Manual of American grape-growing

by U. P. Hedrick

Plate XV.—Eclipse (×2/3).

CHAPTER XI

GRAPES UNDER GLASS

Grape-growing under glass is on the decline in America. Forty or fifty years ago the industry was a considerable one, grapes being rather commonly grown near all large cities for the market, and nearly every large estate possessing a range of glass had a grapery. But grapes are better and more cheaply grown in Europe than in America, and the advent of quick transportation permits English, French and Belgian grape-growers to send their wares to American markets more cheaply than they can be grown at home. For the present, the world war has stopped the importation of luxuries from Europe, and American gardeners ought to find the culture of grapes under glass profitable; they may expect also to be able to hold the markets for many years to come because of the destruction of Belgian houses and the shortage of labor in Europe resulting from the war.

Amateur gardeners ought never to let the culture of grapes under glass wane, since the hot-house grape is the consummation of the gardener's skill. Certainly the forcing of no other fruit yields such generous rewards. Grapes grown under glass are handsomer in appearance and better in quality than those grown out-of-doors. The clusters often attain enormous size, a weight of twenty to thirty pounds being not uncommon. The impression prevails that to grow grapes under glass, one must have expensive houses; this is not necessary, and "hot-house grapes" is a misnomer, the fruit really being grown in cold or relatively cool houses which need not be expensive. Grapes are grown under glass with greater ease and certainty than is imagined by those who form the opinion from buying the fruit at high prices in delicatessen stores. A grapery need not be an expensive luxury, and the culture of grapes under glass can be recommended to persons of moderate means who are looking for a horticultural hobby.

The Grapery

Almost any of the various modifications of greenhouses can be adapted to growing grapes. Firms constructing greenhouses usually have had experience in building graperies, and, as a rule, it will pay to have these professional builders put up the house. If the actual work is not done by a builder, it is possible to purchase plans and estimates, from which, if sufficiently detailed, local builders can work. On small places there is no doubt that the lean-to houses are most suitable, being inexpensive and furnishing protection from prevailing winds. These lean-tos should face the south and may be built against the stable, garage or other building; or better, a brick or stone wall to the north may be erected. It is possible to build a small grapery as a lean-to out of hot-house sash.

In commercial establishments and for large estates, where the grapery must be more or less ornamental, a span-roof house is rather better adapted to the grapery than a lean-to, especially if the house is not to be used for the production of grapes early in the season. On account of the exposure of the span-roof house on all sides, however, rather more skill must be exercised in growing grapes in them than in the better protected lean-to grapery. Whatever the house, it must be so constructed as to furnish an abundance of light, a requisite in which much is gained by having large-size glasses for the glazing. The glass must be of the best quality, otherwise the foliage and fruit may be blistered by the sun's rays being focused through defective spots.

Light, heat, moisture and good ventilation are all required in the grapery. Brick or stone are preferable to woodwork, as heat and moisture in the grapery are quickly destructive to wood foundations. If wood is used, only the most durable kinds should enter into the construction of the house. The under structure of masonry or of wood should be low, not higher than 18 inches or 2 feet before the superstructure of glass begins. The grapery must be well ventilated. There must be large ventilators at the peak of the house and small ones just above the foundation walls or in the foundation walls themselves. The ventilation should be such that the house can be kept free from draughts or sudden changes of temperature, as the grape under glass is a sensitive plant, and subject to mildew. Plenty of air, therefore, is an absolute necessity to the grapes, especially during the ripening of the fruit. The lower ventilators in graperies are seldom much used until the grapes begin to color, at which time the new growth, foliage and fruit are hardened, but from this time on upper and lower ventilators must be so manipulated that the houses are always generously aired.