Summer heat is the defining challenge of the season, and in a hot summer it is the difference between a garden that thrives and a garden that merely survives. Heat dries the soil, wilts leaves, scorches fruit, bolts lettuce, splits tomatoes and stresses every plant in the garden, and a heatwave — several days of extreme heat in a row — can do in a week what a whole season of neglect cannot. The answer is not a single trick but a combination: shade where it is needed, deep water at the right time, mulch everywhere, and a gardener who knows the signs of heat stress and acts on them early. This guide covers protecting plants, lawns, containers and fruit from summer heat, in general terms that apply across zones, with the reminder to check your local extension service for local conditions and any watering restrictions.
Recognising heat stress
Heat stress shows itself in the leaves first. A plant wilting in the middle of a hot afternoon is not necessarily in trouble — many plants wilt in the heat to reduce water loss and recover in the evening — but a plant that is still wilted in the evening needs water, and a plant that is wilted every morning has a deeper problem. Scorched leaves, with brown, papery patches on the side facing the sun, are a sign of too much direct sun, and they will not recover — the damaged leaf should be removed so you can see new growth clearly. Leaf drop, small fruit, fruit that drops early, and lettuce or herbs running to seed are all signs of heat stress, and they are all worse when the plant is also short of water.
Fruit shows heat stress too: tomatoes develop sunscald, a pale, papery patch on the side facing the sun, and they split when watering is irregular; peppers and eggplant drop their flowers in extreme heat; and berries dry out on the bush if they are not watered. The signs are the same across crops, and the response is the same too — shade, water and mulch — applied early, before the damage becomes severe. For the seasonal context, see the zone page for Zone 5 summer gardening and our summer watering guide.
Shade: the most effective protection
Shade cloth is the most useful heat protection a gardener can own. Draped over hoops or stakes above a bed, it cuts the sun's intensity without blocking air flow, and it can reduce the temperature underneath by several degrees — often enough to make the difference between a plant that copes and one that does not. Use it over lettuce, spinach, peas, brassicas and other cool-season crops, over newly planted transplants, and over any bed that is struggling in a heatwave. A light-coloured shade cloth reflects heat better than a dark one, and it should be put up before the heat arrives, not after the plants have already wilted.
Temporary shade works too: a sheet, a piece of old net curtain, or a cardboard box propped over a row will protect seedlings for a day or two, and moving containers into light shade for the hottest part of the day is the simplest protection of all. Planting tall crops, such as sweet corn or sunflowers, on the sunny side of a bed will shade shorter crops in the afternoon, and a trellis covered with beans or squash does the same job while also producing food. Shade should be filtered light, not darkness — plants still need light to grow, just not the full force of midday sun on the hottest days. The sunlight calculator can help you check how much sun a spot receives.
Watering in extreme heat
In extreme heat, water deeply and in the morning, so the soil is moist before the heat builds and the water has time to soak down to the roots. A thorough watering that wets the soil to spade depth is worth far more than a light sprinkle, which evaporates before it reaches the roots and teaches plants to depend on daily watering. Water at the base, not over the foliage, and use a soaker hose or drip irrigation where you can, so the water goes to the roots and not onto paths and fences. In a heatwave, check containers twice a day, because a pot in full sun can dry out completely between morning and afternoon.
Mulch is what makes watering work in extreme heat: a layer of straw, compost or wood chips over the soil keeps it cooler, slows evaporation, and stops the surface baking into a crust that water cannot penetrate. Water before you mulch a dry bed, so you are locking moisture in, and top up mulch where it has thinned. In a heatwave, prioritise water for newly planted trees, vegetables and containers, which have the least reserves, and let established trees, shrubs and lawns cope with less — a lawn that goes brown in a drought is usually dormant, not dead, and it will green up when rain returns. The mulch calculator can help with quantities, and our summer mulching guide covers mulch in detail.
