Frost Heave Is a Hidden Danger That Can Damage Plants – This Easy 'Forgotten' Task Can Prevent It From Happening

The winter weather poses many challenges for plants, as well as for your soil. You may not know that a repeated cycle of freezing and thawing during the winter can even lift plants out of the ground, leaving them vulnerable to the elements. That phenomenon is known as frost heave.

Frost heave can be a plant killer in colder climates. Newly-planted trees, shrubs, and perennials are susceptible, while any shallow-rooted plants are at risk of being lifted from the soil with ease. Thankfully, all it can take is a thick layer of organic matter over the roots to protect them from harm.

Most gardeners are acutely aware of the dangers of frosts and snow, but frost heave is somewhat of a silent killer that doesn’t grab as many headlines. But it can be deadly. We reveal the damage it causes and which plants are susceptible. Plus, how to protect plants from frost so they don’t perish as a result of frost heave.

What Is Frost Heave?

Frost heave occurs due to the repeated process of the soil freezing and thawing. The moisture in the soil expands when it freezes and compacts when it thaws. The pressure this frequent, repeated cycle causes underneath the surface can impact foundations, landscapes, and plants.

When it comes to frost heave affecting plants, Maksim Kazakou, resident botany expert at Plantum, explains how they can find themselves lifted from the ground and displaced.

‘The water in the soil freezes, the soil expands, and the plant gets lifted upward,’ he claims. ‘Even when the soil thaws, the plant doesn’t return to its original position because of the soil around the root system or a large amount of water beneath it.’

Plants can be damaged or even die as a result of frost heave. Damage can occur to a plant’s crown and root systems when exposed to freezing conditions, and unprotected roots can quickly dry out or succumb to frost.

The roots themselves can break as a result of the movement, impacting a plant’s ability to take in water and essential nutrients. It can also lead plants to become loose or unstable, putting them at risk of wind rock during winter.

The plants most susceptible to frost heave include shallow-rooted perennial plants. This includes the likes of coral bells, blanket flower, shasta daisies, strawberries, and scabious.

As well, any recently-planted trees, shrubs, or perennials (including any plants you divided in the fall) are at increased risk of frost heave as they will not have formed a strong root system by winter.

Maksim Kazakou

Maksim Kazakou is a resident plant expert for the Plantum app, which helps users identify plant species, diagnose their conditions, and get specific care advice.

How to Prevent Frost Heave

There are a few simple steps to take to prevent frost heave and keep your plants safe during winter:

• Mulching around plants in the fall helps to insulate the soil and protect the crown and roots from damage caused by frost heave. ‘Mulch the soil around the plant with a layer of organic material like compost, leaf mold, wood chips, pine needles (such as this pine straw mulch at Amazon), or leaves,’ recommends Maksim. ‘This helps prevent sharp temperature fluctuations and reduces heaving caused by the expansion of freezing water in the upper soil layer.’ A thick layer of organic types of mulch will prevent frost from penetrating deep into the soil.
• Give any plants enough time to establish strong roots by planting them at least six weeks before your first predicted frost date. Any plants known to be shallow-rooted are best planted in spring rather than fall, especially if you don’t have enough material to mulch them thickly ahead of the winter frosts.
• Adding organic matter, such as homemade compost, to flower beds or vegetable gardens will help improve the drainage. While homemade is best, you can also purchase bags of compost to use, like this premium organic compost, available at Amazon. A well-draining soil type reduces the amount of water held in the ground that can freeze and thaw. Soil prone to waterlogging is highly susceptible to frost heave.

What to Do if You See Frost Heave

It pays to keep a close eye on your plants over winter to spot the tell-tale signs of frost heave, so you can act fast to limit the damage. Look for signs such as plants sitting higher in the ground, plants leaning or looking unstable, or any roots showing at the surface.

Rebecca Sears, a gardening expert from Ferry-Morse, recommends taking ‘immediate action’ if you notice any signs of frost heave.

‘Start by gently pressing your plants back into the soil during a thaw and covering the exposed roots with more soil,’ she advises. 'Once covered, add a layer of organic mulch, which acts as an insulator and helps moderate soil temperature.

‘Continue to closely monitor your plants throughout the season so you can repeat these steps as needed.’

Rebecca Sears

As CMO and resident green thumb for the Green Garden family of brands, Rebecca Sears nurtures the company's heritage but also looks to develop new products and solutions to help gardeners of all skill levels fuel their passion and become more successful in the garden. Rebecca has been gardening from coast to coast, first realizing her passion while living in Portland, Oregon, inspired by the public gardens throughout the city. When she relocated to the northeast, she built upon her knowledge and craft, and now her backyard garden grows larger each year.

FAQs

What Soil Is Most Susceptible to Frost Heave?

The soil types most susceptible to frost heave are silt and clay soils. These soils hold more water and have small pores between the particles through which water can move easily. To improve the soil health and structure of such soils, adding organic matter is advisable to boost drainage and air movement.

Will Frost Heave Go Down?

Frost heave does go down when the ground thaws, but there is no guarantee that the ground returns to its original position. This unpredictability often leaves plants leaning, loose, or unstable in the ground, or sitting proud of the soil altogether. If you see plants affected by frost heave, try to get them back in the ground ASAP.

Does Gravel Prevent Frost Heave?

To minimize frost heave, incorporating gravel into the soil can improve drainage in beds. This helps reduce waterlogging and the pooling of water, which are conditions that can lead to the damaging freeze-thaw cycles. You can get bags of all-purpose gravel at Ace Hardware that are perfect for landscaping.

Mulching with organic matter is an ideal way to stop soil from freezing in winter, but how can you protect soil in containers?

Thankfully, there are several ways to prevent the soil in pots from freezing and damaging plant roots. These include piling mulch over and around the container, moving pots together for warmth, burying containers in the ground, or covering them with frost cloth, blankets, or winter covers to keep the frost at bay.

One effective option is to use a two-pack of winter plant pot covers, such as these available on Amazon.

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