What plants are frost resistant?

Frost resistant plants hold their tissue together below freezing because their cells tolerate or resist ice forming inside them. Kale, spinach, garlic, leeks, and many alliums shrug off light frost and keep growing into the cold. The rating on the tag tells you the lowest temperature that plant survives, so read it against the low your own yard reaches.

What plants survive winter outside?

Plants survive winter outside when their rated low sits below the coldest night your ground reaches. Garlic, hardy onions, and established perennials rated well under your winter low come through in the open. Check your real low first, since a plant rated to your area's average low can still die in a pocket that drains colder.

What plants grow in winter?

Cold-hardy leafy crops keep growing through winter as long as soil temperature and daylight allow, and their tissue tolerates frost. Spinach, mâche, and some lettuces hold in a bed that stays above their rated low, and a cold frame raises that bed's night temperature. In our garden we direct-seeded lettuce and spinach in late July for cold-season harvest.

How do I protect plants in winter if they're only partly hardy?

Cover a partly hardy plant on the nights its rated low is breached, since frost cloth traps ground heat and buys a few degrees. Move containers against a wall or into a cold frame, and mulch roots to slow the soil's heat loss. The cover works only on the nights your yard dips below the plant's threshold, so knowing that low is what tells you when to act.

August 13, 2026 · Updated September 12, 2026

How frost resistant plants read against your real low

A plant labeled frost resistant carries a temperature, and the label helps only once you know your yard drops below it. A tag that reads hardy to −5°C promises the plant survives down to −5°C. Whether your ground reaches −5°C is a separate question, and the forecast for your area won't answer it for your yard.

What a frost tolerance rating means

A frost tolerance rating names the lowest temperature the plant's tissue survives before ice forms inside its cells and ruptures the walls. Above that number the cells hold and the plant keeps its structure. Below it, the water inside freezes, expands, and the leaf collapses into mush. The rating comes as a stated low in degrees or as a hardiness zone, which is a band of average annual minimum temperatures.

So frost resistant and fully hardy describe two points on the same scale. A frost resistant crop like lettuce tolerates a light touch of frost and stops there. Garlic and hardy alliums sit far lower and overwinter in open ground. Both numbers describe the plant. Neither number describes your night.

Why the rating is only half the answer

The other half is your real low, and that number lives in your yard. A forecast low describes a wide area, and a published frost date leans on a weather station that can sit miles away. Dense cold air sinks. On a still, clear night it slides downhill and pools in the lowest ground it can reach. A bed at the foot of a slope can sit several degrees under the forecast, and a bed against a sunlit wall holds warmer.

In our own garden our station runs about 7°F under the forecast when the night turns cold. That gap moves the calendar too. Our published last spring frost is April 28, but after the learned offset our effective last frost lands on May 20. Our coldest night this year hit 3°F. A plant rated to 10°F would have died in the open here, even though its number looked safe against a milder forecast.

This is the same reason a published frost date misleads. We cover it in your last frost date is probably wrong.

How to find your real low

You have two ways to turn the forecast into your yard's number. The first is a manual offset. Watch your own thermometer against the forecast across a few cold nights, note how much colder your ground runs, and subtract that from every forecast low. Siltwell stores that manual offset and adjusts your frost alerts by it.

The second is a connected station that learns the offset for you. It logs its own readings next to the forecast and averages the difference night after night. After about 14 overlapping days it locks in that learned bias, so the offset rests on real data. Once it holds, frost alerts arrive already adjusted to your station.

If you don't have a station yet, the microclimate checker reads recent cold nights from home stations near you and works out how far the forecast tends to sit above your area's true low. That estimate covers the ground around your yard. Confirm it with your own thermometer over a few nights before you trust it.

A rating names a temperature. It does not tell you how long the cold lasts, how wet the soil sits around the roots, or how hard the wind blows, and all three change whether a plant near its limit survives the night.

Matching plants to your low

Once you have your real low, matching plants is direct. Pick anything rated below the coldest night your yard hits and it lives in the open. For crops rated near your low, plan to protect them on the nights the forecast, minus your offset, crosses their number.

Well below your low. Garlic, hardy onions, and established cold-hardy perennials overwinter unprotected.
Near your low. Spinach, kale, and mâche hold through frost and grow on mild days, and a cold frame lifts their bed a few degrees on the coldest nights.
Above your low. Tender crops need a cover on the breaching nights, or they come indoors.

For what keeps producing through the cold season and how a warm pocket extends it, see plants that grow in winter and plants that survive winter outside.

Start tonight by logging your yard's low against the forecast, or connect a station and let it learn the gap. Once you know how cold your ground gets, every frost rating on every tag turns into a plain yes or no for your beds.

Common questions.

What plants are frost resistant?: Frost resistant plants hold their tissue together below freezing because their cells tolerate or resist ice forming inside them. Kale, spinach, garlic, leeks, and many alliums shrug off light frost and keep growing into the cold. The rating on the tag tells you the lowest temperature that plant survives, so read it against the low your own yard reaches.
What plants survive winter outside?: Plants survive winter outside when their rated low sits below the coldest night your ground reaches. Garlic, hardy onions, and established perennials rated well under your winter low come through in the open. Check your real low first, since a plant rated to your area's average low can still die in a pocket that drains colder.
What plants grow in winter?: Cold-hardy leafy crops keep growing through winter as long as soil temperature and daylight allow, and their tissue tolerates frost. Spinach, mâche, and some lettuces hold in a bed that stays above their rated low, and a cold frame raises that bed's night temperature. In our garden we direct-seeded lettuce and spinach in late July for cold-season harvest.
How do I protect plants in winter if they're only partly hardy?: Cover a partly hardy plant on the nights its rated low is breached, since frost cloth traps ground heat and buys a few degrees. Move containers against a wall or into a cold frame, and mulch roots to slow the soil's heat loss. The cover works only on the nights your yard dips below the plant's threshold, so knowing that low is what tells you when to act.

Related guides

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