Guide to Growing Tomatoes in the Greenhouse
The tomato is the most popular of all homecrops. Some people fit in a few pots here and there, others give it a large part of the greenhouse. Although the tomato is easy to grow, it can be affected by a variety of problems, but many can be avoided, as they generally arise when the crop is grown in the ground soil for several years. Excellent plants can be grown in large pots, growing bags or other containers. The system of ring culture (see opposite) also works well. The best position for the crop is one with good light. The south side of an east-west greenhouse is ideal.
There are now many seed varieties. ‘Moneymaker’, is an old favourite but it has been largely replaced by ‘Alicante’. Don’t be afraid to be adventurous. A selection is given in the table.
Sow the seeds from late winter onwards. The ideal germination temperature is 16 C (61 F). Prick out the seedlings into 80-100mm (3-4in) pots of an approved potting compost and grow on until well rooted. The plants should then be ‘rogued’. This means discarding any that are weak, stunted or distorted, or have pale-coloured or mottled foliage, and any that have a bushy or unusually vigorous habit. Such plants are liable to prove unproductive and may be affected by diseases.
When potting the plants into their final pots, try to use at least 250mm (10in) pots. Fibre disposable pots, usually about 230mm in diameter can also be used. If the pots are too small the roots suffer from erratic changes in water availability and temperature, which should be avoided. Use an approved compost and, when potting, leave a space between the compost surface and the top of the pot. This can be topped up with fresh compost as the plant develops and the compost shrinks.
The plants need strings (use rough string) or canes for support. Train them round these in a clockwise direction. It is essential, as a daily routine, to remove the side shoots that appear at the joints between the main stem and the leaves. To obtain a good set of fruit, distribute the pollen by tapping the plants or spraying with a mist of water when conditions are bright and warm. You can also spray with a hormone setting preparation.
When fruit is ripening, avoid temperatures over 27 C (81 degrees F). With too much heat the red pigment does not form and you may get green rings, or greenish/yellowish blotches. An excellent shading product is found in Coolglass, which gives the right degree of shade for strong growth but does not cast gloom. Remove any foliage that has deteriorated, but avoid excessive defoliation as this weakens plants and can spoil the fruit flavour. Special high potassium tomato feeds are available which should be used according to the label instructions.
When plants reach the greenhouse roof, pinch out the growing tips. This allows the fruit on the plants to reach maturity and ripen before conditions become too cool. It is essential to avoid erratic changes of any kind. Keep the compost moist all the time. Feed often with weak feeds and try to prevent wide temperature fluctuations. If these points are ignored, flower shedding, immature fruit fall, blotchy ripening, split skins, sun scald, or dark-coloured rots at the stalk or flower end of the fruit may occur.
This is often used for tomato cultivation but can also be adapted for other similar crops, including aubergine, sweet pepper and. The plants are grown in bottomless rings. You can buy disposable fibre rings, about 230mm in diameter, made for the purpose. The procedure is as follows. Put down a layer of aggregate, such as clean shingle or, preferably, coarse on a strip of polythene to prevent contact with the greenhouse ground soil. The polythene should be slit for here and diere if necessary. The rings are then placed on the aggregate, which should be about 130mm (5in) thick, and filled with an approved potting compost, into which the are planted. The compost must be kept moist until the roots of the plants have reached the aggregate layer. From then on, water is applied only to the aggregate layer, which is kept constantly moist. Moisture rises up into the compost from the aggregate by capillary action. Feeding with , however, is done via the compost in the rings. The lower roots of the plants are the ‘drinking roots’ and the upper ones are the ‘feeders’. This method gives the plants a highly stable environment and lends itself well to auto-matic watering systems. It is particularly useful if you have to leave plants unattended for long periods. At the end of the season, discard the aggregate; use fresh material for the next crop to prevent pest and disease carry over.
RECOMMENDED TOMATO VARIETIES
Alicante : Good general quality and disease resistance.
Big boy : Huge fruits of fleshy texture. Excellent for slicing and for sandwiches.
Eurocross A : Similar to Moneymaker, but superior vigour and yield.
Growers pride F1 : Recommended for beginners. Good early yield. Generally useful.
Mandel F1 : Good disease resistance and generally useful. Dark red colour.
Odine F1 : Short jointed and ideal for small greenhouses. Generally useful.
Tigerella : Fruit has yellow stripes. Excellent flavour. Early. Generally useful.
Vibelco : Said to be the most disease resistant of all varieties so far.
Yellow perfection : Golden yellow fruits of exceptional flavour and quality. Must be tried.