How Plant Roots Respond to Cold Temperatures

By James Mitchell · October 18, 2026

Roots in Frozen Soil

When soil freezes, water in the pore spaces between soil particles turns to ice, making it unavailable to roots. However, roots do not simply shut down — they actively respond to cold through changes in membrane composition, gene expression, and metabolic pathways. Understanding these responses helps gardeners protect root systems through winter.

Membrane Adaptation

Root cell membranes contain a mixture of saturated and unsaturated fatty acids. As temperatures drop, roots increase the proportion of unsaturated fatty acids, which remain fluid at lower temperatures. This membrane remodeling is called homeoviscous adaptation and is essential for maintaining nutrient transport and water uptake. Without it, membranes become rigid and leaky, causing nutrient loss.

Water Uptake in Cold Soil

Cold soil dramatically reduces root water uptake for three reasons: increased water viscosity slows movement through soil, membrane permeability decreases, and metabolic energy needed for active transport is reduced. This is why evergreens can suffer winter desiccation — their leaves continue losing water to wind and sun while roots cannot replace it from frozen soil.

Root Freezing Tolerance

Most roots are less cold-hardy than above-ground tissues. While dormant apple tree branches survive minus 40°F, the roots may be killed at 15°F. This disparity explains why mulching is so important — it keeps root-zone temperatures above the killing point even when air temperatures are far colder. Snow cover provides similar insulation naturally.

Mycorrhizal Fungi in Winter

Mycorrhizal fungi associated with plant roots remain active at temperatures where roots alone cannot function effectively. The fungal hyphae extend far beyond the root zone, accessing water and nutrients in micropores that roots cannot reach. Maintaining healthy mycorrhizal associations through fall is crucial for plant survival and early spring nutrient uptake.

Root Growth During Winter

Contrary to popular belief, roots can grow during winter when soil temperatures remain above 40°F. In mild climates and under snow insulation, root growth continues slowly throughout the winter months. This is why fall is an excellent time to plant trees and shrubs — roots establish while tops are dormant, giving the plant a head start for spring.

Frost Heaving and Root Damage

The freeze-thaw cycle in poorly drained soils causes frost heaving — the upward push of soil that lifts shallow-rooted plants out of the ground. Newly planted perennials and strawberries are especially vulnerable. The exposed roots dry out rapidly in winter wind. Mulching after the ground freezes prevents the freeze-thaw cycle by keeping soil temperature stable.

Perennation Strategies

Different plant groups have evolved distinct strategies for keeping roots alive through winter. Geophytes like tulips and daffodils store energy in underground bulbs or corms protected well below the frost line. Tap-rooted perennials like comfrey and horseradish store reserves deep in the soil where temperatures remain stable. Fibrous-rooted grasses survive by maintaining living crown tissue at the soil surface, insulated by dead leaf sheaths.