Growing Fruit and Vegetables in the Greenhouse

Growing food crops in the greenhouse can be very worthwhile financially. There are also other important benefits. You can be sure of a fresh supply that has excellent flavour and texture, is high in vitamins and conveniently at hand at any time. Useful food crops can be grown all year round and, with careful planning, you can usually fit them in with most of your favourite decorative plants, thus getting the best of both worlds.

For home greenhouse gardeners it is important, as we have already seen, to avoid using the ground soil for growing. You can grow most food crops in containers of some kind. Proprietary growing bags and growing boards, which swell up after the addition of water and are easier to transport, are very popular now. Since some crops need quite a large quantity of compost, DIY mixes of peat and grit, with added proprietary, premixed balanced fertilizers, can be made up for economy.

Most food crops require good light conditions. In gloom they may crop badly and have poor quality and flavour. Glass-to-ground greenhouses and those sited in open, light positions, usually give best results, especially for winter crops.

Even the most efficiently run greenhouses are liable to invasion by pests and diseases. If you use pesticides on food crops, make a special point of reading the labels carefully. Some are safer than others; some are too toxic and not suitable at all. The edible safety period for harvesting after treatment must be noted and followed exactly.

Most of the edible crops are cheaply raised from seed. The sowing technique is much the same as that for decorative plants.

Electric soil-warming cables can be extremely useful in growing some crops. They are invaluable for warming frames in the greenhouse and for gently forcing winter and early salad crops. They can also be used to provide a little extra root warmth for various other crops so that you can enjoy them earlier.

AUBERGINE

This is grown in much the same way as the sweet pepper, but it needs a strong cane to support the heavy fruits. Allow only two or three fruits to mature per plant; pick the others off as early as possible. The young plants can be ‘stopped’ to encourage short bushy growth but this delays cropping. The plants can grow to about lm (3ft) without ‘stopping’. Grow them in large pots or growing bags. The variety ‘Early Purple’ can be recommended. It is best to pick the ripe aubergines while the ‘bloom’ or shine is still on them because when this goes they begin to have a bitter flavour.

CABBAGE AND CAULIFLOWER

The cabbage varieties ‘Hispi’ and ‘May Star’ can be sown January/March for planting out later and harvesting from May onwards. Transfer seedlings, initially, to small pots for growing on. In very cold areas, autumn sow and plant out in early March.

Cauliflowers for starting under glass must be chosen carefully from those varieties sold for sowing in September and harvesting May/June. Winter cauliflower (curding broccoli) can be sown April/May for cropping January. There are both hardy and less hardy varieties. Select according to your greenhouse temperature. Keep plants in frames during the summer. When moved to the greenhouse, space them 450mm (18in) apart.

CAPE GOOSEBERRY

This plant is related to the garden ornamental Chinese lantern. In the greenhouse it is cultivated for the golden-yellow berries that develop inside the lantern-shaped husks. The berries are about the size of large cherries and golden yellow when ready to eat. They have a pleasant, refreshing flavour eaten raw and can also be cooked and used in preserves.

For greenhouse culture choose the variety ‘Golden Berry’. Grow the plants at first in the same way as tomatoes. Use the same size pots and place in a light position. The height to which they are grown can vary considerably. You can ‘stop’ the plants at an early stage to encourage bushy growth and to get more fruits, but avoid too much ‘stopping’ since it may delay fruiting. The main harvest should be about late summer.

The true Cape gooseberry is Physalis peruviana (P. edulis) but, as grown, other species may be involved.

CLIMBING FRENCH BEAN

The ideal minimum temperature for this crop is about 13 C (55 degrees F) – it’s wise not to start it too early in the year. Late winter is probably the best time. Grow the plants in the same way as tomatoes and in the same position, spacing 350mm (14in) apart. Provide strings for the plants to climb up, and ‘stop’ the laterals and secondary laterals (side shoots) at the third joint. A recent new variety recommended for the greenhouse is ‘Selka’. The crop should be mature by late spring. Gather at once for best flavour and clear the site which can then be used for tomatoes.

CUCUMBER

The home-grown cucumber can far excel the shop-bought product. The flavour, crispncss, and digestibility of modern varieties are excellent and, nowadays, they are easy to grow; there are all-female varieties needing little attention to prevent pollination (see below), there are new pesticides available that do not harm the cucumber family in general. The crop can be grown alongside other plants including tomato. There is also often greater tolerance of low temperatures.

Ordinary varieties bear both male and female flowers and it is vital to prevent pollination of the females. Do this by promptly picking off the male flowers, which are the ones without tiny fruits attached. If pollination occurs, the fruits will go to seed, becoming club-shaped and sometimes bitter in taste. The ‘all-female’ varieties produce few, if any, male flowers and, although the seed is more expensive, the yield and flavour is usually far superior.

