You can extend the growing season of some frost-intolerant plants by planting them before the last frost in spring and/or continuing them beyond the first frost in the fall if you cover them during cold spells. There are a couple of devices you can purchase or make that will protect them from the cold and frost.
A cloche is a portable cover that is gently pressed into the soil and over (usually) one plant. Manufactured cloches are usually made of glass, and they come in a variety of sizes and shapes, such as bells and pyramids. In a pinch, you can use any clear plastic or glass container. Ensure that you remove them during warm weather, as plants can overheat and burn under the glass when the sun is on them.
Cold frames may be permanent or portable. Unlike cloches, they usually have walls that extend into the ground, so they keep both the plant and its soil and roots warm.
Portable versions can be made by arranging hay or straw bales on the edge of the garden and then resting storm windows on top of the bales. You can pull the windows apart a bit to let air in on warmer days, and close them tightly on colder days.
Permanent versions are often made by inserting wooden walls directly into the ground, then attaching old storm windows to them by means of a hinge that can be propped open or ajar, or closed, depending on the weather. You can buy or make many types of cold frames.
Here are some more examples of plant protectors, both premade versions, and those you can make on your own to suit your particular garden:
- PVC and greenhouse film covers
- Cloches and cold frames
- 10 cold frame plans
- Plastic-covered cold frame