeans who came of the total. Washington is second with 55,000 to America as traders, missionaries, and settlers to 60,000 tons. It is followed by Pennsylvania brought with them varieties prized in their own and Michigan. About 80 to 90 per cent of this native countries. Here they found other types of production is of the variety Concord. grapes used by the Indians. The variety, Concord, as well as most other Attempts to grow the high quality European American-type varieties, is not well adapted to vinifera-type grapes in the eastern part of America met little success. Cold and disease were the major problems. Instead, the early pioneers de­ * Extension Horticulturist, Washington State University, Pull­ man, and Research Horticulturist, Washington State University veloped new varieties from grapes found in the Irrigated Agriculture Research and Extension Center, Prosser.

3 growing conditions in California. In contrast, produce various kinds of wines. New varieties production per acre in Washington is almost twice were developed for the warm interior valleys and as high as in any other state in the nation. for other kinds of markets. As a result, there are The principal market for the American-type rna jor differences between the European grape grape has been the large centers of population industry and those associated with California al­ in the Northeast. It is marketed in three ways. though both are based upon the same general type JUICE AND JELLY MARKET. This is the (species) of grape. largest market for American-type grapes. It de­ GENERAL CHARACTERISTICS OF EUROPEAN­ pends almost exclusively upon the variety Con­ TYPE GRAPES. The differences between the Eu­ cord. In recent years, per capita consumption of ropean-type grape varieties and the American types Concord juice and jelly has been declining. Com­ involve not only the fruit but also the vine and petition from eastern production has limited ex­ its adaptation. Characteristically, the berries are pansion in Washington. firm-fleshed, nonslip-skin and relatively mild fla­ WINE MARKET. The use of American-type vored. Most varieties require comparatively warm grape varieties for wine is primarily a develop­ weather and a long growing season to mature. ment of in the eastern part of the United The vines are vigorous and produce heavy, upright States. About 20 per cent of the production of growth requiring special trellising and attention grapes in the East is utilized on this market. Pre­ to soils and soil management. They are quite ferred are such varieties as Delaware, , tolerant of heat, drought, sandy soils and soils of and rather than Concord. a relatively high pH. These are some of the char­ Only about 5 per cent of the production in acteristics which make this type of grape more Washington is utilized in this manner. Com­ subject to winter injury, particularly under north­ petition from produced from ern conditions where the growing season is short European-type varieties has limited the develop­ and midwinter temperatures go down to zero and ment of these Eastern-type wines in Washington. below. Recently, a new sparkling burgundy-type Another important difference between the wine, using the variety Concord as a base, has European-type grape and the American relates been developed and marketed as "Cold Duck." to susceptibility to insects and diseases. Downy The acceptance of this sweet wine has startled the mildew and fruit rots limit the development of wine industry and created a new demand for Con­ plantings in the more humid conditions of west­ cord juice. It is this new, relatively unknown ern Washington. A number of different grape market development which has stimulated Con­ viruses are of major concern. They reduce vine cord grape prices and the rapid expansion of the vigor and productivity and increase the suscepti­ industry in Washington. How long bility to winter injury. this market will continue is unknown. Nematodes and the grape are other FRESH MARKET. The sale of American-type concerns. Certain soil-borne nematodes transmit grapes on the fresh market has been limited. Some viruses from infected to healthy plants. The grape grape varieties are used by homemakers for wine phylloxera is a louse which feeds on the roots. as well as juice and jelly. A few are still eaten Both conditions require the use of resistant root­ as fresh grapes. Campbell Early has been the stocks. chief variety used in Washington for this type of Fortunately, phylloxera has not been a prob­ market. Its potential has not been fully explored, lem in Washington. While nematodes are pres­ but it is undoubtedly limited in comparison to ent, plantings have been remarkably free of major other uses of the American-type grapes. viruses. As a result, European grapes can be prop· agated from cuttings and grown on their own roots in Washington. In California, special root­ The European-Type stocks are required. (Vinzfera) Grape WINE MARKET. While small in comparison to the raisin and fresh grape markets, the market When the European grape was brought to for wine is expanding. European varieties are the California, it underwent tremendous change and principal source of sparkling, dessert, and table redevelopment. Varieties associated with specific wines. The first two types of wine represent the grape-growing regions of Europe were utilized to largest market. Varieties used for this purpose

