Science

How do trees survive freezing winters without moving?

Rive News Research Desk

Published October 31, 2026 · 8 min read

By Rive News / Research desk | Rive News / Published October 31, 2026 at 9:00 AM PKT

Key takeaways

Trees survive freezing winters by going dormant, moving water out of living cells, and sweetening cell sap into a natural antifreeze.
Some tissues supercool, staying liquid down to about -40 F; below that, ice forms spontaneously and cells die.
Only living cells need protection; the dead wood of the trunk can freeze solid without harm.

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A tree is roughly half water. Water freezes at 32 F. And a tree cannot walk south for the winter. So how does a maple in Vermont or a birch in Alaska sit through months of subzero nights and leaf out again in spring?

The answer is a staged defense that starts in late summer, long before the first frost. Trees rewire their cell chemistry, relocate water, and in some tissues stay liquid well below freezing. This article explains why winter is lethal to cells, how dormancy starts the defense, and the three mechanisms researchers say keep living cells alive, including the antifreeze proteins and deep supercooling that most plain-language explainers skip.

Why winter is lethal to living cells

Freezing kills plant cells in a specific way. When ice crystals form inside a living cell, they shred the cell membrane, and the cell dies. That makes intracellular freezing the central threat of winter, as Iowa State University plant scientists put it in a classic extension publication on woody plants.

Trees manage the problem by accepting a split outcome. Much of a tree's trunk is dead wood already, and dead cells can freeze solid without consequence. The job of winter survival is narrower: protect the small percentage of living cells in buds, the cambium layer under the bark, and fine twigs. As Northern Woodlands reports, there are living cells in a trunk that remain unfrozen even while sitting at the same temperature as neighboring dead cells that are frozen solid.

Cold acclimation begins gradually. According to Iowa State, the first stages are triggered in early autumn by short days and nonfreezing chilling temperatures, which stop growth. But a tree becomes fully cold-hardy only after exposure to at or below freezing temperatures for some time. A warm autumn followed by a sudden hard freeze is dangerous precisely because the tree has not finished preparing.

Dormancy: the controlled shutdown

Dormancy is the tree's version of hibernation. As days shorten, the tree slows its metabolism, stops producing chlorophyll, and for deciduous species, drops its leaves. The Haverford College Arboretum describes abscission, the technical term for leaf drop, as a way to retain water and energy through the cold months.

Evergreens take a different route. Their needles carry a waxy coating that limits water loss, so they can keep photosynthesizing on mild winter days without the broad-leaf water bill. Either way, the tree switches its genes: growth programs turn off, and cold-survival programs turn on. Tree-care researchers note that dormancy does not mean inactive. The tree is working, just on defense instead of growth.

Water migration: moving the freezable water out

The first active defense happens inside the cells. Paul Schaberg, a research plant physiologist with the USDA Forest Service's Aiken Forestry Sciences Laboratory in Burlington, Vermont, has led investigations of cold tolerance in montane spruce and fir. His work points to three basic defenses, and the first is water migration.

During cold acclimation, cell membranes become more pliable. That flexibility lets water move out of the living cells and into the spaces between them, where it can freeze harmlessly. The cells shrink as water leaves, which makes room for the expanding ice and reduces pressure on the cell walls. A tree service summary of the science describes the membranes as being squeezed by the ice but not punctured, because of that winter flexibility.

Some trees go further and designate sacrificial zones. Vulnerable cells become the nucleation points where ice starts, and since moisture is drawn toward existing ice, freezing concentrates in those areas while the important cells stay protected. It is controlled damage, confined to places the tree can afford to lose.

Sugar antifreeze and antifreeze proteins

Once water has migrated out, what remains inside the cell gets sweeter. In autumn, the tree converts stored starches into soluble sugars, and the cellular fluid becomes a concentrated syrup. The sugars lower the freezing point inside the cell, the same way antifreeze lowers it in a car radiator, as Iowa State's publication puts it.

