Garden covers like frost cloth and floating row covers are an excellent way to protect plants from frost.7 Covering plants with blankets or using cloches can also effectively protect them from frost damage.5
A cloche is a small, portable, protective structure made of glass or rigid transparent plastic.3 Protecting plants from freezing temperatures can prevent damage, extend harvests, and help you enjoy your garden longer.4
With some preparation, you can avoid last-minute panic and safeguard your cherished plants from harm.1
What Frost Does
Frost occurs when ice crystals form on the surface of a leaf.4 It can happen even when air temperatures are slightly above freezing, as long as the plant surface cools to the freezing point.4
Frosts generally cause minor damage, but they can harm sensitive species, especially flowers and flower buds.4 A freeze is more damaging than a frost.4
A frost in early fall may be followed by days of warm weather, while a spring warm spell can trigger new growth before another hard freeze arrives.4
Know Your Frost Dates
First, learn approximately when your location typically gets frost.1 A frost dates calculator shows the local average frost dates for both spring and fall.1
Many weather sites base their frost dates on a 50 percent chance of frost.1 One calculator assumes a 30 percent probability of frost instead.1
Fall Gardening: Protect Plants
Covers allow you to grow further into the fall or winter.7 Frost cloth and floating row covers also shield plants from sleet, snow, and cold winds.7
Tender plants should be brought indoors when low temperatures are forecast.5 They can also be insulated.5
Some vegetables are particularly vulnerable to frost, while some crops can even benefit from frosty conditions.1
Spring Gardening: Protect Plants
Covers also let you start earlier in late winter or spring.7
Warm the Soil
Pre-warming the soil in spring can help crops germinate, or sprout, earlier than usual.3 It can also add 3 to 4 weeks to the cropping season at either end, the stretch when crops can grow.3
Warming the soil also helps you make maximum use of available ground.3
A cloche can raise the local soil temperature by up to 10°C and hasten germination.3 Cloches are used to protect plants, especially early vegetables, from wet and cold weather.3
If you use a glass cloche, set it where children and pets cannot knock it over. Read the instructions on any cover you buy, and store covers and cloches out of reach of children and pets.
Cabbage Seedlings
Mature cabbage is hardy, meaning it copes with cold, but its seedlings are sensitive to frost.
Start cabbage seeds indoors 6 to 8 weeks before your last spring frost date. Then transplant them 2 to 3 weeks before the last spring frost in your area. Do not plant too early.
Uncover Plants in the Morning
In the morning, it is important to remove the covers.6 On frosty mornings, the sun almost always rises into a clear sky.6
The sun can quickly overheat plants left inside of a cover.6 Covers with small holes on the top release excess heat, which makes them safer to use after sunrise.6
Mistakes to Avoid
- Leaving covers on after sunrise, because the sun can quickly overheat plants left inside of a cover.6
- Planting cabbage seedlings too early, since mature cabbage is hardy but its seedlings are sensitive to frost.
- Overlooking flowers and flower buds, which frost can damage in sensitive species.4
- Leaving tender plants outside when low temperatures are forecast, instead of bringing them indoors or insulating them.5
- Going without covers when sleet, snow, or cold winds arrive, since garden covers protect plants from each of them.7
Quick-Reference Checklist
Pin this list near your garden door and run through it before each cold night.
Before the Season
- Look up your local average frost dates for spring and fall.1
- Prepare early so you can avoid last-minute panic.1
- Check flowers and flower buds, which frost can damage in sensitive species.4
On Cold Nights
- Cover plants with blankets or cloches to protect them from frost damage.5
- Bring tender plants indoors or insulate them when low temperatures are forecast.5
- Use frost cloth or floating row covers to protect plants from frost, sleet, snow, and cold winds.7
- Use covers to grow further into the fall or winter.7
In the Morning
- Remove the covers in the morning so the sun cannot overheat your plants.6
- Choose covers with small holes on top, which release excess heat.6
- Do not leave plants inside a cover after sunrise, because they can overheat quickly.6
In Spring
- Use covers to start earlier in late winter or spring.7
- Use a cloche to warm the soil before planting, especially for early vegetables.3
- Pre-warm the soil in spring to help crops germinate earlier than usual.3
- Start cabbage seeds indoors 6 to 8 weeks before your last spring frost date.
- Transplant cabbage 2 to 3 weeks before the last spring frost in your area.
- Remember that cabbage seedlings are sensitive to frost, even though mature cabbage is hardy.