This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Peaches and Nectarines are grown in many places under glass as a market crop. Of course these fruits are nearly always to be found in large private gardens, from which the surplus produce often competes in the market with that of the commercial grower. The houses in which Peaches are grown are either "lean-to" or "span". In the former case the trees are planted on the side farthest from the wall, as shown in fig. 370, the shoots being trained up wires beneath the glass, and 12 to 15 in. from it. To secure an early crop, hot-water pipes are necessary, and from four to six rows of 4-in. pipes are laid along the sides and down the centre. In the case of span-roofed houses the trees are planted along each side about 12 ft. apart, thus giving each a spread of 6 ft. on either side. The length of Peach houses varies for market work from 100 to 200 ft. and more, and small houses may be only 12 ft. wide and 6 to 8 ft. high from floor to ridge. In many establishments houses formerly used for grapes are now being utilized for Peach growing. The low prices realized for grapes of late years have brought about this change, and wherever an old Vine is cut out, a Peach or Nectarine takes its place. It is therefore possible that the Peach houses of the future may be the grape houses of the past, and may be any size up to 500 or 600 ft. long and 20 to 30 ft. wide. (See the Plate.)
Fig. 370. - Early Peach House. Scale J in. to 1 foot.
Before planting, it is advisable to turn the soil over to a depth of at least 2 ft., but 3 ft. would be better, especially if the soil is at all retentive. Stagnant moisture at the roots would be a great drawback, and can only be got rid of by deep cultivation to secure good drainage and greater warmth for the root fibres. The soil should be of a rich loamy character, if possible, and if not naturally rich in chalk or lime this should be added. Old mortar rubble is an excellent thing to mix with the soil in Peach borders; and when the young trees are well established a dressing of bone meal every second or third year, or basic slag about December or January, will be beneficial. Humus must be added by a topdressing in winter, with well-rotted manure, but to guard against acidity this should be followed in spring with a sprinkling of lime or basic slag.
To keep the shoots at a proper distance from the glass, a wire trellis with strands running horizontally and vertically, as shown in the Plate, will be necessary. These wires should be fairly stout and well strained to secure rigidity. The best distance from the glass is 12 to 15 in. This secures not only a free passage of air between the leaves and the glass, but also prevents scorching. The grower also can push his head through in places to see that the fruits are properly exposed to the ripening influence of the sun.
To secure an early crop of peaches, fire heat may be started early in January. At first very little should be given until the plants are fairly starting into growth, and a night temperature of 45° F. will be sufficient. Later on the temperature may be gradually raised to 50° when the plants are in flower, and then 55° after they have begun to set. The day temperature will be from 5 degrees to 10 degrees higher. Care must be taken not to have it too high, say above 65° F., until the young fruits are well advanced. Attention, therefore, must be given to ventilation on all favourable occasions, and the atmosphere must be kept in a fairly moist condition by watering and syringing. Each afternoon the trees should be well syringed to keep the leaves clean, to keep down red spider, and to encourage rapid growth.
During the season it will be necessary to tie in the best of the new growths for next season's fruiting, and to pinch or cut out unnecessary ones. The proper arrangement of the wires makes this a fairly simple matter with a piece of twisted raffia.
Thinning out the fruits is practised to secure a fair crop of good size, and to prevent the trees exhausting themselves too much.
Trees in small houses, planted 12 ft. apart, will ripen on an average five dozen fine fruits. This gives roughly one fruit to every square foot of the tree; and larger trees may have their fruits thinned out to the same proportion to secure good crops. It is, however, recorded that early Peach trees covering 300 sq. ft. of trellis have produced thirty-five dozen fruit. By reckoning one peach or nectarine to every square foot of glass one may estimate fairly accurately the crop of any particular house, and the same may be said of Peaches grown in the open air. First-class fruits will realize from 8s. to 20s. per dozen, while seconds may secure anything from 2s. 6d. to 5s. per dozen. The grower, therefore, who takes care of his crop and aims at securing the finest fruits is the one most likely to obtain the highest prices. In these days of keen competition the best produce not only fetches higher prices, but also sells much quicker than the lower-grade material.