The concentration is extreme. Tree physiologists describe the sugary liquid turning viscous, thick like molasses, in the words of one arboriculture report. At full acclimation the fluid becomes so dense it approaches a glassy state, similar to how silica stays liquid while looking solid when supercooled into glass. The liquid cannot easily crystallize, and crystallization is what would destroy the cell.

Some species add a further trick. The Haverford Arboretum notes that certain trees produce their own antifreeze proteins, molecules that bind to tiny ice crystals and stop them from growing. These ice-binding proteins are the least covered part of the story in popular explainers, but they are a documented part of the cold-tolerance toolkit in several woody species.

Deep supercooling down to minus 40

The third defense is the strangest. Some tree tissues supercool: their water stays liquid below the freezing point because there are no suitable nucleation sites for ice to begin forming. Iowa State lists oak, elm, maple, beech, ash, walnut, hickory, apple, pear, peach, and plum among species whose buds and twigs use deep supercooling.

There is a hard floor. Cellular water can supercool only to about -40 F, at which point ice forms spontaneously no matter what, and the cell dies. That -40 F limit is not trivia. It explains the existence of timberlines at high elevations and low-elevation timberlines in places like Alaska, where species that rely on supercooling simply cannot grow below that threshold.

Trees in the very coldest places use a different strategy entirely. Paper birch, willow, and quaking aspen in northern Canada and Alaska endure minimums well below -40 F. Instead of supercooling, they depend on the dehydration mechanism, tolerating extreme water loss from their cells as freezable water crystallizes in the intercellular spaces. The hardier the plant, the greater its cells' capacity to tolerate dehydration, according to Iowa State.

How extreme can acclimation get? "At this stage where trees are fully cold-acclimated, you can put them into liquid nitrogen and they would survive," says Sally Aitken, a forestry professor at the University of British Columbia. The quote comes from an arboriculture report on winter tree biology, and it captures how complete the transformation is.

What kills trees anyway

If the defenses are this good, winter damage should not happen, but it does. The pattern is instructive. Sudden harsh frosts after mild spells are particularly risky, because tissues that deacclimated during the warmth have not re-hardened. Late spring frosts kill tender new growth for the same reason: the tree has spent its defenses and resumed growing.

Roots get help from the ground. Soil acts as a thermal buffer, keeping root temperatures higher and more stable than air temperatures, and snow cover insulates further. But an open, snowless winter with brutal wind can still damage roots and desiccate evergreen foliage. The tree's defenses are tuned to its local climate, which is why planting a species outside its hardiness zone is a gamble the tree usually loses.

Why don't trees freeze to death in winter?

They do freeze, just not where it matters. Water between the cells freezes routinely, and dead wood freezes solid. The tree's three defenses, water migration, sugar antifreeze, and supercooling, keep ice out of the small fraction of cells that are alive.

What temperature can trees survive?

Fully acclimated woody plants in the northern United States commonly tolerate midwinter lows near -40 to -50 F, per Iowa State. But supercooling fails at about -40 F, and species beyond their hardiness zone die well above that.

Do trees make their own antifreeze?

In a sense, yes. They convert starch to sugars that lower the freezing point of cell sap, and some species produce antifreeze proteins that block ice crystal growth. It is chemistry, not a separate fluid, and it only works once the tree has acclimated.

Why do sudden frosts hurt trees more than deep winter cold?

Deep cold arrives after weeks of preparation. A sudden frost after a mild spell catches tissues deacclimated, with water back inside the cells and membranes less flexible. Ice then forms where it can kill.

The bottom line

Trees survive freezing winters by preparing for months: shutting down growth, draining water from living cells, sweetening the remaining sap into antifreeze, and supercooling tissues down to about -40 F. Only the living cells need saving, and the tree is ruthless about prioritizing them. Gardeners can help by planting species rated for their zone and mulching roots, but the heavy lifting is chemistry the tree worked out over millions of years.

Topics: tree biology, winter survival, plant science

The Rive News research desk writes explainers from published scientific and extension sources. We do not conduct field research.

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