A frost blanket is one of the most useful tools in any gardener's arsenal. A single layer of the right fabric can protect vegetables, flowers, and tender perennials through frost events that would otherwise cause serious damage. This guide helps you choose the right weight, size your coverage correctly, and know when fabric protection is enough — and when it isn't.

What Is a Frost Blanket?

A frost blanket is a lightweight non-woven polypropylene fabric designed to trap warm air close to plant foliage during cold nights. The fabric works by slowing the rate of heat loss from the soil and plant surfaces, creating a microclimate several degrees warmer than the ambient air temperature.

Unlike plastic covers, frost blankets are permeable — they allow light, air, and water to pass through. This means you can leave them on plants for days or weeks without damage, and plants receive adequate conditions for growth even while covered.

Frost blankets are the same product sold as "floating row cover," "frost cloth," and "season extender." The different names reflect different use contexts; the product is identical.

Temperature Protection by Weight

These are approximate values assuming the fabric is laid directly over or around the plant with edges secured to trap ground heat. Wind and elevating the fabric on hoops can reduce effective protection. Securely anchoring all fabric edges significantly improves performance.

Which Weight Should You Choose?

0.5oz — Season Extender

Use 0.5oz when your primary goal is season extension rather than hard frost protection. It transmits the most light of the four weights and can stay on crops all day. Best for: spring seeding protection from light late frosts (down to roughly 28–30°F), fall crops staying productive through light frosts, and summer pest exclusion. Also used as an insect barrier for crops like brassicas and carrots.

1oz — Standard Home Garden Choice

The most popular weight for home vegetable gardens. Provides adequate protection for most frost events in USDA zones 5–9. Light enough to leave on growing crops for days at a time. Use 1oz when nighttime lows will drop to roughly 26–28°F.

1.5oz — Moderate Hard Frost

Step up to 1.5oz when lows will reach roughly 24–26°F, or when protecting tender plants like basil transplants, pepper seedlings, or frost-sensitive perennials. Also a good choice for fall protection in colder climates where 1oz may not provide enough margin.

2.5oz — Maximum Fabric Protection

The heaviest weight Pro Fabric Supply carries. Use 2.5oz for the coldest events you'll protect with fabric (lows to roughly 22–24°F). Should be removed during the day if possible, as lower light transmission can stress plants under extended cover. Ideal for: protecting tender perennials through a brief severe cold snap, covering citrus trees overnight, or providing maximum protection for a crop you cannot afford to lose.

Coverage Calculator

For raised beds and garden rows

The blanket should extend 6–12 inches beyond each side of the bed to anchor it securely. More extension = better edge seal = better protection.

• 30-inch wide bed: use fabric 54–66 inches (4.5–5.5 ft) wide minimum
• 48-inch wide bed: use fabric 72–84 inches (6–7 ft) wide
• Row crop (single row): use fabric at least 24 inches wide for low crops, 36–48 inches for staked plants on hoops

For length: add 3–4 feet to the bed length to allow for anchoring at both ends.

For individual container plants

Measure the widest point of the pot plus the height of the plant foliage. Add 12 inches for tucking under the base of the container. A 5-gallon container with 2-foot tall plants needs approximately 4–5 feet of fabric in each direction.

For shrubs and garden beds

For irregularly shaped planting areas, measure length × width and add 20% for tucking and overlap. Two people can install most blankets more efficiently — one holds the fabric taut while the other anchors the edges.

Roll Sizes Available

Pro Fabric Supply frost blankets are available in widths from 3 ft to 50 ft and lengths from 100 ft up to 2,000 ft, depending on weight:

Width Range	Best For
6–7 ft	Single raised beds, small row crops, home gardens
10–14 ft	Multiple rows, wider beds, small market gardens
20–30 ft	Large garden beds, low tunnels, small commercial operations
36–50 ft	Full commercial field-scale coverage

Roll lengths run from 100 feet for home garden use up to 2,000 feet for commercial rolls — for example, 36' × 1,000' or 50' × 1,000' for field-scale applications. Call Pro Fabric Supply if you need a specific length not listed on the product page.

When to Bring Plants Inside Instead

Even the best frost blanket has limits. Bring container plants inside when:

• Forecast lows below roughly 22°F — below the reliable protection range even of 2.5oz fabric
• Extended cold: more than 48 hours below freezing without warming above freezing in between (soil under fabric eventually equilibrates to ambient temperature)
• Tropical plants sensitive to chilling injury (not just frost) — many tropicals are damaged below 50°F even without frost
• Container plants: pots freeze faster than in-ground soil; the container provides no soil heat buffer

For in-ground plants, frost blankets are more effective because they benefit from the ground's thermal mass staying above freezing for much longer than ambient air.

Frequently Asked Questions