Not long ago, we flirted with frost. We didn’t quite get there, but it may not be long now. Here in Huntsville, our average first frost is November 1st. Of course that’s an average, not a guarantee, and if you have vegetation you want to protect you need to be ready now, particularly if you are in the higher elevations of Rainbow Mountain, Green Mountain or Monte Sano, or are in southern middle Tennessee. When a frost warning comes, it’s usually too late to figure out what you are going to do.
There are several types of foliage you want to protect from frost:
- Tropical plants. These should be brought inside when the temperature drops below 40F, and many will appreciate not being in temperatures even that low. If you have tropical or out of zone plants in the ground outside, they probably won’t survive the winter. You can increase their chances by giving them a very thick insulating blanket of straw or leaves. A sheltered position or warm microclimate can also help.
- Frost sensitive plants. At first sign of frost, these plants are dead. This can include both garden annuals and tender perennials.
- Frost tolerant plants with fruit. Frost tolerant plants are our cold weather garden friends, but some of them will have fruit that will be damaged by frost. English peas are a prime example of this kind of plant. You can still eat the peas, but they can get freezer burn right on the vine.
The goal of frost or freeze protection is to capture warmth rising from the earth, creating a pocket of frost-free air. Don’t tuck material around the plant, spread it out and secure it carefully to the ground. The wider the pocket you make and the fewer gaps the wind can blow in and under, the more warmth you trap.
You have several options for doing this, listed from best to worst:
- Floating row cover like Agribon breathes well and is very light so it won’t damage more fragile vegetation when laid directly on it. Because it breathes, you can leave it out over multiple days without worrying about cooking your plants in the warm daylight sun. It comes in multiple weights, and can be simply staked down over the plants or raised off the ground with hoops or wire. Be sure it’s carefully secured with stakes, as it is plenty light enough to blow off in the night and ruin your work. The heavier the weight of the fabric, the more protection. It’s not a cheap material, but if well cared for it can last multiple years and requires little storage space. (It also has other uses: if cabbage worms are eating your garden up, you can cover these cole crops and prevent flying moths from laying more eggs. It can be used to provide shade on hot spring days.)
- Big old cloths, like sheets and towels, can also work. If you don’t have extras, the thrift store probably does. If it isn’t going to rain, sheets are light enough to be laid directly on many plants. Otherwise, prop them up somehow over the plant. Hoops of wire stuck into the ground are a popular option. Last year, I used old towels and upside down milk crates to protect my tiny tea camellias from those extra cold nights.
- Newspaper is a fairly poor choice, but it’s often household waste and can still be composted afterwards. You need to be able to successfully prop it up away from the plants, and not leave it out for long past daylight since soggy newspaper and sunlight may steam your plants. You will also have to re-do it for each new frost.
- Plastic is a last resort. Unless you are creating a ventilated mini hoop house, plastic must be removed at dawn and not applied until dusk. Plastic + sunlight can rapidly overheat and kill plants.
At some point, it’s time to let your tender plants go and move to more seasonal crops. In my garden, the only warm weather plants still going strong are sweet potatoes and peppers. When cold sets in, I will pick all the peppers, since they are slower to ripen with cooler days and are no longer setting new fruit. I won’t push my way through the sweet potato jungle until frost kills the vines and it’s easy to harvest.
But that could be a month or more away. In the meantime, be prepared to take action while you enjoy the mild fall weather and the fresh cold season roots and greens coming out of your garden.