Manual of American Grape-Growing. U. P. Hedrick
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 cañon, 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 blustering, 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 assumption 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 sturdy 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 analyzable. 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.
Insects and fungi
The profitable grape regions of the country have all been established in regions comparatively free from grape insects and fungi. If pests came later in considerable numbers, the industry, in the old days, perished. Here and there in the agricultural regions of the country may be found a sorry company of halt and maimed vines, remnants of once flourishing vineyards, brought to their miserable condition by some scourge of insects or fungi. The advent of spraying and of better knowledge of the habits of the pests has greatly lessened the importance of parasites as a factor in determining the value of a region for grape-growing; but even in the light of the new knowledge, it is not wise to go against Nature in regions where pests are strongly intrenched.
Commercial factors
The dominant factors that lead to the planting of large areas to any one fruit are often economic ones; as transportation, markets, labor, facilities for making by-products, and opportunity to join in buying and selling organizations. All of these factors play an important part in determining the bounds of grape regions, but a lesser part than in the establishment of large areas of other fruits, for the reason that the grape is so largely grown for raisins, wine, champagne and grape-juice, products condensed in form, made with little labor, easily transported, which keep long and find ready market at any time. Again, where natural conditions are favorable for grape-growing, the crop comes almost as a gift from Nature; whereas, if the grower must breast the blows of unfavorable natural circumstances, no matter how favorable the economic factors may be, the vineyard is seldom profitable. Natural factors, therefore, outweigh economic ones in grape-growing, but the latter must be considered in seeking a site for a vineyard, a task discussed under several heads to follow.