Lesson 5
Pruning, supporting, and ripening in the UK
Indeterminate varieties produce side shoots in every leaf axil. Pinch these out weekly while they are small — thumb and forefinger, a clean snap. Let them grow and the plant becomes a tangled bush with diluted fruit. Train the main stem up a cane or spiral support, tying loosely every 30 cm. Determinate types like Roma need no side-shooting; let them bush naturally.
Once the plant has four or five trusses of fruit, pinch out the growing tip — usually in late July. This stops upward growth and pushes energy into ripening what is already there. In our climate, fruit set after early August rarely ripens outdoors anyway. Remove any leaves below the lowest ripening truss to improve air circulation and reduce disease pressure, especially late blight.
Ripening depends on warmth and light. Tomatoes need daytime temperatures above 21°C to develop full flavour. If September turns cold, move pots against a south-facing wall or bring them into a greenhouse or conservatory. Alternatively, pick green fruit before the first frost and ripen indoors in a drawer with a banana — the ethylene gas triggers ripening. Heritage tomatoes will not taste as good as vine-ripened, but they will taste better than supermarket tomatoes.
Numbers that matter
- Optimal ripening temperature: 21–27°C daytime
- Stop feeding: when first fruit on lowest truss begins to colour
- Pinch out growing tip: late July, after four or five trusses have set
- Days from flower to ripe fruit: 40–50 days, longer for heritage beefsteaks
Weekly pruning and training
- 1.Check every leaf axil for side shoots; pinch out while small.
- 2.Tie the main stem loosely to the support every 30 cm.
- 3.Remove any leaves touching the compost surface.
- 4.Once four or five trusses have set fruit, pinch out the growing tip.
- 5.In late August, remove all leaves below the lowest ripening truss.
If you want to save seed from heritage varieties, let one fruit ripen fully on the plant, then ferment the seeds in water for three days before drying — this removes germination inhibitors.