When and How to Feed Tomatoes
Tomatoes are hungry plants, but feeding at the right stage matters more than feeding often. Good soil, steady watering and a suitable high-potash liquid feed once fruit sets support a useful crop without encouraging excessive foliage. Adjust the routine for plants in open ground, containers, greenhouses and polytunnels.
Prepare the growing area before planting. Work garden compost or well-rotted manure into open ground during spring, taking care not to overwork wet soil. For containers, use fresh peat-free multipurpose compost with good drainage and a pot large enough for the variety. This early preparation gives roots a balanced start and reduces the temptation to feed heavily while plants are small. Plant out only after the risk of late spring frost has passed and harden plants off gradually if they were raised in a greenhouse. Water plants in thoroughly, then allow roots to establish before beginning any regular liquid feeding routine.
Wait until the first fruits have set before using a high-potash, high-potassium liquid feed. Flowers alone are not the cue; look for small developing tomatoes behind faded flowers. Feeding too early can produce lush leaves and fewer fruiting trusses, particularly if the compost is already fertile. Follow the dilution and frequency guidance for your chosen product, or use homemade comfrey feed prepared and diluted safely according to your method. Do not add extra quantities in the hope of faster ripening. Tomatoes respond best to steady care: adequate light, even moisture, warmth and sensible feeding rather than sudden rich doses.
Plants in containers need closer attention because watering gradually washes nutrients through compost. Once fruit has set, feed regularly at the stated interval while plants are actively producing, checking that the compost is already moist before applying liquid feed. Never pour strong feed onto a dry root ball, as it can stress roots and will not be distributed evenly. Water first if necessary, then apply the prepared feed to the compost surface. Greenhouse and polytunnel plants may grow quickly in warm weather, so monitor leaves, flowers and fruit weekly rather than feeding automatically when conditions are cool or dull.
Open-ground tomatoes often need less frequent feeding than those in pots because their roots can explore a larger volume of soil. Use the plant's progress and the richness of the bed as guides. If you incorporated plenty of garden compost, start cautiously once fruit sets. Pale new leaves can have several causes, including cold soil, overwatering, poor drainage or root disturbance, so do not assume more feed is the answer. Check soil moisture, spacing and light first. A healthy plant should have firm green leaves, regular flower trusses and steadily swelling fruit, not dark, overly soft foliage.
Keep watering consistent while feeding. Irregular moisture makes it difficult for roots to take up nutrients and can contribute to fruit problems. Water at the base, preferably in the morning, and mulch open-ground plants with garden compost or leaf mould to slow evaporation. In containers, check daily during warm weather and ensure drainage holes remain clear. Avoid letting pots stand permanently in water. Do not feed plants that are badly wilted until they have been rehydrated and recovered. Supporting cordon tomatoes and removing their sideshoots also directs energy into the retained flowering and fruiting trusses.
Stop escalating feed late in the season. As temperatures and light levels fall, new flowers are less likely to make worthwhile ripe fruit, especially outdoors in northern areas and Scotland. Pinch out the top of cordon tomatoes when appropriate, maintain modest watering and let the existing crop mature. Harvest fruits as they colour and remove damaged leaves with clean secateurs. At season's end, compost healthy residues and refresh beds or containers with garden compost before the next crop. Keeping a note of planting date, fruit set and feeding response will help you tune the schedule to your own garden.
Frequently asked questions
When should I start feeding tomato plants?
Begin a high-potash liquid feed once the first fruits have set, not simply when the first flowers open. Before then, well-prepared soil or fresh peat-free compost usually provides enough nutrition. Starting too early can encourage leafy growth at the expense of fruit production.
Can I feed tomatoes in dry compost?
It is better to water first. Dry compost may shed the liquid or take it up unevenly, stressing roots. Once the root area is evenly moist, apply a correctly diluted feed according to its guidance. Regular watering is as important as the feed itself.
Why are my tomato plants leafy but not fruiting well?
Early or excessive feeding, especially alongside rich soil, can encourage foliage rather than fruit. Check that plants have sufficient light, appropriate spacing and pollination conditions. For cordon types, remove sideshoots regularly. Once fruit sets, use a high-potash feed at the recommended interval rather than increasing it.
General guidance for UK home gardens and allotments. Conditions vary by region, soil and season; the RHS or a local garden centre can give site-specific advice. Page updated 18 Sep 2026.