Feeding, watering, and the fruiting phase

Tomatoes in pots are greedy. The roots cannot forage, so you supply everything. Water daily once fruiting begins — the compost should never dry out completely but never sit sodden. Early morning is best. If the top 2 cm is dry, water. If it is still damp, wait. Irregular watering causes blossom end rot, where the bottom of the fruit blackens and collapses, especially on paste varieties.

Feed with liquid tomato fertiliser (high potash, usually 4-4-8 NPK) from the moment the first flower truss appears. Apply at half the label rate, twice per week, rather than full strength weekly — little and often keeps growth steady. Heritage tomatoes do not tolerate sudden nitrogen surges, which push leaf growth at the expense of fruit. If the plant produces lush, dark green foliage but few flowers, you are overfeeding nitrogen.

Once fruit begins to swell, increase feeding to full label rate twice per week. If leaves yellow from the bottom up, the plant is running short of nutrients. If they curl and darken, you are overwatering or the compost is too rich. Watch the plant — it will tell you.