4 are best adapted to the hot, dry, and long growing hybrids has been in the cooler growing regions season found in the interior valleys of California. such as New York, Ohio, Pennsylvania, and New The market for table wines has been small, England. In these areas, they have served as sub­ but during the last decade it has increased dra­ stitutes for the European-type grapes which are matically. The grapes used for these wines are not sufficiently hardy to be grown. specific varieties best adapted to cooler areas such as the small valleys along the coast of California. In these cool areas, varieties develop the type of General Responses to quality required for premium . Environment To meet the needs of this expanding table wine market, additional acreage is required. The The adaptation of grapes to various growing cooler regions in California are limited, and the areas or regions is closely associated with the re­ varieties required are better adapted to central lationship of the different kinds of grapes and Washington than to the warm interior valleys of varieties to several factors: 1 ) winter in jury; 2) California or the severe winters experienced in the length of the growing season; 3) summer tem­ eastern grape regions of the United States. peratures; 4) soils; and 5) rainfall, precipita­ tion, and irrigation. Several of these factors are interrelated, yet they can be outlined separately. Hybrids-French and American See the following sections. The term "hybrid" as used here does not rep­ resent the botanical or scientific cross-species. Many so-called American and European grape va­ Winter Injury rieties are technically hybrids, yet are more charac­ There are several degrees of winter InJury teristic of one type or the other. Therefore, they found in grapes. The most frequent type is the are not included in this section. killing of the primary fruiting shoot in the bud. Hybrid grapes of commerce represent varieties At the same time, there may be some killing of which are intermediate between the American the less mature tips of canes. Either may be the and European grape. They are characteristically result of low winter temperatures or a sudden more resistant to cold, the grape phylloxera, and drop in temperature during the winter. The loss powdery mildew and are associated with fewer of even a high percentage, 2 5 to 50 per cent kill problems with major virus diseases. of the primary buds, can still result in a full crop. GENERAL CHARACTERISTICS OF HYBRIDS. This can be accomplished by retaining the more As noted, the hybrid (French hybrids and Ameri­ hardy secondary buds to supplement the loss of can hybrids) represents an intermediate-type primary buds. grape. The plants are more vigorous than the A more serious type of cold injury is that American varieties and most require a warmer which damages the main arms and trunk of the and a longer growing season to mature the crop vine. Injury can ·result from extremely low win­ and develop resistance to early fall and winter ter temperatures or untimely cold during the fall cold. The type of growth, foliage, and fruit is before the vines have become fully mature. Such more characteristic of the European grape varie­ cold injury may weaken or devitalize the vine or ties. While they retain some of the strong flavor actually kill the above-ground portion of the vine. and aroma of the American grapes, they are usual­ Recovery from either is slow and may require ly firmer fleshed and do not have the characteris­ complete redevelopment of the vine from the tic slip skin of the American varieties. ground up. Probably most important is their resistance to FACTORS THAT INFLUENCE COLD INJURY. cold, their adaptability to areas where the growing While low temperature is a major factor influ­ season is more moderate, and their marketability. encing cold injury, there are others which can be PRINCIPAL MARKETS AND USES. The French equally as important. One is the type and variety hybrids and other hybrids of commerce have two of grape grown. Care should be taken to grow markets, both of which are presently limited but only varieties which mature the crop sufficiently expanding; namely, the wine market and the fresh early to recover properly after . Areas with market (including purchases made for production longer growing seasons can grow varieties which of homemade wine) . The principal use of these mature later.