Protecting vegetables, fruit and flowers
Leafy crops are the most heat-sensitive plants in a summer garden: lettuce, spinach, peas and herbs such as basil and cilantro wilt fast, bolt quickly, and cannot be brought back once they have run to seed. Shade them first, keep them well watered, and sow them where they get afternoon shade. Tomatoes, peppers and cucumbers need steady water to avoid splitting, blossom end rot and bitter fruit, and they benefit from a mulch that keeps the soil evenly moist. For crop detail, see growing tomatoes and growing lettuce, and our summer vegetable care guide.
Fruit trees and bushes need deep watering in a heatwave, especially young trees and any tree carrying a heavy crop, and a mulch ring around the base will hold the moisture in. Pick fruit in the morning, before the heat builds, and bring it indoors promptly, because fruit left in the sun will spoil quickly. Flowers in beds need watering at the base, and containers need checking daily; deadhead regularly, because a plant that is allowed to set seed in the heat will stop flowering. Our summer fruit care and summer flower care guides cover the seasonal care.
Lawns, containers and houseplants in heat
A lawn in extreme heat should be mown high and infrequently, because longer grass shades the soil and grows deeper roots, and it should be watered deeply once a week or allowed to go dormant — a brown lawn in a drought is usually dormant, not dead. Keep off the lawn as much as you can in a heatwave, because wear on dry grass is worse than wear on moist grass, and do not feed a drought-stressed lawn. Our summer lawn care guide covers the lawn routine in full.
Containers need the most attention in a heatwave: group pots together so they shade each other's sides, mulch the surface of the compost, stand pots on a tray of damp gravel, and water twice a day if needed. Houseplants moved outdoors should be in light shade, not full sun, and tropical plants should be brought in if a heatwave is followed by a cold night. Indoors, move houseplants away from hot windowsills, raise humidity by grouping plants together, and check them daily for water. Our summer houseplant care guide covers the indoor routine.
After a heatwave
After a heatwave, check plants in the evening, when they have had a chance to recover. A plant that has perked up by evening was stressed but not damaged; a plant that is still wilted needs water. Remove scorched leaves so you can see new growth, hold off feeding a stressed plant until it is growing again, and water deeply and mulch any beds that dried out. Note which beds and pots suffered most, because that tells you where to add shade, mulch or water before the next heatwave — and in many areas, heatwaves are becoming more frequent, so the habits you build now will matter more every year.
If a heatwave is forecast, prepare before it arrives: put up shade cloth, mulch bare soil, water deeply, move containers into shade, and fill watering cans and rain butts so you are ready. A garden prepared before the heat is a garden that copes with it, while a garden left to face a heatwave unprepared will struggle. For the spring version of this advice, see our spring heat protection guide, and browse the guides hub and the planting calendar for the full seasonal series.
Frequently asked questions
How do I protect plants from extreme summer heat?
Put up shade cloth over beds before the heat arrives, water deeply in the morning at the base of plants, and mulch bare soil to keep it cool and moist. Move containers into light shade for the hottest part of the day, and check them twice a day in a heatwave.
What are the signs of heat stress in plants?
Wilting that persists into the evening, scorched leaves with brown papery patches, leaf drop, small or dropping fruit, and lettuce or herbs running to seed. A plant that wilts in the afternoon but recovers by evening is coping; one still wilted in the evening needs water.
Should I water plants in the middle of a hot day?
It is better to water deeply in the early morning, but a plant wilting badly in the afternoon should be watered at the base whenever you notice it — a wilted plant needs water more than it needs to wait for the ideal time.
Will my lawn die in a heatwave?
Usually not — most lawn grasses go dormant in drought and green up again when rain returns, even after several weeks of brown. Mow high and infrequently, keep off the lawn, water deeply once a week or let it rest, and do not feed a drought-stressed lawn.
How do I protect containers in a heatwave?
Group pots together so they shade each other, mulch the surface of the compost, stand them on a tray of damp gravel, and water twice a day if needed. Move them into light shade for the hottest part of the day.