Frost protection for tomatoes

Question: I planted tomatoes early so I could give them a longer harvest period and the plants froze last week. I understand that we can still get frost until late May. What can I do to protect my next planting?



Answer: Tomatoes, peppers, squash, cucumbers and other frost tender vegetables can be damaged by as little as one degree of frost. There are various ways of covering them with variable amounts of frost protection. Hot caps and clear plastic only give a degree or two of protection. Floating row covers give three or four degrees of protection. Wall-O-Water and similar water jacket protectors can give 10 degrees of protection if the tops are temporarily covered.

In addition to frost protection, row covers and Wall-O-Water trap the sun’s heat inside and speed plant growth so harvest starts earlier.

I prefer floating row covers because they do not need support and are porous so they are easy to water. I even use them on vegetables like beets and other root crops because they keep out the adult flies that lay eggs around the plants which become root maggots.

Another way to speed growth of tender vegetables is plastic mulch. Black mulch works but red or brown mulch is better. Black mulch heats the soil underneath wherever it touches the soil. However, red and brown mulch allow some of the sun’s heat rays to pass through the soil and heat it even faster. The warmer soil increases the speed of plant growth.

An added advantage of colored or black plastic mulch is that they prevent most light from reaching the soil so there is no weed growth. Weed prevention alone is enough to justify the cost and extra effort to install it.

Simply get your soil all ready to plant (including fertilizer), lay plastic mulch over it and cut X holes with your trowel so you can dig a hole for the plant.

By using both plastic mulch and row covers I have speeded up tomato harvest by three weeks.

It is all right to plant seeded tender crops like potatoes, beans and corn now. By the time they are up, we will likely be past frost danger.

Remember, if you harvest the fruit (except for peas) it is frost tender. If you harvest the roots, leaves or flower buds (except for potatoes) it is hardy. It is safe to plant all hardy vegetables now.

It is not so easy to identify frost tender flowers. Zinnia, marigold, impatiens, sunflower, celosia, geranium, begonia and dahlia are the most susceptible to frost. Flowers like snapdragon, petunia, alyssum, dianthus, dusty miller, sweet pea and all perennial flowers are safe to plant now.

For temporary protection of frost tender vegetables and flowers, blankets and quilts give the best protection.

Allen Wilson can be contacted at

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