The Grape Vine (Vitis vinifera)
The Grape Vine (Vitis vinifera)
Ideallyshould be planted in a specially prepared border either inside or just outside the greenhouse, the stem being led in just above ground level and the roots able to spread freely and derive benefit from rainfall. Culture in large pots or tubs 30cm (12in) or more in diameter may be an excellent arrangement for the smaller greenhouse.
Preparation of vine borders
A vigorous vine will demand a section of greenhouse border at least 90cm-1.2m (3-4ft) wide and 1.8-2.4m (6-8ft) long with a prepareddepth of 60cm (2ft) or more. It would be folly to try to grow a vine in a diminutive structure.
The preparation of a vine border in traditional pattern is exacting in the extreme, demanding (1) complete removal of the soil to a full depth of 75cm (2ft 6in), (2) a 15cm (6in) layer of rubble or broken brick with(it is sometimes advisable to dig much deeper and arrange for an in situ sump of rubble), (3) a layer of inverted turves, (4) a mixture of 5 parts good sifted loam, 1 part mortar rubble (if not procurable broken brick will suffice), 1 part decayed manure, and any wood ash which may be available, (5) 68 —136g/m2 (2-4oz per sq yd) of bone meal and, if mortar rubble was not used, 270-400g/m2 ground limestone (½ – ¾ lb per sq yd). This compost was used over generations; it may not be practicable now. Good soil plus a little manure can be used instead, so long as good drainage is provided. John Innes Potting Compost 3 is used when planting in large pots or other containers.
When placing the roots out of doors the same procedure should ideally be followed for the make-up of the bed, but the same compromise may have to be made, with attention again to drainage. The idea that the carcass of a dead animal forms a good foundation for a vine may be true, although it is a practice seldom acceptable.
Propagation and planting
Vines are frequently bought as young roots, although they can readily be propagated from 5cm (2in) ‘eyes’ taken in late winter and put in a pot with the ‘eye’ at soil level. Also layers, 3 bud stems, or young growths. Given heat, young plants are ready for setting out in early or midsummer of the following year.
Dormant vines are usually planted between mid-autumn and late winter anything from 1.5-3m (5-10ft) apart according to the system of training employed. For a single cordon 1.5m (5ft) apart will suffice, but one vine is usually sufficient for the amateur greenhouse. If the greenhouse is oriented with the ridge running north-south it would be advisable to plant the vine in the centre or to one side of the north end. This will allow the vine to travel along the one sloping roof and, provided it is ruthlessly restricted, still allow the culture of other crops. A better arrangement can be made if the greenhouse is oriented east-west, when the vine could then be trained along the north side and largely confined to this to avoid the restriction of light from the southerly aspect (ie if in the northern hemisphere). Where the whole greenhouse can be devoted to the culture of the vine, then the centre at the end away from the door is as convenient a location as any. In lean-to structures it is usual to train vines on the glass side.
Support is usually provided by a series of wires run horizontally 20-25cm (8-10in) apart through wire eyes screwed into the astragals (glazing bars). Alternatively, mesh materials can be used. With an alloy house it will be necessary to make a wooden framework or use sucker supports.
The vine, self-raised or bought, is taken out of its pot and the roots opened up or disentangled, it not being advisable to leave them in a compact ball. It is then planted into container or border by spreading out the roots well, setting not too deeply, watering in and, after a good firming, mulching the surface of the soil with peat or well-rotted farmyard manure. When the root is planted out of doors it will be necessary to remove a brick or two, or a section of glass or wood, keeping the opening to a minimum and covering one root and wrapping the stem with sacking and filling any air space with straw and sacking.
Pruning and training
Dormant vines must be cut back to 1.2 or 1.5m (4 or 5ft) after planting; a young growing vine planted in summer is cut back to two buds after planting. Strong growth should invariably result, encouraged by plentiful watering and spraying the young leaves and stems. In the small greenhouse there is much to be said for allowing only one main rod, but vine rods are very accommodating and at any stage the decision can be altered and another ‘main’ growth allowed to develop.
In the winter subsequent to planting new growth on the main rod or rods is cut back to 90-1.2m (3 or 4ft) and any lateral shoots to two plump base buds which can readily be found if searched for, although not obvious.
