July 31, 2026

Which Plants Grow in Winter Depends on How Cold Your Yard Actually Gets

Search "plants that grow in winter" and you get the same list every time: kale, spinach, leeks, garlic, broad beans. It's a fine list. What none of them mention is that two gardens a mile apart can hit wildly different overnight lows — a low, still pocket can sit several degrees colder than the number on the regional forecast. The plant that overwinters happily on one street gets flattened on the next. The real question isn't which winter crops exist; it's which ones survive your cold.

The standard list is right — and blind to your yard

There's nothing wrong with the usual roster. Kale, leeks, spinach, corn salad (mâche), garlic, and overwintering broad beans genuinely tolerate frost, and several — parsnips and kale especially — turn sweeter after a cold snap converts starch to sugar. If you want a safe starting point, that list is it.

The trouble is that "frost tolerant" is a spectrum, not a switch. Spinach shrugging off a light −2°C frost is a different proposition from surviving a −7°C freeze in a hollow where cold air pools. A generic list can't tell you which end of that spectrum your garden lives at, because it's written for a whole climate zone — and your zone map doesn't know about the slope, the fence, or the frost pocket at the bottom of your plot.

Why "how cold" is a per-yard question

Cold isn't distributed evenly across a neighbourhood. On a clear, still night, cold air drains downhill and settles in low spots, so the bottom of a garden can be several degrees colder than the top. A wall that holds the day's heat, an open sky with no cloud blanket, a dip that traps air — all of these push your real overnight low away from the regional forecast, sometimes by a lot.

That gap is exactly what decides whether your winter greens live. If your yard runs consistently colder than the forecast, the "hardy to zone X" label on a seed packet is optimistic for you specifically. If it runs milder — say you garden against a south-facing brick wall in a town centre — you can push crops the list would call risky. Either way, the useful number is your deviation from the area forecast, and that's not something a listicle can supply.

Check how cold your area actually runs — before you plant

You don't need to guess, and you don't need to buy hardware to start. Siltwell's public microclimate checker compares the forecast low to what nearby home weather stations actually recorded over recent nights, then reports how much colder or warmer your area tends to run — with a count of how many stations it used and a confidence level so you know how much to trust it.

One honest boundary up front: this is an area indicator, not a guaranteed reading for your exact bed. It tells you whether your neighbourhood tends to run, say, a couple of degrees below the forecast — useful for choosing crops — but it can't see the private frost pocket at the bottom of your garden. For that, you need a sensor in your own ground.

From "how cold" to what you actually plant

Turn the number into decisions. Think of it as three broad cases:

• Your area runs colder than the forecast. Lean hard into the toughest crops — kale, leeks, parsnips, garlic — and plan on cover for anything more tender. Treat the seed-packet hardiness rating as a best case, not a promise.
• Your area runs about the same. The standard list is a fair guide. Plant it, watch how the first frosts land, and adjust next season.
• Your area runs milder. You have room to push — winter salad crops, overwintering onions, and hardier herbs that a colder plot couldn't carry. A warm wall is a genuine asset here.

This is where knowing your real cold earns its keep: it moves you off a one-size list and onto choices that fit the ground you're actually standing on.

Once they're in: catching the frost that would kill them

Picking hardy crops reduces the risk; it doesn't remove it. A sudden hard freeze can still catch tender seedlings or a crop planted a little too ambitiously. With a connected station that's learned your site, Siltwell fires a critical frost alert when the adjusted overnight low for tomorrow or the day after drops to your garden's threshold — worded "adjusted to your station" so you know it's reading your yard, not a regional average.

On the free tier there's no station and no learned offset, but you can still enter a manual temperature offset in Settings if you already know your yard tends to run a degree or two below the forecast — then alerts read "adjusted for your site." It's coarser than a learned bias, but it's better than a raw regional number for a garden you know runs cold.