Some Tips on Tomato Growing Under Glass

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Tomato Growing Methods

If growing in soil in the bed of the glasshouse, I must emphasize that not any old garden soil will do. I have grown a large amount of runner beans in the same area and over the years this has given me a lovely soil, full of nutrients as I incorporate large amounts of leaf mould and rotted manure into the trenches. The soil from one of these trenches was transferred into one side of the glasshouse.

Then a dressing should be applied, blood, fish and bone at approximately 5oz per yard run and calcified seaweed, also at 5oz per yard run. Add a light dusting of lime to keep things sweet, tomatoes like a little lime. Work this into the top few inches and all is ready to receive the plants.

Another very good way to grow them is in bottomless rings on top of grow bags. This gives them twice the depth of compost. The only drawback with this method is that in a very hot summer they require constant watering, while those grown in soil in the greenhouse bed have unlimited room for roots to forage for water and nutrients and do not need such constant attention. On the other hand, if you grow in the greenhouse bed, the soil that the plants grow in should be changed every three years. If left longer than this, you run the risk of disease.

Sowing & Pricking Out Your Tomatoes

I sow my first seed in February, for early picking. Another sowing is made in March for late season use. The seeds are started off under heat in a peat-based compost.

When your seedlings start to show the true tomato shaped leaf, prick out into three inch pots. Drop your seedling in up to the bottom seed leaf; this makes for a sturdy thick stem instead of a thin weakling due to not pricking out deep enough. Keep the seedlings in plenty of light until they are about six to eight inches high and ready for planting into the bed.

Supporting the Tomatoes

There are various methods of support, the best of which is a bamboo cane secured to a cross wire running along the apex of the house. You could also use stout nylon cord, twisting the cord about the plant as it grows. The disadvantage here is that if you have a heavy crop, the plant may slip down the cord which will snap the stems at the base.

You should plant out at least fifteen inches apart, any less and you will not have enough room to get between the plants to weed and remove side shoots. It is important to feed and water regularly. Tie the plants in frequently as they grow.

Ventilation

To grow tomatoes to perfection, ventilation must take a key role; air must be able to circulate around the plants at all times. On very hot days all doors and sky-lights should be fully opened. The sign of a really well grown tomato plant is that the fruits at the top of the plant are as big as those closer to the base.

Ripening Tomatoes

Ripening of the fruit can be a problem in a cold wet summer. You may find that a food high in potash will help; you can also take off some of the leaves, but on no account must you take them off above ripe fruit. How many trusses you want on your plants is entirely down to personal preference, I have nine trusses per plant this year. Pinching out the tip of the plant will prevent any new trusses from forming.

Pests and Problems

A few problems may arise in a growing season. Blossom end rot is the most popular topic for questions. This is caused by prolonged spells without water, or irregular watering and feeding patterns and a calcium deficiency. It is more prevalent when the tomatoes are grown in grow-bags because on hot days the bags can dry out very quickly.

White fly is also a pest that needs controlling. Don't wait to be overrun by the pests, but put up some sticky yellow insect traps early in the season.

On no account should you smoke inside your greenhouse. It can play havoc by introducing tobacco mosaic virus into your plants. The only effective cure for this is to burn all infected plants, never put then on a compost heap. With good ventilation you should not run into the problem of grey mould on the leaves.

This article originally appeared in the Members Bulletin, the journal of the National Vegetable Society, which is sent quarterly to members. You can Join the National Vegetable Society here

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