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What To Do About Frost Heaving

Any plants in your landscape that appear to be protruding from the ground are probably suffering from frost heaving. Frost heaving usually affects perennials but can also uproot shrubs and small, recently planted or shallow rooted trees. It’s caused by the freezing and thawing cycles in winter. The higher the frequency of these cycles, the greater the risk of frost heaving.

Freeze cycles cause soil, especially poorly drained soil, to swell. The soil can only go in one direction – up. This action causes plant roots to lift up with enough force to literally heave them out of the soil. Roots can be torn so that they are not anchored in their hole but exposed to cold temperatures and drying winds. The extent of torn roots depends on their thickness and how firmly they were anchored. I’ve seen shallow rooted trees uprooted and leaning against houses.

Planting or dividing perennials too late in the fall or not mulching them sufficiently is the most common causes of frost heave. To repair frost heaved plants, try to stand them back upright, backfill soil around the roots, tamp it down and mulch. It may also need supplemental support, such as staking.

If the plant is completely out of the ground or leaning in such a way that it can’t be stood back upright, cover the exposed roots with plenty of soil and a three- or four-inch layer of mulch. Seasoned wood chips are the best mulch for this. Some recommend using straw, but I prefer wood chips. They weigh more than straw so they can hold the soil in place better than straw. Wood chip mulch also moderates soil temperature, reducing the chance of a reoccurrence. As they decompose, wood chips add organic matter to the soil. Improving the soil also can reduce the chances of frost heaving happening again.

The repairs recommended here are probably only temporary. Plants that you were able to stand upright may grow new roots and be fine. Watch them for a growing season, making sure they’re firmly in place next fall. Remove any staking as soon as they’re firm enough to stand on their own. Plants whose exposed roots you just covered when they heaved must be replanted in the spring. If one you stood up doesn’t look as though it’s returning to health, dig it up and replant it.

If this is a job you’d rather not tackle, our landscape professionals can assess the damage caused by the frost heaving and give a prognosis of each plant’s chance of surviving. We can then make temporary repairs to those that can be saved. In spring, we can come back and make permanent repairs to the survivors or replace those that didn’t survive.

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