5 Similarly, overcropping can result in injury. tion of grape varieties. Involved is not only the Fruiting is devitalizing. Vines which have carried maturing of the crop but also the recovery and excess fruit are weakened and are therefore more maturation of the vines after harvest. The rela­ subject to winter injury. tionship may be expressed as follows: Irrigation, soil, and fertilizer practices are im­ Areas with Less than 150 Frost-Free Days: Con­ portant. Practices which delay crop maturity and sider only American-type grapes and the earliest encourage vines to grow late into the fall favor maturing hybrids. more winter injury. Areas with 150 to 160 Frost-Free Days: Most ANTICIPATED RESPONSES TO LOW TEMPERA­ American-type grape varieties and several early TURES. The types of response or in jury which maturing hybrids can be grown. A season of can be anticipated from low temperatures follow. only 160 frost-free days is marginal for all but Zero and Above (F.): Occurring during mid- the earliest maturing European-type grapes. winter, following a period of cool weather, Areas with 160 to 170 Frost-Free Days: Some these temperatures may cause some loss of pri­ early maturing European-type and hybrid grape mary buds or even canes of all grapes that have varieties can be grown under cultural practices grown late into the fall. Little, if any, injury and soil conditions which favor early maturity. and no loss would be anticipated with well­ Areas with 170 to 180 Frost-Free Days: Many matured vines. If these low temperatures fol­ early maturing European-type and hybrid grape lowed a period above 30 to 40° F., they might varieties can be grown. result in some damage to European-type grapes Areas with over 180 Frost-Free Days: This is the as well as to some hybrids. most desirable length of the growing season for Temperatures Down to -10° F. During Midwinter: early maturing European-type and French hy­ These temperatures are likely to cause injury brid grape varieties. to both buds and trunks of European-type grapes and, probably, crop loss. Killing of some primary buds on American-type grapes with in­ Heat Units During jury to trunk and arms may occur with weaker vines. Hybrids should be intermediate between the Growing Season these two, with a significant loss of crop. Where low winter temperatures and the Temperatures Down to -20° F. During Midwinter: length of the growing season are two of the major These temperatures would be expected to se­ factors limiting the survival of grapes, another verely damage or kill most unprotected Euro­ factor is the temperature during the growing sea­ pean grapes and seriously injure hybrid grape son. While grapes will grow at temperatures over trunks and canes. Injury to American-type 32 o F., they require temperatures of over 45 o F. grapes would be less, but, nevertheless, would to grow vigorously and mature large crops with likely result in significant crop reduction. a high sugar content. (Some of the lesser known European varieties Heat during the season is particularly im­ developed for colder regions of Europe and portant in wine grapes. During cool seasons, Asia have shown good survival and production grapes tend to be lower in sugar and higher in following exposure to these low temperatures.) acidity. Warmer weather results in increased Early Freeze in Mid-November: Temperatures sugar with somewhat less acid. This relationship down to + 10° may cause serious injury to is expressed in accumulated heat units, calculated European grapes with crop loss excepting on from monthly mean temperatures over 50° F. the more hardy varieties and well-hardened-off multiplied by the number of days in the month. vines. Such temperatures may cause some loss The total for a season (April-October) depends of buds on American-type grapes with greater not only on high temperatures during the summer in jury and some crop loss on hybrids. but also on the length of the growing season. The desirability of heat units depends upon Influence of Length of Growing the variety of grape and its use. In general, most Season on Selection of Grapes American-type grape varieties are grown under conditions of over 1800 but less than 2 5 00 heat The length of time between bloom in late units. With over 3000 heat units per season, spring and harvest is a major factor in the selec- vine vigor is more difficult to maintain while

