Growing Fruit in the Greenhouse
To make it worthwhile growing most types of dessert fruit under glass, you really need a large greenhouse. However, it need not necessarily be expensive to run, as in many cases little or no artificial heat is required. You may be lucky enough to have an old property whose garden already contains a derelict greenhouse that could be renovated and adapted for the purpose. If you are thinking of installing one specially, a lean-to greenhouse against a south-facing wall is particularly good for fruit-growing.
Among the fruits that can be grown successfully in an unheated or cool greenhouse are peaches, apricots, nectarines, grapes, figs and melons.
Interest in grape-growing is developing alongside the increasing popularity of wine-making. A lean-to greenhouse is an excellent home for a vine, though you may have difficulty finding room in it for much else.
Usually the roots of the vines are planted outside in a border alongside the front of the greenhouse. The rods (vine stems) are then passed through a little arch made in the greenhouse base and trained up the side and over the roof. Plant in late winter (January), spacing 1-2m (4 ft) between plants, and cut back the rods if necessary to 45cm (18 in). For a single plant allow two shoots to grow freely during the first year; if you are growing several vines, allow only one shoot on each. With a solitary vine the shoots can be trained horizontally in opposite directions.
Top laterals that form can then be led vertically and all others removed. Side growth from verticals should be kept to 60cm (24 in), by pinching off the tips, and removed completely in winter. Also in winter cut back the main leading shoot (or shoots from a solitary vine) to hard wood.
In the second year wires will be needed to support the lateral shoots, and in winter cut back all these laterals to one or two buds. By the third year, you should have a good crop.
In all cases only one bunch of grapes should be allowed to each lateral, and the berries should be thinned to permit those remaining to swell and have room to develop and ripen. No winter heat is necessary, but a minimum of about 10-13°C (50-55°F) during flowering is an advantage. Ventilation must be given freely when possible to avoid trouble with powdery mildew. Consult nurseries for varieties to recommend as suitable for growing under glass.
Peaches, nectarines and apricots
These are ideally suited to a lean-to, and are generally best grown in a border at the foot of the wall and trained against it (preferably as fans), using securely-fastened support wires.
It is essential to obtain varieties suited to indoor culture and on suitable rootstocks. Since the availability of varieties tends to vary from place to place in the country, it is important that a specialist grower should be consulted before you buy; nurseries are usually pleased to advise. Dwarf peaches suitable for pots are sometimes advertised in the horticultural press. Apricots are slightly more difficult to crop well than peaches or nectarines.
Preparation of the soil border and training the vine can be carried out as for plants that are grown out of doors. However, under glass it is more important to keep the plants low-growing and to induce as many base branches as possible. Also pollination under glass may be poor if left to insects that find their way in. To be certain of good pollination it is better to tie a generous tuft of cotton wool to a stick, fluffing it up loosely as much as possible, and then lightly brushing it over the flowers — preferably about midday.
Good ventilation is vital to avoid excessive temperatures, and damping-down is necessary to keep up the humidity level. Keep all water off the blossoms and off the fruit in the ripening stage, but at other times the foliage will benefit from a spray with water.
Although often thought of as exotic, good crops of figs are easily possible. The fig is usually best grown in pots since, if given an unrestricted root-run, it can smother everything else in the greenhouse. If planted in a border, the roots should be cased in with sheets of asbestos or slates or similar material. Some varieties can be placed outdoors for the summer if grown in large pots or small tubs. Always keep the plants free from weak or untidy straggly wood. Also, for best quality figs, restrict the fruit to about three per shoot. However, in the greenhouse both the current and the previous year’s shoots will yield fruit. During active growth give the plants plenty of water and moderate feeding, preferably using a balanced, soluble feed. Since the roots are restricted this feeding must not be neglected, but neither should it be excessive as this will encourage rampant growth. Avoid high nitrogen feeds as these encourage lush, leafy growth.
For the greenhouse it is best to grow casaba melons — those usually described in the catalogues as indoor melons. The smaller cantaloupes will grow just as well in frames.
Raise them from seed in a warm propagator in mid spring (March). The plants are best grown in large pots on greenhouse staging, using any good potting compost. Supporting wires should be fastened to the side and roof of the house, from end to end, spaced 30cm (12 in) apart. From then on culture is very similar to cucumber regarding training. There is, however, a vital difference and this is that the flowers must be pollinated. To do this first identify the female flowers by the tiny fruit behind them and pollinate by picking a male flower (that has a straight stem and no swelling) and brushing off some of its pollen onto the female flowers.
After pollination you will see the melons soon begin to swell and when it is certain that they are healthy and are continuing to grow, thin them to allow only three or four to mature on each plant. You can buy special nets to support the large, heavy fruits.
The finest flavour and aroma only comes from properly ripe fruit. The end farthest from the stalk should then be slightly soft to the touch if gently pressed with the finger. During ripening it is best to reduce watering and increase ventilation. Slight shading should be given during exceptionally bright, hot weather.
Duke of York – White-fleshed; ripens in late summer (mid July).
Hale’s Early – White-fleshed; ripens at the end of summer (late July).
Early Rivers – White-fleshed; ripens at the end of summer (late July).
Lord Napier – White-fleshed; ripens in early autumn (early August).
Moorpark – Large, fine-flavoured fruit; deep yellow skins flushed with red; ripens in late summer to early autumn (mid July to early August).
Black Hamburg – For cold or heated greenhouses; produces large bunches of large, fine-flavoured, black fruit.
Royal Muscadine – For cold or heated greenhouses; amber-coloured, muscat flavoured grapes.
Brown Turkey – Hardy variety, fruiting in mid autumn (early September); large, sweet, brownish-purple fruit.
Superlative – Succulent, medium-sized fruit.
Hero of Lockinge – White flesh; fine flavour.
King George – Richly-flavoured with orange flesh.
Emerald Gem – Thick green succulent flesh with excellent flavour.