Temperature decides which fruit you can grow more than any other single factor. A fig that thrives in a warm climate will die in a cold one, an apple that needs a cold winter will not fruit in a warm one, and a peach blossom that opens too early will be killed by a single late frost. Fruit growing is, at its heart, matching the temperature needs of the plant to the temperatures your garden actually gets — and that match is made at planting time, when you choose the variety, not later, when you are trying to save a tree that was never suited to your climate.
There are three temperature questions for every fruit: how much cold it needs in winter, how much cold it can survive, and how much heat it needs in summer. The first is chill hours — the hours of winter cold a tree needs before it will flower and fruit properly. The second is hardiness — the lowest winter temperature the tree can survive. The third is heat — the warmth a fruit needs to ripen, which is why figs and melons struggle in a cool summer even when they survive the winter.
Your USDA hardiness zone tells you the second of these — the coldest temperature your garden usually gets — and it is the starting point for every fruit decision. But the zone alone is not enough: two gardens in the same zone can have very different chill hours, very different spring frosts and very different summers, and the local differences matter as much as the zone. If you are unsure about a variety, a spray, or a diagnosis, check your local extension service — its advice is matched to your climate and soil.
Chill hours: the winter cold fruit needs to fruit
Chill hours are the hours a fruit tree spends below a cool threshold during winter, and they are the tree's way of knowing winter has happened. Apples, pears, plums, cherries, peaches and currants all need a certain number of chill hours before they will flower and fruit properly in spring. If the winter is too warm and the tree does not get its chill, it flowers late, unevenly or not at all, and the fruit set is poor. The number varies by variety: some apples need many hundreds of chill hours and suit only cold winters, while low-chill varieties of apples, peaches and plums need far fewer and will fruit in warm zones where a high-chill variety would fail. Figs, citrus, grapes and strawberries need little or no chill, which is why they suit warm climates. If you garden in a warm zone, choose low-chill varieties — your nursery and your extension service can tell you which ones fruit reliably where you live — and do not plant a high-chill variety in the hope that a cold snap will be enough. Our growing guides for apples and peaches cover the chill needs of the common fruits.
Hardiness: surviving the winter
Hardiness is the coldest temperature a plant can survive, and it is what the USDA zone system measures. Apples, pears, plums and currants are among the hardiest fruit, surviving cold winters that would kill a peach or a fig. Peaches and sweet cherries are less hardy and are damaged by severe cold, especially when the wood has not hardened properly in autumn. Figs are hardy only in mild climates, and in a cold climate they must be grown against a warm wall or in a container that can be sheltered. Citrus is the least hardy fruit of all: most citrus is damaged by even a light frost, and it is grown outdoors only in frost-free climates, or indoors elsewhere. A tree's hardiness is not fixed: a young tree is less hardy than an established one, a tree that was fed late in the season is less hardy because its growth has not hardened, and a tree that is drought-stressed going into winter is less hardy than one that was watered. The hardiness zone finder can tell you your zone, and your planting calendar shows what grows in it.
Spring frost and the blossom: the most dangerous moment
The most dangerous temperature moment in the fruit year is not the depths of winter but a late spring frost, when the blossom is open and a single night below freezing can destroy the whole crop. Apple and pear blossom is damaged by a hard frost, peach and plum blossom is more tender still, and a frost after a warm spell is worse than a frost in a cold spring, because the blossom has already opened. The defence is site and timing: do not plant fruit in a frost pocket — a low spot where cold air collects — and plant on a slope or a raised spot where cold air drains away. Choose late-flowering varieties if late frosts are common where you live. And on a frosty night, cover a small tree or bush with horticultural fleece, which can save the blossom, or run a sprinkler — the water freezing on the blossom releases heat and protects it, though this is a technique for orchards rather than a single tree. A tree that loses its blossom to frost will usually flower again next year, but the crop for this year is gone, so prevention is worth the effort.
Summer heat: ripening figs, melons and grapes
Heat is what ripens fruit, and in a cool summer the fruit that needs heat will struggle. Figs need a long, hot summer to ripen, and in a cool climate they are best grown against a south-facing wall, where the stored heat helps them. Melons need warmth from sowing to harvest, and in a cool climate they are best grown in a greenhouse or under a cloche. Grapes need sun and warmth on the bunches to sweeten, and in a cool climate they should be grown on a south-facing wall or in a greenhouse. Citrus needs warmth to ripen and to grow, and it stops growing when the temperature drops, which is why it is an indoor plant in cool climates. But heat can also be too much: in a very hot climate, fruit can scorch, leaves can burn, and the plant can shut down in the hottest part of the day. Mulch, water and a little afternoon shade are the answers, and in a hot climate, the morning sun matters more than the afternoon sun.
Protecting fruit from cold and heat
For cold, the protections are site, variety, mulch and cover. Plant in a sheltered spot out of the wind, choose a variety hardy for your zone, mulch the roots in autumn to insulate them, and cover a small tree or bush with fleece on a frosty night. For a young tree, wrap the trunk in winter to prevent sunscald, and paint it with whitewash. For container fruit, move the pot to a sheltered wall or indoors before the first frost, and wrap the pot so the roots do not freeze. For heat, the protections are mulch, water and shade: a thick mulch keeps the soil cool, deep watering keeps the plant hydrated, and a shade cloth or a taller plant to the west gives the fruit a break from the hottest sun. A greenhouse or a polytunnel extends the season at both ends, giving tender fruit the warmth it needs in spring and autumn, and it is the best investment a fruit grower in a cool climate can make for figs, melons, grapes and citrus.
Matching fruit to your climate
The surest way to grow fruit successfully is to grow the fruit that suits your climate, rather than fighting it. In a cold climate, grow apples, pears, plums, currants, gooseberries, raspberries and strawberries, and choose hardy, late-flowering varieties. In a mild climate, add peaches, cherries, figs and grapes, and grow them against a warm wall. In a warm climate, grow citrus, figs, grapes, melons and low-chill peaches and plums, and give them water and a little afternoon shade. In a hot climate, grow citrus, figs and grapes, and protect them from the fiercest sun. Your neighbours' gardens are the best guide: the fruit that fruits well in the gardens around you is the fruit that suits your climate, and the fruit that nobody grows is usually the fruit that does not. Ask your nursery and your extension service, and let the local knowledge guide you.
Frequently asked questions
What are chill hours?
Chill hours are the hours of winter cold a fruit tree needs before it will flower and fruit properly in spring. Apples, pears, plums and cherries need them; figs, citrus and grapes need little or none.
Why did my apple tree not flower this year?
If you garden in a warm climate, the tree may not have had enough chill hours. Choose a low-chill variety suited to your zone, and ask your extension service which varieties fruit reliably where you live.
How do I protect fruit blossom from frost?
Plant on a slope where cold air drains away, avoid frost pockets, choose late-flowering varieties, and cover a small tree or bush with horticultural fleece on a frosty night.
Can I grow figs in a cold climate?
Only against a warm, south-facing wall, or in a container that can be sheltered in winter. Figs need a long, hot summer to ripen and are damaged by severe cold.
What temperature kills citrus?
Most citrus is damaged by even a light frost. It is grown outdoors only in frost-free climates, and indoors or in a greenhouse elsewhere.
Temperature is the frame within which all fruit growing happens: chill in winter, hardiness through the cold, protection for the blossom, and heat for the ripening. Match the fruit to your climate, protect the blossom, and let the wall and the mulch do their work. For the temperature needs of individual fruits, see the growing guides, and find your zone with the hardiness zone finder.