Annualfollows the same general pattern of cutting back a proportion of new growth, although there will come a time when this cannot be achieved and the vine has to be restricted according to space available.
The number of laterals must be determined at a fairly early stage, it generally being convenient to have a lateral running off about every 60cm (2ft) of rod. It is also important to decide in which direction the shoots are to be allowed to form; if the main rod is run along under the ridge of the greenhouse the laterals can be tied down one side to the gutter, or the other way round.
It is general practice to allow the vine to become established over two or three years before any fruit is allowed to form, but in the restricted conditions of amateurit would seem futile to carry out this practice, it being more desirable to restrict the vigour by early cropping or any other means, always provided of course that the vine has at least enough root system to sustain growth. After cutting back the laterals to two plump buds, two shoots are allowed to form each spring; the stronger and preferably the one bearing a bunch of embryo fruit is selected, the other being removed completely. This procedure is followed (spread out over a period to avoid shock) at each lateral growth point until in the end the single, double or treble rod is left with a number of single laterals growing out in one or both directions.
The laterals are gradually pulled in to the supporting wire or mesh material and tied, progressively shortening the string used. The tip of each lateral should be nipped off at the second leaf past the bunch of grapes, or if no grapes, as with a young vine, the lateral is stopped at about the seventh leaf. Sub-laterals formed after stopping are restricted to one leaf or so, although this is not critical. No system of pruning is rigid; it must be adapted to circumstances and space.
Early vines will start into growth by mid-or late winter in the greenhouse if there is sufficient heat. Withgrowth will start later. Water is applied to the roots, and the vents are shut a little to encourage a humid atmosphere, while the rods may be syringed well with plain water. In order to get an even break of buds it may be necessary to arch the leading shoots over by untying the rod from its support, but with younger vines this is seldom necessary. -When the appear the greenhouse should, if possible, be kept drier, ceasing syringeing and avoiding damping down. Pollination and fertilization generally occur readily, but it may be necessary to tap the rod or dust the flowers with a little cotton wool on the end of a cane.
Vines should never be allowed to dry out. Borders should be watered with a fine rose, keeping the surface moderately moist, and a good thick mulch of peat will assist in this direction. Vines growing in pots or boxes must be watered regularly, indeed this is one of the main disadvantages of growing them in this manner.
About 12.8°C (55°F) is satisfactory for flowering, and for rapid swelling of the berries the ideal is 18.3°C (65°F) day and about 15.6°C (60°F) at night. Feed with weak liquid manure at this stage. During ripening plenty of air should be given to avoid botrytis. Vines will resent sudden temperature changes just as much as any other crop, and can react very positively by `’, when the stems of the berries shrivel or the berries ‘scald’. Ideally a little air should be left on at night always, particularly when the berries are ripening.
Thinning and harvesting
The thinning of grapes is most important. A start should be made when the berries are about the size of peas, using special vine scissors and leaving the berries about half an inch apart. Success at shows depends much on the shape of a bunch of grapes and a little practical experience goes further than pages of description. A few weeks after thinning the rapidly swelling berries appear to stop growing, this being because they are -stoning, and ibealty the temperature should be dropped a little during this period. It is important not to allow too many bunches of grapes to remain on a vine, about 2.5kg per m (1lb per foot) or rod being usual. The bunches will ripen according to variety, temperature and season, and should be harvested when ready; in a cold greenhouse in a northerly latitude there can be difficulty in fully ripening the grapes of some varieties such as ‘Black Hamburg’.
Winter pruning follows the sequence described previously and should be carried out annually when the vine is dormant. After pruning lift all dead leaves and rubbish and then rub all loose bark from the main rod of the vine and paint with a strong solution of malathion, or other general insecticide, avoiding the buds which can otherwise be damaged. This procedure is to kill off over-wintering pests.
The border should be given a good top dressing of well-rotted farmyard manure annually, and in addition a dressing of 101-136g / m2 (3-4oz per sq yd) of a good balanced general fertilizer as growth commences.
For heated greenhouses: Alicante (black), Black Muscat, Gros Colmar (black), Lady Downes (black), Madresfield Court (black), Muscat of Alexandria (white), White Frontignan.
For cold or cool greenhouses: Black Hamburg, Buckland Sweetwater (white), Fosters Seedling (white), Forbes Seedling (white), Gros Maroc (black), Reine Olga (reddish).