Manual of American Grape-Growing. U. P. Hedrick
on the region for viticulture. In addition to the benefits of deep bodies of water, high and sloping lands cause the frosts to cease early in the spring and hold them in abeyance in the autumn, giving an exceptionally long season.
Champagne-making began here about 1860; at present there are a score or more manufacturers of champagne, wine and brandy, the output being annually about 3,000,000 gallons of wine and 2,000,000 bottles of champagne. Recently the manufacture of grape-juice has begun and the industry is now flourishing.
Minor grape regions.
Viticulture is commercially important in several other regions than those outlined. Thus, in the valley of the Hudson River, grapes have been grown commercially for nearly a hundred years, the industry reaching its height between 1880 and 1890, when there were 13,000 acres under cultivation. For some years, however, grape-growing along the Hudson has been on the decline. Another region in which viticulture reaches considerable magnitude is in several islands in Lake Erie near Sandusky, Ohio, the product going largely for the manufacture of wine. At one time grapes were grown commercially on the banks of the Ohio River about Cincinnati and westward into Indiana. The industry here, however, is a thing of the past. Another region in which grape-growing was once of prime importance but now lags has its center at Hermann, Missouri. The newest grape-producing area worthy of note is in southwestern Michigan about the towns of Lawton and Paw Paw. A small but very prosperous grape-growing region has its center at Egg Harbor, New Jersey. Ives is the mainstay among varieties in this region. In the southern states, Muscadine grapes are grown in a small way in every part of the cotton-belt and varieties of other native species are to be found in home vineyards in the upland regions, but nowhere in the South can it be said that grape-growing is a commercial industry.
The Determinants of Grape Regions
Climate, soil, site, the surface features of the land, insects, fungi and commercial geography are the chief factors that determine regions for money-making in grape-growing. This has been made plain in the foregoing discussion of grape regions, but the several factors must be taken up in greater detail. To bound the regions is of less importance than to understand why they exist—less needful to remember, more needful to understand. From what has been said, the reader has no doubt already concluded that successful grape-growing is in largest measure due to kindliness in climate.
Climate
Under the assumption, then, that climate, of all factors, is chief in playing providence to the grape, let us examine somewhat critically the relations of climate to grape-growing. When analyzed, the essentials of climate, as it governs grape-growing, are found to be six: first, length of season; second, seasonal sum of heat; third, amount of humidity in summer weather; fourth, dates of spring and autumn frosts; fifth, winter temperature; sixth, air currents.
Length of season.
To reach true perfection, each grape variety has a length of season of its own. With each, if it is grown in too low a latitude, the vine is uninterrupted in growth; its leaves tend to become evergreen; and not infrequently it produces at the same time blossoms, green fruits and ripe fruits. This is, of course, the extreme to which grapes pass in the far South. Again, many northern varieties fail where southern grapes succeed because the fruits pass too rapidly from maturity to decay. On the other hand, very often southern grapes are hardy in vine in the North, but the season is not sufficiently long for the fruit to mature and to acquire sufficient sugar to give them good keeping quality, properly to pass through vinous fermentation, or even to make a good unfermented grape-juice. In the uneven topography of this continent, it is not possible to state the range in latitude in which grapes can be cultivated to advantage, for latitude is often set aside by altitude. Thus, isothermal lines, or lines of equal temperature, are much curved in America and do not at all coincide with the parallels of latitude.
Other factors, of course, than length of season enter into the ripening of grapes. The daily range in temperature, not always dependent on latitude, affects ripening. Cool nights may offset warm days and delay ripening. Certainly rains, fogs and humid air delay maturity. The bottom heat of loose, warm, dry gravelly or stony soils hastens maturity. Sunshine secured by a sunny aspect or shelter hastens maturity.
The seasonal sum of heat.
Successful cultivation of the grape depends on a sufficient amount of heat during the summer season. The theory is that buds of the grape commence to start when the mean daily temperature reaches a certain height, and that the sum of the mean daily temperature must reach a certain amount before grapes ripen. Manifestly, this sum must vary much with different varieties, low for the earliest sorts, high for the latest. There have been many observations as to the temperatures at which buds of the grape start growth, so that it is now known that the temperature varies in accordance with locality and degree of maturity. Roughly speaking, grape buds start at temperatures from 50° to 60° F. The seasonal sum of heat for ripening is probably 1600 to 2400 units. A variety ought not to be planted, therefore, in a region in which the average seasonal sum of heat is not sufficiently high. The seasonal sum of heat can be determined for a locality from data published by the United States Weather Bureau; and by comparing with the sum of heat units in localities where a variety is known to thrive, the grape-grower can determine whether there is sufficient heat for any particular variety.
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 latitude 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