What plants are frost resistant?

Frost resistance is really a spectrum of rated tolerances, not a yes/no label. Hardy perennials like kale, leeks, garlic, hellebores, and many alliums shrug off hard freezes, while "half-hardy" plants tolerate a light touch of frost but die in a real freeze. The rating only tells you what a plant can survive — it's useful only once you know how cold your specific yard actually gets.

What plants survive winter outside?

Fully hardy plants rated below your yard's coldest night survive outdoors without protection — think garlic, kale, spinach, leeks, many ornamental grasses, and established woody perennials. The safe move is to compare a plant's rated low to the actual low your site tends to hit, since a sheltered yard can run several degrees warmer or colder than the regional forecast. That gap is the difference between a plant coasting through and quietly dying.

What plants grow in winter?

Cold-season crops that keep growing (slowly) in winter include kale, spinach, mâche, claytonia, leeks, and overwintering garlic and onions. Growth stalls once daylight drops below about ten hours, so most "winter" plants are really holding rather than growing until spring. Whether they hold outside or need cover depends on how cold your yard actually gets — not the calendar.

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

Row cover, cloches, a cold frame, and heavy mulch each buy you a few degrees, which is often enough to bridge the gap between a plant's rated low and a hard night. The key is knowing which nights actually threaten your yard so you cover before the freeze, not after. A frost alert calibrated to your own site — or at least the regional forecast checked against how cold your area runs — tells you when to bother.

August 13, 2026

"Frost Resistant" Is a Number — and It Only Helps If You Know How Cold Your Yard Really Gets

Search "frost resistant plants" and you get list after list ranking plants by a hardiness zone or a frost-tolerance rating: this one's good to −5°C, that one shrugs off a hard freeze, this one dies at the first white morning. All true, all useless on their own — because a plant rated to −5°C is only safe if you know your yard actually bottoms out warmer than −5°C. The rating is half the equation. Your real local low is the half every list leaves out.

A frost rating is a number waiting for a second number

"Frost resistant" isn't a switch, it's a temperature. Fully hardy plants like kale, leeks, and garlic keep their feet in the ground through hard freezes. "Half-hardy" plants — many salad greens, young brassicas, a lot of herbs — tolerate a light touch of frost and then quit when it gets serious. The rating tells you the plant's floor. What it can't tell you is whether your garden ever hits that floor.

That's the trap. The forecast low you see is measured at an airport or a regional station, often over open, exposed ground. Your yard is not that spot. A fenced, south-facing bed against a warm wall can run several degrees milder than the number on your phone; a low pocket where cold air pools can run several degrees colder. So a plant rated to −5°C might sail through in one corner of your garden and die ten feet away in a frost hollow — on the exact same night.

Read the rating against your real low, not the airport's

The honest way to use a hardiness rating is to line it up against the temperature your specific spot actually reaches. That means finding out how your yard deviates from the regional forecast — its bias. Once you know your beds run, say, 2°C colder than the forecast on still nights, a plant rated to −4°C is only truly safe when the forecast low stays above about −2°C.

You can start narrowing this without buying anything. Siltwell's public microclimate checker compares the forecast low to what nearby home weather stations actually recorded over all recent nights, and reports how much colder or warmer your area tends to run — along with how many stations it's drawing on and a confidence level. It's an area indicator, not a guaranteed reading for your particular bed, but it's a far better starting point than assuming the airport number applies to your fence line.

A connected station learns your yard's own bias

The area figure gets you close. Your own yard gets you closer. If you connect a home weather station to Siltwell, it starts comparing your station's readings to the Open-Meteo forecast and averaging the difference — station minus forecast — over time. A colder-than-forecast site shows up as a negative bias.

Here's the honest part: that learned offset isn't trusted instantly. Siltwell waits for about 14 overlapping station-and-forecast days before it treats your bias as reliable enough to fold into frost alerts. Before that threshold, it's still gathering evidence. After it, your frost warnings arrive adjusted to your station — the alert literally reads "adjusted to your station" — instead of parroting the regional forecast. That's the difference between being told "it might frost somewhere in the region" and "the adjusted low for your yard is going to clip your half-hardy plants tomorrow night."

No station? The free tier still lets you enter a manual temperature offset in Settings if you already know your yard runs a couple of degrees cold — those alerts read "adjusted for your site." It's a blunter tool than a learned bias, but it beats trusting the airport.

What to actually plant — and where

Once you know your real low, the plant lists finally become useful. Sort by rated tolerance against your number:

Rated well below your coldest night: fully hardy stuff — kale, leeks, garlic, spinach, mâche, hellebores, established perennials. Plant and forget.
Rated near your low: the risky middle. Half-hardy greens and young brassicas that survive a light frost. Put them in your warmest microclimate — against a wall, out of the frost pocket — and keep row cover handy.
Rated above your low: tender plants that need protection or a move indoors. A rating like this in an exposed bed is a countdown, not a plan.

The same logic reframes what "grows in winter" even means. Most cold-season crops don't really grow once daylight drops below about ten hours — they hold. Whether they hold outside or need a cloche comes straight back to your real low. If you want to build a whole cold-season plan around your specific spot, the winter-plant microclimate guide goes deeper, and if you've never questioned the dates you plant by, your last frost date is probably wrong is the companion piece.

Station-calibrated frost alerts and connecting a station are part of Siltwell Pro ($22/year, with a 14-day free trial); the free tier lets you enter a manual site offset by hand and still gives forecast-based guidance. Siltwell works with Ecowitt, Ambient, Tempest, and Davis stations — here's how to connect one and let it learn your yard's bias.

One honest caveat: knowing your real low narrows the guesswork, it doesn't repeal the weather. A learned bias is an average — an unusual night, a sudden radiative freeze, or a spot the wind funnels through can still beat the number. Use your calibrated low to sort plants and to know which nights to cover; then trust your eyes and a length of row cover for the rest. Fewer bad bets is the goal, not blind faith in a rating.

Common questions

What plants are frost resistant?: Frost resistance is really a spectrum of rated tolerances, not a yes/no label. Hardy perennials like kale, leeks, garlic, hellebores, and many alliums shrug off hard freezes, while "half-hardy" plants tolerate a light touch of frost but die in a real freeze. The rating only tells you what a plant can survive — it's useful only once you know how cold your specific yard actually gets.
What plants survive winter outside?: Fully hardy plants rated below your yard's coldest night survive outdoors without protection — think garlic, kale, spinach, leeks, many ornamental grasses, and established woody perennials. The safe move is to compare a plant's rated low to the actual low your site tends to hit, since a sheltered yard can run several degrees warmer or colder than the regional forecast. That gap is the difference between a plant coasting through and quietly dying.
What plants grow in winter?: Cold-season crops that keep growing (slowly) in winter include kale, spinach, mâche, claytonia, leeks, and overwintering garlic and onions. Growth stalls once daylight drops below about ten hours, so most "winter" plants are really holding rather than growing until spring. Whether they hold outside or need cover depends on how cold your yard actually gets — not the calendar.
How do I protect plants in winter if they're only partly hardy?: Row cover, cloches, a cold frame, and heavy mulch each buy you a few degrees, which is often enough to bridge the gap between a plant's rated low and a hard night. The key is knowing which nights actually threaten your yard so you cover before the freeze, not after. A frost alert calibrated to your own site — or at least the regional forecast checked against how cold your area runs — tells you when to bother.

Related guides

Free planting tools

When to plant — the last date to sow each crop before your fall frost
Microclimate checker — how much colder your yard runs than the forecast
GDD estimator — whether a crop will ripen where you are