Summer is the season when plants are growing fastest and using the most nutrients, and it is also the season when feeding can do the most harm if it is done badly. A plant fed at the wrong time, at too high a strength, or on dry soil can have its roots burned, push out soft growth that pests love, or simply waste the fertiliser as it washes away in the next watering. The aim of summer feeding is steady, gentle nutrition that supports growth without forcing it — mostly through compost, mulch and light liquid feeds, applied to moist soil in the cool of the day. This guide covers what to feed in summer, what to leave alone, and how to tell whether a plant actually needs feeding at all. For local advice, check your local extension service.
Does your garden need feeding in summer?
Before you feed anything, ask whether it needs it. A plant growing steadily, with healthy green leaves and a good crop of flowers or fruit, is already getting what it needs, and feeding it will not make it grow better — it may make it grow worse, by pushing soft, leafy growth at the expense of flowers and fruit. The plants that genuinely need summer feeding are the heavy feeders in active growth: tomatoes, squash, cucumbers, sweet corn and roses, container plants whose small volume of compost is quickly exhausted, and any plant that is pale, slow-growing or producing small fruit despite adequate water and light.
Soil testing is the reliable way to know what is missing, and a basic test will tell you the pH and the main nutrients. If you have never tested your soil, summer is a reasonable time to do it, though the results are most useful when they guide your feeding and composting over the following season rather than prompting an immediate heavy feed. Remember that compost and mulch feed the soil slowly and steadily, and for most beds they are a better investment than any bagged fertiliser. The fertiliser calculator can help you work out quantities when you do decide to feed.
Liquid feeds: the summer workhorse
Liquid feeds are the most useful form of feeding in summer, because they act quickly, can be applied at a controlled strength, and can be given with watering so they reach the roots evenly. Use a balanced liquid feed, or one made for the crop — a tomato feed high in potash for tomatoes, peppers and cucumbers once they are flowering and fruiting, for example — and always use it at half the strength on the label for the first application, increasing only if the plant responds well. Apply in the evening or early morning, on soil that is already moist, and never on dry soil, because a strong feed on dry roots can burn them.
Compost tea, made by steeping well-rotted compost in water, is a gentle alternative that feeds the soil as well as the plant, and it is a good use for compost that is not yet fully broken down. Seaweed-based feeds are also gentle and are useful as a general tonic for plants under stress, though they are low in the main nutrients and should not be relied on as the only feed for heavy crops. Whatever you use, feed little and often through the season rather than giving one heavy dose — a small feed every two weeks is safer and more effective than a large feed once a month.
Compost and mulch as summer feeding
The best summer feeding is often not a fertiliser at all but a mulch of compost. A layer of well-rotted compost around vegetables, fruit bushes and roses feeds the soil slowly as worms work it in, holds moisture, keeps roots cool, and improves the soil for the following season. Apply it after watering, keep it clear of stems, and top it up where it has thinned. In a hot summer, compost mulch is doing three jobs at once — feeding, watering and cooling — and no bagged product does all three.
Green manures and cover crops sown on empty beds in summer feed the soil for the next season, fixing nitrogen or adding organic matter that is dug in later. If a bed is empty in midsummer, sowing a quick green manure is a better use for it than leaving it bare, and it will be ready to dig in before the autumn planting. The compost ratio calculator can help you keep a compost heap producing well through the summer, when it needs watering and turning more often than in cooler weather.
Feeding vegetables, fruit and flowers
Vegetables are the heaviest feeders in summer. Tomatoes, peppers, cucumbers, squash and sweet corn all benefit from a regular liquid feed once they are flowering and fruiting, and leafy crops such as lettuce and chard need nitrogen to keep producing leaves — though too much nitrogen on lettuce makes it soft and prone to pests. Root crops such as carrots, parsnips and beetroot need very little feeding, and too much nitrogen makes them grow leaves at the expense of roots, so feed them lightly or not at all. For crop detail, see growing tomatoes and growing cucumbers, and our summer vegetable care guide.
Fruit trees and bushes need little feeding in summer if they were mulched with compost in spring, and heavy feeding now pushes soft growth that aphids love. Strawberries benefit from a feed after they have finished fruiting, to help them build strength for next year, and container fruit such as blueberries in pots need regular light feeding because their compost is quickly exhausted. Flowers in beds need less feeding than flowers in containers; roses and dahlias are the exceptions, and both respond well to a regular liquid feed through the flowering season. Our summer fruit care and summer flower care guides cover the seasonal detail.
Containers and houseplants in summer
Container plants need feeding more than any other plants in summer, because their small volume of compost holds only a few weeks' worth of nutrients and they are watered frequently, which washes nutrients away. Feed containers every one to two weeks with a liquid feed at half strength, and water first so the feed is applied to moist compost. Hanging baskets dry out and exhaust their compost fastest of all, and they may need feeding weekly in hot weather. If a container plant is pale and slow despite regular feeding, it may need repotting into fresh compost rather than more fertiliser.
Houseplants that spent the summer outdoors also need regular feeding while they are growing, at the same half-strength, every-two-to-four-weeks rhythm as in spring, and they should not be fed once growth slows in autumn. A plant that has just been repotted does not need feeding for a few weeks, because fresh compost already contains nutrients. See our summer houseplant care guide for the full routine, and the fertiliser calculator for quantities.
What not to feed, and common mistakes
Do not feed a plant that is stressed by drought, heat or transplanting — water it first, let it recover, and feed it only when it is growing again. Do not feed in the heat of the day, on dry soil, or at full strength on a plant that has never been fed before. Do not feed newly planted trees and shrubs heavily in their first summer; they need to establish roots, not to be pushed into top growth they cannot support. And do not feed lawns heavily in a hot, dry summer — a stressed lawn fed with nitrogen will burn, and the best summer lawn care is usually watering deeply and mowing high, as our summer lawn care guide explains.
The most common feeding mistake in summer is treating fertiliser as a cure for every problem. Yellow leaves can mean overwatering, underwatering, too little light, or a plant that is simply at the end of its season, and none of those are fixed by feeding. Look at water and light first, and feed only when the plant is otherwise healthy but clearly short of nutrients. A garden fed thoughtfully — compost first, liquid feeds little and often, and nothing at all for plants that do not need it — will be healthier than one fed heavily on a schedule.
Frequently asked questions
How often should I fertilize in summer?
Little and often is the rule: a liquid feed at half strength every one to two weeks for heavy feeders such as tomatoes and container plants, and every two to four weeks for most other plants. Compost mulch feeds slowly all season and is the best base for most beds.
Can fertilizer burn plants in summer?
Yes — a strong feed applied to dry soil in hot weather can burn roots, and feeding a drought-stressed plant makes the damage worse. Always water first, feed in the cool of the morning or evening, and use half the label strength for the first application.
What should I feed tomatoes in summer?
Once tomatoes are flowering and fruiting, use a liquid feed high in potash, such as a tomato feed, every one to two weeks at the label strength or weaker, on moist soil. Compost mulch around the base helps too, and overfeeding with nitrogen produces leaves at the expense of fruit.
Do I need to feed container plants in summer?
Yes — containers exhaust their compost quickly and are watered often, which washes nutrients away. Feed every one to two weeks with a liquid feed at half strength, on moist compost, and consider repotting into fresh compost if a plant stays pale despite feeding.
Should I fertilize my lawn in summer?
Usually not heavily in a hot, dry summer — nitrogen on a stressed lawn can burn it. Water deeply and rarely, mow high, and save heavy feeding for cooler weather in spring or autumn. Check your local extension service for lawn advice in your area.