6 grape production and quality is lower. The sugar than 24 inches of rooting depth, it should be content can be high, but the acidity is low and the avoided because of low productivity. color is less desirable. In determining rooting depth, take care to Some European-type grape varieties and a identify hardpans, calcareous or caliche layers, or number of hybrids grow well with less than 2 5 00 layering which can cause perched water tables. heat units, but a range of 2500 to 3000 heat units These can be as limiting as basalt or other rock favors higher production, higher sugar, and better layers. American-type grapes are more sensitive quality. With 3500 heat units and <;wer, European to high lime and soils with a pH over 8.0 than are and hybrid grape varieties develop more sugar either European or hybrid grapes. while the acid content is lower. Although less limiting, soil texture and fer­ CALIFORNIA GRAPE REGIONS. Areas where tility can have a major influence on grape per­ grapes have been grown in California have been formance. The American-type grapes are less vig­ classified into five regions according to the ac­ orous and, therefore, require the use of finer tex­ cumulated daily mean temperature above 50° F. tured soils which are higher in fertility. In con­ between April 1 and October 31. The coolest trast, the more vigorous hybrids and even more districts are in Region I where the accumulated vigorous European grape varieties should be degree days are less than 2500. The warmest grown on more coarse, less fertile soils. This per­ district is Region V with over 4000 degree days. mits better control over vine vigor, maturation of This classification system is summarized in Table the crop and wood, and resistance to winter injury. 1. While these represent total heat units, the This relationship is shown in Table 2. manner in which these units are accumulated can have a major effect on quality. These are now f Table 2. Desirability of Soils for Various Types of as well defined as desired. However, excessive Grapes heat during the summer (over 90 to 100 ° F.) is not desirable. Sandy Loams Loamy Sands Type of Medium Medium to Low Sands Grape Fertility Fertility Low Fertility Table 1. California Grape Classification System American Good Acceptable Questionable Grape Degree Hybrids Good Good Acceptable Region Days Weather Suitability for Wine European Acceptable Good Good I Less than 2 500 Cool Best dry table wines. White varieties pre­ ferred. II 2500-3000 Moderately Superior red and Precipitation, Diseases, cool white table wines. and Soil Moisture III 3000-3500 Moderately Good standard red warm and white wines. In areas such as western Washington where IV 3500-4000 Warm Natural sweet wines precipitation and humidity can be high, diseases and standard table can seriously limit grape production. They infect wtnes. leaves, new shoot growth, older wood, and cause V Over 4000 Hot Best dessert wines. fruit rots. As a group, the American-type grape varieties tend to be more resistant. Many of the hybrids have fair resistance, while the European varieties are the most susceptible. Influence of Soils on Grape Fluctuating soil moisture as well as high soil Production moisture during the growing season can present problems. Grapes of all types are very sensitive Soils can be a major factor in the production to poorly drained soils which result in "wet of grapes. Most critical is soil depth and drainage. feet." Fluctuating soil moisture can result in sec­ Grapes have an extensive root system and, there­ ondary growth, delayed blossoming and fruiting, fore, prefer deep, well-drained soils. Consider uneven ripening, and delayed fruit maturity. Even soils which will not permit rooting down to at though fall and winter temperatures may not be least 3 feet as limiting. Unless a site has more severe, irregular soil moisture can make vines

