Sometimes, it's just hard to let the gardening season go. This is especially true when you have nearly ripe tomatoes and eggplants and frost is threatening. You could, of course, harvest what you can and try to ripen them indoors. But if you just have a chance of frost in the forecast, and you know you'd have plenty of decent gardening weather after that frost passes, it's often worthwhile to try to protect your plants right in the garden and extend your gardening season.
The Bubble Wrap Solution
If you're trying to coax your tomatoes, eggplant, or peppers to keep producing despite a frosty night or two in the forecast, this tip is for you. You can often purchase rolls of bubble wrap at office supply stores or wherever you buy moving supplies, such as boxes or packing peanuts. A roll of bubble wrap is usually inexpensive and will provide enough material to protect several plants. In addition, it's reusable; simply store the bubble wrap when you don't need it and use it again the next time frost threatens.
How to Use Bubble Wrap
You need two things to protect your tomato and pepper plants from frost: tomato cages (wood or metal is fine) or sturdy garden stakes, and bubble wrap. The tomato cages or garden stakes will form your structure, and you'll wrap the bubble wrap around that to protect your plants.
The typical metal tomato cages you see in many home centers are essentially useless for actually supporting tomatoes (a vigorous indeterminate variety can turn one into a mangled mess in just a few short weeks), but they work well around pepper plants, which tend to be smaller and more well-behaved than tomato plants. It's best to install the cage when you plant, but you can usually install one over an existing pepper plant at the end of the season without too much trouble.
Once you have the tomato cage over the plant, simply wrap the bubble wrap around the cage, including over the top, using duct or masking tape as necessary to secure it. Wrap it around the cage from ground level all the way up to a few inches above the top of the plant. Cover the top as well.
For large eggplant plants, as well as tomatoes, get yourself a few sturdy wooden garden stakes, and pound them in the soil around the plant. Then wrap your bubble wrap around the stakes and over the top to protect your plant.
The Science Behind the Bubbles
Those little bubbles that make up bubble wrap provide excellent insulation for your plants, buying them a few degrees of warmth, which is often all the difference you need between a plant killed by frost and a healthy plant that will live to see another day. The air trapped between the two layers of plastic is where the insulation value comes from—and the bigger the bubbles, the more insulation you get.
You can also try to protect plants by covering them with sheets, floating row covers, or cardboard boxes. The bubble wrap seems to give a little more protection than these other methods. No matter what you cover your plants with, make sure you remove the cover in the morning—even on cold days, heat can build up under the covers and you'll have the opposite problem: plants that get "cooked" due to excess heat.