Growing tomatoes from seed is a very simple business, provided you follow a couple of simple rules without fail

Steven Desmond explains how to grow tomatoes from seed

The tomato is a simple enough creature to cultivate, but only if we understand its distinctive requirements. It needs plenty of warm sunshine, plenty of water and plenty of potassium if its fruits are to resemble the picture on the front of the packet. Most people grow tomatoes from seed.

There is a long history of grafting one form onto another to furnish disease resistance, but that’s a task for the specialist. Several firms advertise grafted plants sent out in due season to those who prefer this method. For the seed-sower, scrupulous cleanliness is the key. Let your trays be clean and your fresh compost free-draining.

All the compost needs to do at this stage is support the emerging seedling. Write your labels, fill, level and firm the  compost in the tray and sow the seed. Do this evenly and thinly, so that no two seeds touch, remembering that a trayful of seeds will produce several hundred plants. There are limits to even your needs. Use a fine riddle to cover the seed loosely. Insert the label and stand the tray in an inch of water so that it’s taken up by capillary action. You will know the job is complete when the surface begins to glisten. Drain on a hard surface and set aside.

You shouldn’t need to water again until the seedlings are removed. For germination, a warm, bright setting is required—a heated glasshouse bench is ideal. If you can maintain a minimum base temperature of 21°C, so much the better.

Once the seedlings are through, you will see the need for bright light. If the seedlings don’t get it, they will bend endearingly to one side in search of it. The twin cotyledons will appear first, followed by the first recognizable true leaves. This is the time to prick the seedlings out. Handling each by the cotyledons, transfer it to a 3in pot of potting compost, making sure that the cotyledons rest just above the surface of the compost. Water well and do so every day from now on. The heat-and-light regime remains the same.

When the young plants begin to fill their pots—it won’t take long—transfer them to their final quarters. In a glasshouse, this will typically be in a growbag of some sort. This is a convenient way of growing the plants to maturity in a reasonably disease-proof environment. Tomatoes are remarkably prone to a wide range of diseases and pests.

Water copiously on a daily basis and, at an early stage, begin to supply a high level of nutrients in the form of a liquid feed. Tomatoes need a high-potassium fertiliser. There is no shortage of proprietary mixtures readily available. As the plants grow, they will need support.

If they are to grow on a single stem, make a simple loop of string loosely round the base of the stem and run it up to the glasshouse roof, one for each plant. A quick twizzle every few days provides an ideal system. As side shoots begin to form at the nodes, bend each down and remove it: do this every day.

If bush plants are preferred, a simple cane will do the job. At all times, avoid the temptation to shade the glasshouse. Do that for cucumbers, but never for tomatoes. Soon, the distinctive yellow flowers will appear. As you walk through the glasshouse, ping each string with your finger as you go by. This will help pollination. As the fruits start to develop, keep your watering and feeding steady and regular or problems will result.

On hot days, open the vents and keep the door open to promote a flow of fresh air. If things get stagnant, fungal diseases will flourish. If whitefly appears, apply a pyrethroid insecticide as soon as possible. An alternative is biological control using Encarsia parasites, but that is another job for the specialist and only works well on a large scale.

It is, of course, possible to do all this on a much smaller and more diverse basis, perhaps in pots along a terrace. The principles are essentially the same. Bush plants are more suitable. Fruiting will be later and considerably more erratic, but then pest levels will be correspondingly reduced.

The great thing about all this is that, as long as you follow the basic rules, tomatoes are a relatively simple crop to grow and everyone who does so seems to derive a great deal of satisfaction from it. Good luck with the green surplus in the autumn.

** Read more gardening tips from Country Life