7 subject to late fall and early winter freezes. All of Concord grapes have been grown commercially of these problems tend to be more acute with the in the lower elevations of the Columbia Basin ir­ European-type grape varieties and least serious rigation project and in the Wenatchee-Okanogan with the American-type. River Valleys. All have growing seasons of about 150 days or longer. Few of the hybrid and European-type grapes Selecting Grape Varieties and are well adapted to such a short season. Preferred are areas with at least 160 to 170 frost-free days. Vineyard Locations This relationship is shown in Table 3. As indicated One of the features of Washington is the re­ in Figure 2, areas with more than 150 frost-free markable range of conditions which can be found days are located either west of the Moun­ within the state. Significant differences can be tains or in south central Washington within a found between regions in precipitation, sunlight, radius of 50 miles of Pasco and Kennewick. and temperature. Within regions there are differ­ ACCUMULATED HEAT UNITS. While the ences in soil, elevation, and length of growing sea­ length of the growing season limits the type and son. All have an effect on the selection and per­ variety of grape grown, one of the critical differ­ formance of the different types of grapes. ences between sites is the distribution and accumu­ Identifying areas in the state where grapes lation of heat units. Studies of grape growing might be grown commercially is aided by years of areas around the world have shown that tempera­ experience with American-type grapes, particular­ tures over 50° F. have a significant influence on ly the variety Concord. Being one of the earliest the maturation and quality of the crop. maturing and hardy varieties, it is useful in estab­ There is a general relationship between ac­ lishing the extreme limits of probable production. cumulated heat units and number of frost-free Developing guidelines for the hybrid and Eu­ days, as shown in Figure 3. It shows that areas ropean-type grapes is more difficult. Much of the with less than 155 frost-free days are approxi­ experience with these grape varieties has come mately equal to the cooler coastal areas of Cali­ from limited research and commercial trials in the fornia, Region I, where some of the driest wines Yakima Valley. These trials have shown that a are produced. Areas with between 15 5 and 17 5 number of different varieties can be grown suc­ frost-free days are approximately equivalent to the cessfully. However, more work is needed to de­ most important table wine districts in California, termine which varieties are best suited to different Region II. These areas are considerably warmer slopes, exposures, elevations, and . than the grape growing areas in New York, Penn­ LENGTH OF THE GROWING SEASON. One of sylvania, Ohio, and Michigan. the most useful general guidelines to delineate po­ Areas with over 175 frost-free days resemble tential grape sites is the length of the growing Region III in California. These are areas which season. This is the average number of frost-free may be too warm for the best production of Ameri­ days per year. Such information is available from can-type grapes but are well suited to hybrids and weather records and has been outlined in Figures European-type grapes. However, it is not suffi­ 1 and 2. ciently warm nor is the season sufficiently long Most of the present grape acreage is located to grow the later-maturing varieties. in the lower Yakima Valley. Additional acreages While this general guideline is useful in iden-

Table 3. Relationship Between Length of Growing Season and Performance of Grapes

Length of Growing Season, Performance of Various Type Grapes* Number Frost-Free Days American Hybrid European

Under 140 Marginal Unsuitable Unsuitable 140-150 Good Marginal Unsuitable 150-160 Preferred Fair Marginal 160-170 Preferred Satisfactory Fair 170-180 Good Preferred Good Over 180 Satisfactory Good Preferred

* Performance of selected varieties.

8 Figure 1. Mean length of growing season, mean number of frost-free days ( 32 °).

Figure 2. Mean number of days over 28°F.

9 0 0 II\ 3500

3000

2500

150 160 170 180 190 200 210

NUMBER OF FROST-FREE DAYS-LENGTH OF GROWING SEASON Figure 3. Approximate relationship between heat units and number of frost-free days (length of growing season). tifying general regions of the state where hybrid Some sites may have accumulated 50 per cent more and European-type grapes may be grown, further heat units by early summer than others in the study is needed. The accumulation of heat units, same general area. The effect that these differ­ even within the same geographic area or elevation, ences may have upon the performance of various varies considerably between sites (see Table 4) . varieties is not well known.

Table 4. Accumulated Heat Units at Various Locations in South Central Washington

Total Length of Elevation, Accumulated Heat Units from April Through Each Month* Heat Growing Location Feet April May June July August Sept. Oct. Units Seasont Wenatchee Airport 1229 18 282 810 1566 2251 2698 2751 2751 187 Mattawa 840 48 346 907 1697 2475 3000 3121 3121 180 Priest Rapids Dam 460 138 557 1208 2091 2925 3522 3680 3680 203 Wahluke 416 210 675 1305 2235 3103 3703 3920 3920 195 Hanford (25 mi. NW Richland) 773 102 483 1047 1863 2607 3081 3186 3186 175 Pasco (15 mi. NW) 608 117 619 1139 2074 2734 3196 3199 3199 206 Ice Harbor Dam 368 90 385 943 1730 2480 2987 3170 3170 194 Kennewick 392 132 513 1074 1849 2553 3000 3118 3118 187 Kennewick ( 10 mi. SW) 1500 3 260 722 1451 2124 2568 2630 2630 183 Prosser ( 5 mi. NE) 840 36 270 750 1394 1990 2365 2427 2427 157 Paterson 377 144 569 1229 2001 2763 3315 3411 3411 181 McNary Dam 348 105 455 1037 1850 2625 3117 3265 3265 212 Walla Walla Airport 1170 39 299 776 1533 2237 2714 2853 2853 202

*Accumulated monthly mean temperatures above 50° F. times the number of days per month April 1 through October 31. t Average number of frost-free days.

