We had a late frost warning in mid-June, which is well past our average spring frost date. We had planted all of our frost-sensitive plants in the garden weeks ago. Suddenly, we were scrambling to protect our garden from the cold threat.
When is it time to protect plants from late spring frosts? Frost sensitive plants like tomatoes, peppers, melons, squash, and cucumbers can be damaged when temperatures fall below 32°F (0°C). Semi-hardy plants like peas, beets, carrots, spinach, lettuce, chard, kale, cabbage, cauliflower, broccoli, celery, and onions are safe until it gets colder than 28°F.
The weather is sometimes a bit unpredictable. This spring we have set records for high temperatures, then just a week later we have 3 days of late frost warnings. It is not “safe” to depend on the average last frost date.
We keep a close eye on weather reports. Because we depend on our garden to feed our family, we protect the more tender plants whenever the forecast is for temperatures of 34°F or below. Any crop lost to a late killer frost can significantly impact our fall harvest.
Six Ideas to Protect Plants from Frost
Insulating the plants against freezing temperatures is the best way to prevent your plants from frost damage. Let’s take a look at 6 easy ways to protect your plants from an impending late spring frost. We invite you to explore them and then be creative and design the perfect protection that fits your garden and your budget.
#1 – Protect Plants with Containers or Cloches
You can select from a wide variety of containers to temporarily cover your plants and protect them from frost. The best containers will provide ventilation and be large enough not to touch the foliage.
You can purchase cloches specifically designed for frost protection here. However, I usually just find creative solutions by repurposing items around our little homestead.
These are just a few ideas of containers that you might want to consider.
Plastic Nursery Pots
One of my favorite ways to protect plants from a late spring frost is with plastic nursery pots. We always have an abundance of them, and they have nice ventilation holes. Plastic pots are light enough that they need to be weighted down with rocks or tied to something to keep them in place.
Ceramic or Clay Pots
Ceramic or clay pots offer ideal frost protection. They have plenty of mass to absorb the warmth from the sun and insulate the plant from outside temperatures. They are heavy enough that they won’t blow away and have a hole for ventilation.
Milk Jugs, Juice Bottles, or Ice Cream Buckets
Cut the bottom off of a milk jug, juice bottle, or pop bottle and you have a free cloche that you can cover your tender little plants with. The top of the container provides adequate ventilation to keep the plant happy. I like to place a stick in the center to keep the wind from blowing the container away.
Ice cream buckets also make a great cloche if you drill a couple of holes in the bottom to provide ventilation for the little plants. I place a rock on the top to make sure that it doesn’t blow away.
I use these containers in a greenhouse technique called “winter sown.” I save the ice cream buckets year after year to start seedlings and to cover larger plants during an impending frost. You can learn more about winter-sown seed starting in our post, Poor Man’s Greenhouse – A Guide to Winter Seed Sowing.
5-Gallon Water Bottles
We have collected a large supply of 5-gallon water-cooler bottles and cut the bottom off of them. This creates a nice protective environment for our tender plants. They fit perfectly inside of our homemade tomato cages and we don’t need to worry about the wind blowing them out of place.
I also use these 5-gallon water bottles in my kitchen garden. I secure them with a bungie cord to the cattle panel arch that they will grow up later in the season.
We leave the bottles over the top of the tomatoes from the time of transplant. During warm weather, we use a garden stake to suspend the bottle over the plants inside of the cages. We simply remove the stake and drop the container down over the plant on cold nights.
We were able to pick these up at a local bottling company for free. It turns out they only use them 5 or 6 times before they have to discard them and I didn’t really care that they are all different and well-used.
You can also purchase them brand new by clicking here or from a local water distribution company.
#2 – Wrap Plants with Insulating Material
Drop cloths, burlap, blankets and sheets can be draped over plants to protect from frost. Be careful that the weight of the blanket does not damage the plants. Be sure to secure it in place.
Garden fleece or horticultural fleece is an inexpensive way to protect your crops. Just unroll this light fabric and cover the plants. It traps the heat but allows water and light to pass through. It can protect plants from several degrees of frost. The fleece is very light and will need to be secured to prevent it from blowing off of the plants.
Plastic sheeting can be used to protect plants as long as you do it correctly. The sheeting must be secured above the plants so that the plastic does not come in contact with the foliage. The plastic sheeting traps heat which protects the plants from freezing. It works well when used correctly.
#3 – Cover Plants with Tarps
We have created expedient plant covers using large tarps. This works well when there is a structure in place (such as the tomato cages or cattle panel arch) to support the weight of the tarp and keep it from crushing the plants.
#4 – Create a Greenhouse
Beth Lestico designed these great A-frame greenhouse covers for raised beds. They can be adapted to almost any size garden bed. The plastic sides can be rolled up during warm weather and then quickly dropped into place when temperatures drop.
Learn more about implementing this design at Step-by-Step Inexpensive Patio Greenhouse or Super Simple Cold Frame.
Tom Bartels uses low tunnels to provide frost protection and extend his growing season. You can learn more about using low tunnels in his biointensive gardening class. Click here to watch a video on his spring gardening tips.
#5 – Bring Plants Indoors
Portable plants should be brought inside a shed, garage, or under a covered patio until the outdoor conditions are safe. Large potted plants are easier to move if they are kept on plant caddies or on wheels.
#6 – Heavy Mulch
Low plants can be temporarily covered with a thick layer of mulch to prevent freezing. Straw and leaves work well as an insulating mulch. Be sure to uncover the plants as soon as the danger of frost is over.
Be Prepared to Protect Your Precious Plants
All it takes is one night where the temperatures drop below freezing to kill your sensitive crops like tomatoes, cucumbers, basil, squash, and melons. When you are depending on the food you grow to feed your family, you must find a way to keep your plants from freezing.
We hope that you have found some of these ideas helpful. The ability to grow your own food is becoming more and more important. You can do this!
Thanks for being part of the solution!Jonathan and Kylene Jones