Sow the flattish seeds on their sides in small pots. Early March is a good sowing time. Germination occurs in a few days at about 18 C (64 degrees F). Grow on in small pots in the same way as tomatoes, subsequently planting into large pots or growing bags. If you want only a few fruits, the plants can be trained up canes. Training properly on strings should ensure cropping over a long period.

For proper training it is best to set the growing containers at staging level. The roof above should be fitted with strings running lengthways about 200mm (8in) apart. At first, grow the plants as a single stem up the greenhouse side with canes for support. Remove all side shoots. When a plant reaches the roof, lead it under the strings. Laterals which then form should be led along the nearest string. By the time four leaves have formed, the female flowers should also have developed. Now ‘stop’ the shoot. Secondary laterals will now grow out and can be secured to a string and treated in a similar manner. The main stem should be ‘stopped’ when it has reached the uppermost string.

Keep the compost moist, but be very careful not to Over-water. Wet conditions quickly cause deterioration, leaves go yellow and fruits start to rot, or drop while immature. The best quality is obtained when plants are grown so that the fruits form and mature quickly.

FIG

Given a free root run, figs can become far too rampant and invasive for the home greenhouse, so it’s wise to grow them in large free-standing pots or small tubs. This way die plants can be put outdoors in summer, which saves space and seems to improve the crop. However, some people do prefer to fan-train them against the wall of a lean-to, which should preferably be south facing. The most popular variety is ‘Brown Turkey’. This is available, container grown, from garden centres. The best planting time is spring. When the fruit is borne, ‘stop’ the fruit-bearing shoots about four leaves beyond, and allow only about three or four fruits per shoot to develop. The fruits are upright as they develop. When they hang down they are ripe and can be picked. Prune in spring, cutting out weak or excessive growth.

GRAPE

The grape vine is not a good companion for other plants. It does not want heat in winter and it can also severely cut out the light level. The best management can be given when the plant has a house to itself. Lean-tos make particularly good vineries.

The traditional way to grow the vines is to plant the roots outside the greenhouse, in a border running alongside. The stems, called ‘rods’, are then led through small holes made along the base and up inside the greenhouse. The roots can be put inside the greenhouse, but various troubles due to drying out and soil sickness are then liable to develop. Plant early in the year and then cut back the roots to about 450mm (18in). For the average greenhouse, allow two shoots to grow, leading them horizontally in opposite directions. The lateral shoots that grow from these can be trained vertically. Shoots from this upright growth should be stopped when 600mm (2ft) long, and cut back in winter. The main upright shoots should then be cut back too.

The side shoots must be fastened to wires in the second year and all laterals reduced to one or two buds in winter. A few bunches of grapes may appear in the second year, and the third year should bring a good crop. However, do not allow more than one bunch to form on each lateral. The bunches must be thinned. Do this with finely tipped scissors, without touching the grapes with your fingers as this spoils the ‘bloom’.

No heating is necessary in winter but during flowering try to maintain a minimum temperature of 13 C (55 degrees F). Efficient ventilation is essential to deter mildew, which is a common problem.

Although vines are now container grown and sold by garden centres, it’s advisable to buy from a specialist grower who will also suggest suitable varieties.

Grape vines can be grown in pots. ‘Royal Muscadine’ and ‘Black Hamburgh’ have long been cultivated in this way. The vines are potted at Christmas and put outdoors at first. In late winter they are taken into the greenhouse where no heating is necessary. They are trained on a pair of vertical bamboos, up one and then down the other. Laterals must be thinned to about 300mm (12in) apart and ‘stopped’ two leaves from where a bunch of grapes develops. You receive only about six bunches per plant and the plants have to be discarded after three years.

KIWI FRUIT

Also known as the Chinese gooseberry, this is becoming more widely available in fruit shops. It is a brownish, furry, elongate fruit about the size of a large egg, and is quite delicious. Actinidia chinensis makes a good wall shrub for a lean-to greenhouse or conservatory. Buy the plants from a specialist nursery in pairs – a male and a female. The former is needed for pollination and can be planted outside the greenhouse provided it’s close by. Insects will then usually visit both plants, but to be sure of fruit, you can hand pollinate the creamy-yellow female flowers using fluffed-up cotton wool. Plants can also be grown in large pots. ‘Stop’ them when young to produce branching for wall training. Prune in February.

LETTUCE

This crop can be grown in the greenhouse for gathering from winter to spring. It is essential to choose suitable varieties (see below) since some are quite unsatisfactory for cultivation under glass.

Lettuce can be grown in troughs or trenches of especially prepared compost or in pots. Some people use ground soil but the crop is often then attacked by grey mould, which causes die plant to wilt or collapse.

Sow the seed. Prick out the seedlings into seed trays for growing-on and transfer them to permanent positions when large enough to handle. Give good light and ventilation.