10 GRAPE VIGOR AND EARLINESS. Grape vari­ CLASSIFICATION OF POTENTIAL SITES. A eties can be grouped according to the vigor of the very general guideline of the potential of various vine and how ear1 y in the fall the crop matures. types of grapes and grape varieties can be made Varieties which are less vigorous as well as those which considers 1) vine vigor, 2) how early in that mature their crop relatively early in the season the fall the crop matures, 3) the length of the are less susceptible to winter in jury and can be growing season, and 4) soil type. Differences grown in areas with a shorter growing season. in soil type, fertility, and length of the growing A general grouping of these varieties is shown season can make certain potential sites more ad­ in Table 5. Particularly noteworthy is the con­ vantageous. Such a grouping has been outlined siderable overlap between groupings for the same in Table 6. type grape-European or hybrid.

Table 5. Grouping of Grapes by Vigor and Maturity

Vigor Vine Group Vigor Grapes

A Medium American Varieties-Early to medium-early: Concord, Campbell Early, Diamond, Dela­ ware, Niagara, Ontario, Buffalo European Varieties-Early: , Meunier, Gewiirtztraminer, Csaba, Miiller-Thru­ gau, Ottonel B Medium high European-Early to medium-early: , , Semillon, White , , Sylvaner Hybrids of American and European Grapes-Early to medium-early: Naples, Seibel 10868, Verdelet (Seibel 9110) c High European-Medium-early to medium-late: Wine types: Carignane, , , , French , Grey Riesling Table types (also used for blending) -Medium-early to medium-late: Cardinal, Black Monukka, Early Muscat, Perlette, Thompson Seedless Hybrids of American and European Grape--Early: Foch, Himrod, Rosette (Seibel 1000), Cascade (Seibel13053)

Table 6. Classification of Potential Sites for Grape Production in Central Washington*

Desirability of Site According to Length of Growing Season, Soil Type, and Fertility Loamy Sands Length of Growing Sandy Loam Medium-Low Sands Group Type of Grape Season (Days) Medium Fertility Fertility Low Fertility

A American Varieties Under 160 Good Questionable Questionable 160-170 Good Acceptable Questionable Over 170 Preferred Good Acceptable B European: Early to medium-early Under 160 Acceptable Acceptable Acceptable Hybrids: American 160-170 Good Good Acceptable and European Over 170 Preferred Preferred Good C European: Medium-early Under 160 Questionable Acceptable Acceptable to medium-late, 160-170 Acceptable Good Good highly vigorous Over 170 Good Preferred Preferred

* Proposed for grapes in central Washington.

11 Summary Any consideration of producing grapes in Washington should take into account the market for different type grapes, the characteristics of the varieties, and their climatic adaptation. The American-type grape is the most extensively grown. It is represented by the variety Concord, grown primarily for juice but, more recently, for a new type of wine, "Cold Duck." The Concord, as well as other American varieties, is a short-season crop with considerable resistance to cold, insects, and diseases. Two other types of grapes-the hybrids and European-can be grown in Washington, but they are less tolerant of extreme cold and require a relatively long, warm growing season. Under these conditions, the early maturing vari­ eties can be productive and their fruit utilized to produce high quality, relatively dry table wines. Some guidelines can be given to help identify desirable vineyard sites. They combine the vigor of the variety with the length of growing season and soil type. At best, these are only approximate guidelines. Small differences between sites can have a significant effect on grape quality. Their importance can only be determined by field testing different varieties over a number of years.

Issued in furtherance of the Acts of May 8 and June 30, 1914, by the Washington State University Cooperative Extension Service, John P. Miller, Director, in cooperation with the United States Department of Agriculture 5M172EM

12