What is frost heave?
Frost heave occurs after soil has been exposed to freezing temperatures and lots of moisture. The pressure that is created from alternating freezing and thawing conditions lifts the soil and any plants up and out of the ground. Frost heave often occurs in early spring or late fall, when cooler temperatures and soil moisture are common. Heaves can happen in any type of soil; however, soils such as silt, loam, and clay are more prone to heaving due to their ability to retain more moisture.
As cold air sinks into the ground, it freezes water in the soil, turning it into small ice particles. These particles eventually come together to form a layer of ice. When additional moisture from deeper soil layers is also drawn upward and freezes, the ice is then expanded, creating excessive pressure both downward and upward. The downward pressure causes damage to the soil by compacting it. Compacted soil does not allow adequate airflow or drainage within the soil. The upward pressure not only damages the soil structure but also actually creates the frost heave, which is often characterized by deep cracks throughout the soil. These cracks expose the roots of plants to the cold air above. In severe cases, the plants may actually be lifted, or heaved, out of the surrounding soil, where they will quickly dry out and die from exposure.
How do you protect your plants against frost heave?
One of the most effective ways to prevent frost heave from occurring in the garden is by insulating the soil with mulch, such as pine bark or wood chips, or by placing evergreen boughs over the garden. This helps to moderate temperature fluctuations and reduce frost penetration. Another way to help prevent frost heave is by raking out any low spots that may be present. A good time to do this is in the spring and again during fall as you are both preparing for and cleaning up the garden. You should also amend the soil with compost to further improve the soil’s drainage, which lessens the chance of heaving as well. Well-drained soils will also warm faster in spring. Plants should also be chosen for their suitability to cold temperatures such as deciduous trees and shrubs, bulbs, or perennials that are cold hardy.
Unprotected frozen, wet ground is one of the most common causes of death to garden plants in winter due to the havoc created from frost heave. Don’t allow your plants to fall victim to its clutches. Take the extra time to insulate your garden beforehand; it only takes one good frost heave to destroy the garden and all the hard work you put into it.