Climate and Frost Protection

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 conditions, such as indicated above, lack of rainfall may cause a failure of proper ripening. In the cooler portions 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 reduces the injury of pests and organisms. The season of 1921 was a great vintage in Europe not only because 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 organisms 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 organisms 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 during 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 organisms. Also, it may be noted that where an excessive crop is produced due to some sequence of climatic conditions, 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 maturity 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 conditions 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.

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