Part 2 (1/2)
The grape seldom suffers from hot weather in a grape region. The fruit is sometimes scalded in the full blaze of a hot sun, but the ample foliage of the vine usually furnishes protection against a burning sun. At maturing time, the heat of an unclouded sun, if the air circulates freely, insures a finely finished product. Deep planting helps to offset the harmful influences of warm climates.
_Humidity of summer weather._
The grape is very sensitive to moisture conditions, and grows best in regions where the summer rainfall is comparatively light. A damp and cloudy summer brings disaster to the vineyard in several ways; as small growth of vine, small set of fruit, a crop of poor quality, and the development of the several fungous diseases. Although the grape stands drought, a superfluity of moisture in the soil may do little harm, as is shown in irrigated vineyards, but a humid air is fatal to success especially if the air is both warm and wet. Moist weather during the time of maturity is particularly disastrous to the grape, as are frequent fogs. Cold wet weather in blooming time is the grape-grower's vernal bane, since it most effectually prevents the setting of fruit. It may be laid down as a rule that the grape lives by sunlight, warmth and air--it often thrives on the desert's edge.
These considerations make it manifest that the monthly and seasonal means of precipitation must be considered in selecting a locality to grow grapes.
_Spring and autumn frosts._
The average date at which the last killing frost occurs in the spring often determines the limit in lat.i.tude at which the grape can be grown. Even in the most favored grape region of the continent, killing frosts occasionally destroy the grape crop, and there are few seasons in which frost does not take some toll. Thus on May 7, 1916, frost all but ruined the crop of wine- and table-grapes in the great grape region of northern California where frosts are seldom expected in May.
Little or nothing can be done to protect grapes from frost. Windbreaks as often favor the frost as the vine, and smudging or heating the vineyards is too expensive to be practical. In growing grapes, therefore, the commonly recognized precaution of selecting a site near water, on slopes or in a warm thermal belt must be exercised.
The limits of grape culture are also determined by early autumn frosts. The grape stands two or three degrees of frost, but anything lower usually destroys the crop. Here, again, the only precaution is to take pains in selecting the site.
_The use of weather data and dates of life events of the grape._
These considerations of length of season, humidity and spring and fall frosts make it plain that the grape-grower must synchronize these phases of climate with the life events of the grape. In particular, he must study weather data in relation to the blooming and ripening of grapes. Usually, the necessary weather data may be secured from the nearest local weather bureau, while the date of blooming and ripening may be obtained from the state experiment stations in the states where the grape is an important crop.
_Winter temperature._
Varieties of native grapes are seldom injured in America by winter-killing, since they are usually planted in climates in which wild grapes withstand winter conditions. Native varieties follow the rule that plant and climate are truly congenial in regions in which the plant thrives without the aid of man. A few varieties of native grapes fare badly in the winter's cold of northern grape regions, and the tender Vinifera vine is at the mercy of the winter wherever the mercury goes below zero. In cold climates, therefore, care must be exercised in selecting hardy varieties and in following careful cultural methods with the tender sorts. If other climatic conditions are favorable, however, winter-killing is not an unsurmountable difficulty, since the grape is easily protected from cold, so easily that the tender Viniferas may be grown in the cold North with winter protection.
_Air currents._
Currents of air are of but local importance in growing tree-fruits, but are of general and vital importance in growing the grape. The direction, force and frequency of prevailing winds are often controlling factors in the suppression of fungous diseases of the grape, and the presence of fungi often means success or failure in regions in which the grape is planted. Winds are beneficial, too, when they bring warm air or dry air, and when they keep frosty air in motion. The air must move in all grape regions, whether from canon, mountain, lake or sea. Sunlight, warmth, and air in motion are life to the grape. Sometimes winds may be detrimental; as when too cold, too bl.u.s.tering, or when they bring hail, the latter being about the most disastrous of all natural calamities. Windbreaks are of small value and are often worse than useless. Having planted his vineyard, the grape-grower must take the winds as they blow.
_Soils for grapes_
A prime requisite for a vineyard being earth in which vines will grow, successful grape-growing is eminently dependent on the selection of soil. Many mistakes are made in the great grape regions in planting on unsuitable soils, the planter going on the a.s.sumption that any soil in a grape region should be good enough for the grape. But the crust of the earth in grape regions is not all grape soil. In New York, for example, much of the land in the three grape regions is better fitted for producing crops for the mason or road-mender than for the grape-grower. Other soils in these regions are fit for vineyards only when tiled, and tiling does not make all wet land fit for tilling.
Heavy, clammy clays, light sands, soils parched with thirst, thin or hungry soils--on all of these the grower may plant but will seldom harvest.
_The ideal soil._
Grapes may be well grown in a wide range of soils if the land is well drained, open to air and if it holds heat. But without these essentials, whatever the soil, all subsequent treatment fails to produce a good vineyard. Generally speaking, the grape grows best in a light, free-working, gravelly loam, but there are many good vineyards in gravelly or stony clays, gravel or stone to furnish drainage, let in the air and to hold heat. Contrary to general belief, the grape seldom thrives in very sandy soils unless there is a fair admixture of clay, considerable decomposing vegetable matter and a clay subsoil.
The latter, however, must not come too close to the surface. Some of the best vineyard lands in the country are very stony, the stones hindering only in making the land difficult to till. Nearly all grapes require a friable soil, compactness being a serious defect. Virgil, writing in Christ's time, gave good advice as to soil for the vine:
”A free loose earth is what the vines demand, Where wind and frost have help'd the lab'rer's hand, And st.u.r.dy peasants deep have stirr'd the land.”
Cold, churlish, sticky or clammy clays are never to the liking of the grape.
Great fertility is not necessary in grape lands. Indeed, the grape is conspicuous among cultivated plants for ability to nourish itself where the food supply is scant. Soils naturally too rich produce an overgrowth of vine, the season's wood does not mature, the crop does not set, and the grapes lack sugar, size, color and flavor. Good physical condition and warmth in a well-watered, well-aired soil enable the grape to search far and wide for its food.
_Drainage._
No cultivated grape endures a wet soil; all demand drainage. A few sorts may thrive for a time in moist, heavy land, but more often they do not live though they may linger. The water-table should be at least two feet from the surface. If by chance this comes naturally, so much the better, but otherwise the land must be tile-drained. Sloping land is by no means always well drained, many hillsides having a subsoil so impervious or so retentive of moisture that under-drainage is a necessity. The texture of the land is usually improved so greatly by good drainage that the grower has little need to rely on the clemency of the season in carrying on vineyard cultivation in well-drained land.
_Soil adaptations._
In the refinement of viticulture, grape-growers find that particular varieties grow best in a particular soil, the likes and dislikes being determined only by trial, for the peculiarities which adapt a soil to a variety are not a.n.a.lyzable. Some varieties, on the other hand, the Concord being a good example, grow fruitfully in a great variety of soils. Each of the several species with their varieties has quite distinct adaptations to soils. This is taken advantage of in planting varieties on uncongenial soils after they have been grafted on a vine which finds itself at home in the particular soil. Much has been accomplished in growing varieties on uncongenial soils by consorting them with other stocks, an operation which has brought forth volumes of discussion as to the adaptabilities of cions to stocks and stocks to soils, subjects to receive attention on a later page.