Grow Something • Spring 2026

Raised beds change the rules of winter dormancy. Here is what your plants actually experience, and what to do about it.

You moved your plants outside for winter. Maybe it was a perennial you wanted to harden off, a pot of herbs you hoped the cold would not kill, or a whole raised bed you planted in fall and left to fend for itself. Now you are wondering what is actually happening to those plants and whether they will come back. Collecting seeds for the spring and seeing what can last outside is part of the journey. 

The short answer is that your plants are resting, not dying. The longer answer is that raised beds change how that rest works, and in some ways they make winter harder on plants than an in-ground garden would. Understanding the difference tells you exactly what to do.

What Dormancy Actually Means

When temperatures drop and day length shortens, most plants shift into dormancy. Growth stops. Water and nutrient uptake slows to almost nothing. Energy the plant stored through the summer stays locked in the roots until conditions improve. A dormant plant that looks dead is almost always just waiting.

Dormant plants want cold and stable, not fluctuating. A plant that freezes solid every night and thaws every afternoon is under far more stress than one that stays consistently cold. Raised beds in full sun can trigger this freeze-thaw cycle daily, which is exactly the problem.

Why Raised Beds Are Harder on Plants in Winter

In the ground, soil acts as a massive thermal buffer. Roots in the ground can retreat from surface cold and shelter in warmer soil below. Raised beds do not offer this protection. The soil in a raised bed is exposed on four sides, not just the top. In a hard freeze, a twelve-inch raised bed can freeze solid from edge to edge.

The two-zone rule for raised beds: select plants rated hardy to at least two full zones colder than your actual zone. If you are in Zone 7, choose plants rated to Zone 5. The exposed sides of a raised bed lose heat fast enough to make the effective hardiness behave like a significantly colder zone.

The Three Things That Will Actually Kill Your Plants

Frost heave. When water in the soil freezes, it expands and can push root balls up out of the soil. A two-to-three inch layer of mulch, straw, or shredded leaves across the top of the bed prevents this entirely.

Freeze-thaw cycling. A plant that freezes at night and thaws in afternoon sun is not resting. It is repeatedly stressed. Cell walls rupture during rapid temperature changes. If your raised bed sits in a location with strong afternoon sun in winter, consider temporary shade cloth during cold stretches.

Late or early frost on new growth. A warm February can trick plants out of dormancy early. Then one hard frost in early March kills every bud and shoot that opens. Keep a cheap outdoor thermometer near your raised bed from February onward. If new growth is emerging and frost is in the forecast, cover the bed with an old bedsheet before sundown.

What to Do Right Now

Mulch the surface now if you have not. Two to three inches of straw, shredded leaves, or wood chip mulch insulates the soil, prevents frost heave, and moderates temperature swings. Straw bales from a feed store run three to five dollars and cover a large raised bed completely.

Leave the dead tops standing. Crispy brown stalks act as insulation and trap fallen leaves and snow. Wait until late winter, when you see new growth emerging at the base of plants, before cutting anything back.

Water once, then mostly stop. Dormant plants need very little water, but soil that is bone dry going into a hard freeze is more vulnerable than moist soil. Give the bed a good deep soak before the first hard freeze. After that, water only during extended dry periods with temperatures staying above freezing.

Insulate the sides of the bed. Pile leaves, straw, or compost against the outside of the walls to buffer heat loss. If you have a metal bed, wrap it with burlap or old moving blankets during the coldest stretches.

When to Worry and When to Wait

In late winter, when everything in your raised beds looks black and dead, the impulse is to pull it all out and start fresh. Resist it. Roots survive long after tops die. The test is simple: scratch the stem near the base with a fingernail. If you see green beneath the surface layer, the plant is alive. 

The right time to do a hard cleanup is when you see consistent new growth emerging at the base of plants. Cut the dead tops back then, pull the mulch back slightly to let the soil surface warm faster, and let spring take over.

Reference: Fine Gardening — What Happens to Plants in Winter