Tomatoes grow very successfully in grow bags in a greenhouse or outdoors. Crops can be improved by inserting bottomless pots full of soil into the grow bag to increase the volume for better root growth. Buy young plants in late spring, or sow seed indoors earlier in the season.

When to start: Mid-spring.

At their best: Early autumn.

Time to complete: 2 hours over a few months.

You will need: Two tomato plants, grow bag, two plastic pots, stanley knife, some extra soil, stake (bamboo cane or chestnut stake), garden twine.

Varieties to try: ‘Black Russian’, ‘Gardener’s Delight’, ‘Marmande’, ‘Shirley’, ‘Summer Sweet’ F1, ‘Sungold’ F1.

Cut out holes

Cut the bottom off the pots, then place them on the grow bag and cut around them. Push the pots into the bag and fill them up with the spare soil.

Plant into the pots

Plant one tomato per pot at the same level as it was growing in its container. Plant straggly plants a little deeper. This encourages new roots to form along the buried stem, helping stabilize the plants.

Pinch out sideshoots

As the plants grow, small sideshoots appear off the main stem. These should be removed as soon as possible because they will take energy away from the ripening fruits. When they are small, simply pinch them out with your fingers.

Tie in main stems

Tomato plants need to be regularly tied in to a sturdy support. Make a figure-eight knot using twine, tying tightly around the support, and loosely around the plant stem, to allow room for growth.

Nip out the top

You can help the plant put all its energy into ripening the fruits by preventing it from putting on too much growth. After outdoor plants have set four trusses of fruits, and greenhouse plants six, nip out the top shoot with your fingers.

FRUITING AND HARVESTING

Tomatoes are best when picked fully ripe, but you are likely to have some green tomatoes at the end of the season. Cutting back on watering can help shock the plant into ripening the fruits. If it is getting cold and your tomatoes must be harvested, pull up the whole plant and hang it by its roots somewhere cool and dark to finish ripening.

Tips: Careful watering

Cracks can appear in the skin just as fruits are ripening. The problem is due to changes in growth rate, caused by fluctuating temperatures and erratic watering; as growth slows during a cool, dry period, skins harden and do not have the elasticity to cope if growth later picks up and fruits swell. It is a particular problem in soft-grown plants: those that have been fed too much nitrogen.

While you cannot control temperatures, you can make sure watering is regular, and that you provide the correct feeding regime. Make provisions for watering if you go away, even for a few days, and feed weekly with a specially formulated tomato feed, one rich in flower-and fruit-promoting potassium.