Tomatoes

Overview

Tomatoes - Lycopersicon esculentum

Tomatoes fall into two categories the indeterminate or cordon type and the determinate or bush type. The cordons are grown in greenhouse although they can be grown outdoors as well. The bush types are only grown outdoors because their dwarf, sprawling habit makes them unsuitable for greenhouse cultivation.

Varieties to choose (as sold by Kings Seeds)

How to grow

Sow

Tomatoes are raised from seed. The seed is sown during February/early March for growing in the heated greenhouse and in mid-March for growing in the unheated greenhouse. Sow the seed in small pots or trays filled with fresh seed compost maintaining a temperature of 65F/18C day and night until the seed germinates; the temperature can then be lowered to 60F/16C. When the seedlings are large enough to handle prick them out singly into 4”/10cms pots filled with fresh potting compost setting the large seed leaves just above the top of the compost. The seed for outdoor tomatoes needn’t be sown until April. A general rule of thumb guide is to allow six weeks from pricking out to the final planting out.

Growing on

Greenhouse tomatoes

Wait until the young tomato plants have started to produce their first flowers before transplanting them into their final cropping positions. If they are transplanted too early they will continue to grow but only producing leaves at the expense of flowers. The young tomato plants can be planted directly in to the greenhouse border soil or two plants in a growbag. They can be grown in an 18”/45cm flower pot filled with fresh potting compost. The central stem or cordon has to be trained or supported in some way to help carry the weight of the tomato crop. The easiest method is to use a bamboo cane that is secured to the roof of the greenhouse and pushed into the soil or compost at the base. As the tomato plant grows it will produce sideshoots in the leaf joints along the main stem. As soon as they are about 2”/50mm long they must be carefully removed by snapping them off where they are attached to the stem. If this job isn’t done regularly the tomato plant will produce branches that sprawl in every direction. When the plant reaches the top of the greenhouse the growing tip has to be pinched out at the next set of leaves above the last bunch/truss intended to bear fruit. This usually works out at around four trusses in most greenhouses but if there is the extra headroom available allow them to grow on.

Outdoor tomatoes

These can only be planted out in the open soil after the chance of the last frost has gone. Usually this is towards the end of May in southern areas but in the north of the country it could be into June. Check on the local weather forecast before risking transplanting the young tomatoes outdoors. Some protection may be required during the early stages of establishment.

How to Harvest

Once the fruit are full and red, they are ready for picking and eating. However if you've got green tomatoes left at the end of the season, they can be ripened on a window sill or in a brown paper bag.

Issues

The main pests of greenhouse tomatoes are whitefly and greenfly. These can be controlled using sticky traps and the biological control Encarsia formosa for the whitefly and Aphidius for the greenfly. Both indoor and especially the outdoor tomatoes will suffer from an attack by potato blight Phytophera infestans at some stage during the summer. It is difficult to control and destroys the crop.