Frost Cloth vs Fleece: Which Should I Use to Protect My Plants from Frost?

Both frost cloth and horticultural fleece protect plants from cold, but gardeners often use the two terms interchangeably when they actually describe different products with different performance characteristics. Understanding the difference helps you choose the right material for the level of frost you face.

What Is Frost Cloth?

Frost cloth typically refers to a heavier, denser woven or non-woven fabric designed specifically for hard-frost protection rather than general season extension. It is usually sold in weights from 30 to 70 gsm and is more opaque than standard horticultural fleece. The denser weave traps a greater air mass, providing stronger thermal insulation — commonly 4–8 °C of temperature gain on a still night. Heavy frost cloth can protect tender plants down to −5 or even −6 °C when applied without gaps.

What Is Horticultural Fleece?

Horticultural fleece (spunbonded polypropylene) is the lighter, more translucent material typically sold in 17–30 gsm weights. It transmits 85–95% of available light at the lighter weights, making it suitable for use over growing crops during the day without significantly reducing photosynthesis. It provides 2–4 °C of frost protection — sufficient for light to moderate frosts but not reliable below −3 to −4 °C without doubling layers.

When to Use Heavy Frost Cloth

Use heavy frost cloth when hard frost is forecast — typically below −3 °C — and you need maximum protection for tender established plants that cannot be moved indoors. It is particularly useful for protecting established shrubs, container citrus, and trained fruit trees in a cold snap. Because it is opaque, remove it promptly once frost risk passes to restore full light to the plant. Never leave heavy frost cloth on for more than two to three days continuously during the growing season.

Layering for Extreme Frost

For very severe frosts (below −6 °C), a single layer of any fabric is often insufficient for tender plants. Layer a light fleece directly over the plant, then a heavier frost cloth over that, with the edges weighted down. The two-layer system creates two trapped-air insulating zones and can provide 8–12 °C of temperature gain. Adding a layer of dry straw inside the fleece around the crown gives further protection for vulnerable root zones. This multi-layer approach saves plants that would be killed by a single cover.

Practical Tips for Both Materials

Always anchor edges securely — even light wind removes protection almost immediately. Use metal pegs, U-pins, or stones rather than relying on the plant itself to hold the fabric. Cut materials into practical sizes (3 m × 6 m is a versatile working piece) and store in a dry place between uses. Both materials degrade in UV over time: cheap single-use versions last one season; quality reusable versions last four to six seasons with reasonable care.