The variety ‘Kwiek’ is suitable for a cold greenhouse, and should be sown in late summer to crop in winter. ‘Kloek’ can also be grown in cold conditions but should be sown in autumn for spring use. ‘Sea Queen’, which can be grown in either cool or cold conditions, is sown in late summer or winter for winter or spring cropping. ‘Emerald’ can be treated similarly. Sow ‘May Queen’ in autumn or spring in a cold or cool greenhouse for spring or summer cropping. ‘Dandie’, which is a fast maturing variety, can be sown in autumn to give you a good crop from late autumn onwards.

MELON

The best melons to grow in the greenhouse are the very large Casaba types. The small kinds, such as Musk or Cantaloupe, are more suitable for frame culture.

Treatment is the same as for cucumber in the early stages. The training is also similar, but differs in that the strings for support, which must be strong, should be spaced further apart, about 300mm (12in). The female flowers must be deliberately pollinated. Do this by removing a male flower, which is one with no swelling behind it on the stalk, and transferring the pollen directly to the female flowers, which have die swelling. Successful pollination is indicated by the swellings becoming larger and soon taking the form of tiny melons.

Melons need plenty of light and there is rarely need for shading. Allow only three to four fruits on each plant. When the fruit has matured, avoid excessive humidity and ventilate more freely than before. Owing to their weight, the fruit may need supporting with netting; you can improvise with string bags. Fruit is ripe when the opposite end from the stalk feels soft when you press it with a finger; and when it gives off a fruity aroma.

Recommended varieties are ‘Superlative’, ‘Hero of Lockinge’, and ‘Emerald Gem’. The Cantaloupe melon, ‘Early Sweet’, is a vigorous F1hybrid and larger than others of this kind. It can be grown like the Casabas. Of the Cantaloupes the variety ‘No Name’ is especially recommended for unheated frames. Sow and raise initially in the greenhouse.

MUSHROOM

The mushroom is the fungus Psalliota campestris.

It is a useful crop for the understage area, if a temperature of about 10 C (50 degrees F) minimum can be maintained. The area can be sectioned off and heated with soil warming cables for economy, if desired. Mushroom growing is normally an elaborate procedure requiring special composts and spawn. However, it is now made easy by the availability of ready-spawned ‘buckets’ stocked by most seedsmen. Full instructions, which are quite simple, are provided. You can obtain a constant supply of fresh, delicious mushrooms using this method, but they may not be cheap.

PEACH, NECTARINE, APRICOT

These, like the grape, are not generally suitable for growing in a mixed greenhouse collection. The ideal site for them is the rear wall of a south-facing lean-to. They are grown in much the same way as other wall-trained outdoor plants, except that hand pollination is usually required. This is simply done by brushing over the flowers lightly with a piece of fluffed-up cotton wool. Midday is the best time to do it.

If you grow them in the greenhouse, keep the atmosphere moderately humid by damping down, but do not spray the flowers with water. Apricots can be tricky and the flowers tend to drop if the temperature rises high and ventilation is inadequate. Contact a specialist nursery when buying die plants. Recently there have been new varieties introduced and also especially dwarfed forms, which are ideal for growing in pots or limited space.

Some old-established varieties are ‘Lord Napier’ and ‘Early Rivers’ (nectarine); ‘Moor-park’ (apricot); ‘Hale’s Early’ and ‘Duke of York’ (peach).

SPROUTING SEEDS

Seed sprouts (salad sprouts), which include a variety of plants, have recently received much publicity because of their possible health-giving properties. In particular, they often have high vitamin and protein content and in some cases minerals too. They are delicious, and in winter, salad sprouts can be especially welcome. You can produce an edible crop within about one week.

Many seedsmen offer packets of seeds suitable for sprouting and supply full instructions. The best place to grow them is in a propagator. A temperature of about 20 C (68 F) is desirable, which can be attained in most simple propagating cases. The old favourite, mustard and cress, is included in this group. You can also sprout mung bean (Phaseolus mungo) well known because of its use in Chinese cooking, alfalfa (Medicago sativa) particularly valuable for winter salads, adzuki beans (Phaseolus angularis) with a nutty flavour, and fenugreek (Trigonella foenum-graecum).

SQUASHES

These include courgettes, marrows, and pumpkins. They are not usually cropped in the greenhouse, but the sowings and initial growing of the young plants can be made under glass to ensure earlier crops. Don’t forget to harden off the young plants before putting them outdoors.

STRAWBERRY

These are really most suited to frames but a few pots can be grown in the greenhouse. They look good planted in special strawberry urns, which are available at most garden centres. Buy the plants freshly each year from a specialist grower who will have the fine modern varieties. Grow them on outdoors until early in the year. Pot up in an approved compost, one plant to each 130mm (8in) pot if desired. The best minimum temperature is 7 C (45 degrees F). Hand pollinate by brushing over the flowers lightly with fluffed-up cotton wool.

30. August 2013 by admin
Categories: Featured, Garden Management, Top Tips | Tags: , | Comments Off on Growing Fruit and Vegetables in the Greenhouse

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