What Is A Hard Frost: Information On Plants Affected By Hard Frost

Image by Tony Hisgett

By Jackie Carroll

Sometimes plant frost information and protection can be confusing to the average person. Weather forecasters may predict either a light frost or hard frost in the area. So what is the difference and how are plants affected by hard frost verses light ones? Keep reading to find out more about the effects of hard frost, including information on hard frost protection.

What is a Hard Frost?

So what is a hard frost anyway? A hard frost is a frost where both the air and the ground freeze. Many plants that can withstand a light frost, where only the tips of the stems are affected, but most cannot withstand a hard frost. While the effects of hard frost can often be repaired by pruning, some tender plants may not recover.

Hard Frost Protection

You can give tender plants some hard frost protection by covering garden beds with sheets of plastic or tarps that trap the heat radiated by the earth. Fasten covers over the canopies of shrubs with clothespins or spring clips to add a measure of protection. Another alternative is to leave a sprinkler running so that it dribbles water onto your most valuable plants. The water droplets release heat as they cool to help prevent freezing.

The best way to avoid damage is to wait until after the last expected frost before you plant. Frost information is available from a local nurseryman or your cooperative extension agent. The date of your last expected frost is derived from data collected by the U.S. Department of Agriculture over the past 10 years. Knowing your safe planting date is a good guide when you are trying to avoid frost damage, but it is no guarantee.

Plants Affected by Hard Frost

The effects of hard frost that comes later than expected varies with the plant. Once shrubs and perennials break dormancy, they begin producing new growth and flower buds for the current season. Some plants can shrug off a frost with little noticeable damage, but in many cases the new foliage and buds will be seriously damaged or even killed.

Plants affected by hard frost and cold damage may look tattered and have dead tips on the stems. You can improve the appearance of the shrubs and thwart opportunistic insects and diseases by cutting of the damaged tips a few inches below the visible damage. You should also remove damaged flowers and buds along the stem.

Plants that have already spent their resources on bud formation and growth will be set back by a hard frost. They may flower late, and in cases where bud formation began the previous year you may see no flowers at all. Tender vegetable crops and annuals may be damaged to the point where they will not recover and have to be replanted.

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