Frost is beautiful on the hood of an automobile but not something you want to see on tender plant foliage in the Spring!


Frost warnings, issued near the beginning of the summer growing season, keep gardeners on their toes. Since everyone likes to get a head start on the summer garden (perhaps for bragging rights to 'the first tomato') they plant their tomatoes and annual flowers as early as possible. Unfortunately, many of these tender plants will be severely damaged or killed by a late frost.

Frost is more likely to occur in low-lying areas due to the pooling of cold air close to the ground. Therefore, even when there is frost damage in valley gardens, ridge top gardens might be spared. This is one reason fruit growers attempt to locate their orchards in higher locations, so the tender flowers that will someday be fruit, aren't as likely to be 'nipped' by a late frost.


The best defense against frost is not planting too early in the growing season. The rule of thumb in northeastern gardens is to plant tender annuals and vegetable plants on or after Memorial Day. Our best prediction for the last average spring frost in the Pittsburgh area is May 20th. However, during some years annuals could have been planted May 1st without suffering frost damage, while other years a late frost at the end of May could have wiped out tender plants.

Heavy frost is most likely to occur on those cold, clear nights when the stars are bright and there isn't a 'blanket' of cloud cover to hold heat close to the earth. Most weather services will issue Frost Warnings, but it's best to be alert and pro-active if you've planted early, or wish to spare your landscape plants from damage.

In order to cheat nature a bit and get plants in early, there are a few products available that will help, such as row covers and other inventions, that keep heat close to plants and frost away. The most basic way to protect plants in your home landscape is by covering them with a cloth tarp. We've found 10 ft x 10 ft leaf tarps work very well (synthetic burlap). Something like an old bed sheet or pillow case will also work, provided they are light weight and don't break the plant under their weight. Burlap works well also, but must be thoroughly dried before storage. Hanging baskets and potted plants can be moved under a patio roof, or in the event of freezing temperatures, moved inside a garage or house.

Commercial nurserymen often use "frost blankets" to protect their nursery stock during spring cold spells. Trees are laid down and grouped together in a row, then the row is covered with a lightweight, white, synthetic material that resembles landscape fabric. All the edges must be firmly secured with weight (rocks, other potted plants) to prevent the wind from getting under the cover and removing it.


Frost on Red Laceleaf Maple

This is what you don't want to see in the morning since Japanese Maples are very sensitive to frost damage. Notice the spicules of ice on the tender red leaves. Covering this plant with a light tarp or old bed sheet probably would have prevented damage.

Frost on young Beech leaves

Tender beech leaves with frost starting to melt as temperatures warm. Hardy trees will create another new set of leaves, but each 'frosting' weakens a tree and delays new growth.

Frost on Lilac blossoms

Lilac blossoms covered with ice and frost. Nothing ends a spring flower show in your garden like a late frost or freeze.


Freeze damage to plants

Late-season vegetable plants

Starting garden seeds inside

Frequently asked landscaping questions


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