Mulch reduces frost heave

Q. My plant is coming out of the ground. What should I do?

Loretta from Campbell

A. During nicer winter days (yes we have some) I like to go out and look around my garden and flower beds to see how the plants are doing. Occasionally, like Loretta, I’ll find a perennial that looks like it’s being pushed up out of the ground with its crown and some roots exposed. I know that the perennial was healthy and the roots covered last fall. What is going on here?

The answer is frost heave. Actually it’s not much different than it sounds. Due to wide temperature fluctuations in the winter, exposed soil surfaces freeze and thaw repeatedly. This repeated freezing and thawing causes the soil to expand and contract, which can lift up or heave some perennials out of the soil. Frost heaving is a powerful process that can affect the whole landscape. It can push fence posts out of the ground and buckle roads. In New England, repeated frost heaving pushed up a bumper crop of ancient rocks deposited by glaciers thousands of years ago. These “New England potatoes” are a nuisance in farm fields, and with wood in short supply, farmers piled up the stones to make the distinctive stone walls (instead of fences) found in the region.

As far as plants go, frost heaving may break off some of the plant’s roots. It can also expose the plant’s crown and remaining roots to cold temperatures and drying winds. Freezing and drying injury to a plant’s roots and crown may seriously damage or destroy perennials. Recently planted perennials are more susceptible to frost heave damage than established ones.

To help prevent frost heaving from damaging plants this time of year, inspect your garden perennials after hard freezes. If plants are heaving, place soil around the base of the plant to cover any exposed roots. Then cover the plants with several inches of mulch, straw or pine needles to prevent further freezing and thawing cycles in late winter.

The best way to avoid frost heave damage is prevention. Next fall, apply mulch to newly planted garden perennials after a couple of hard frosts. The weight of the mulch will keep the plant crowns and roots in contact with the insulating soil. The mulch also will help moderate soil temperatures, limiting frequent freezing and thawing cycles, and ultimately help keep the plants in the ground where they belong. To learn more about preventing frost heaving and plants that are most susceptible to this, go to: http://go.osu.edu/heave

Today’s answer is provided by OSU Extension master gardener volunteer David Sprague. Call the office hot line at 330-533-5538 to submit your questions. Clinic hours vary this time of year due to the winter season.