1) These crops need no extra covering or protection unless the temperature goes down to the low 20’s F.: any leafy or root crops such as lettuce, spinach, carrots, turnips. Also crops like peas, broccoli, cabbage and cauliflower will survive light frosts and actually may become sweeter. Continue to harvest into the fall as long as possible.
2) These plants need protection: fruiting crops such as tomatoes, peppers or squash. Other crops susceptible to light frost include the beans, herb basil, and most annual ornamental plants. Perennials are usually fine in a light frost.
3) Frost usually (but not always) occurs on cloudless nights when high pressure moves in. When there is moisture in the air the first frost is less likely (but you never know!).
4) Use a blanket or plastic sheet to protect plants from a light frost but anchor the covering with a brick or rock to prevent it from blowing off.
5) Be sure to remove plastic coverings the next morning as the plants my burn from overheating when the sun comes out. When you do decide you can’t fight the cold any longer harvest all of the fruits and other corps.
6) When you do your final harvest of tomatoes bring them indoors for storage in a cool dark place. Arrange the fruits on some layers of newspaper in a box or tray in a single layer. Stacking the fruits causes pressure and fruit damage which triggers rot! Then, place some more newspapers over the top of the layer of tomatoes. This traps in a natural gas called ethylene which is given off by the fruits themselves. Ethylene also triggers more ripening among other fruits. Some people place an apple among the tomatoes which also helps to give off this ethylene gas. Check the fruits every other day or so for ripening and remove any that are getting soft or showing indications of rot. The fruits with darker green shoulders are the best at ripening and usually have the best taste. Another alternative is to look in a recipe book that might have some uses for green tomatoes. There are many wonderful dishes you can create with green tomatoes!
The first AVERAGE frost date in Cheyenne, Wyoming is September 20th!
Check your local weather service for the date in other areas.