Frost Heaving

Much of the damage caused in our gardens during winter is caused by frost, which is a bigger threat to the garden than snow.

Frost or soil heaving occurs after the soil has been exposed to freezing temperatures, and it is the repeated and alternate freezing and thawing of moist soil which creates enough pressure to both expose deep cracks in the soil and push shallow rooted plant roots out of the soil. 

Heaving can leave roots and plant crowns exposed to cold, drying winds as well as possible root breakage. Perennial plants could have their growth stunted by this exposure. 

Poorly established or shallow rooted plants such as strawberries, heucheras, Shasta daisies, and chrysanthemums can be prone to heaving so it is a good idea to have a quick check in the garden to see if any plants have been lifted from the ground or if roots have been left exposed. These shallow rooted perennials may take a few years to establish adequate root systems able to resist lifting during the winter months. 

Many of these effects can be counteracted by applying a thick layer of mulch like bark, wood chips, or shredded leaves around shallow rooted plants towards the end of autumn ahead of the cold, winter spell. It is not too late to apply a layer of mulch now ahead of further frosts. As temperatures warm up in the spring, be careful to keep mulch pulled slightly back from the crowns of perennials that are susceptible to rot. 

A cover of several inches of snow is actually a good insulator against the freeze and thaw cycles that heave plants out of the ground, so be sure to welcome anymore of the white stuff we might get this winter.

Whilst frost may be damaging to shallow roots in the garden, the process of freezing and thawing itself is said to improve and lighten soil structure making it easier for plants to root. The garden always provides a silver lining!

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