How will this winter’s cold affect your plants?

by Leslie Scharafanow

Chisago County Master Gardener

A couple of years ago, I purchased some heirloom bulbs from a great resource in Michigan called Old House Gardens. If you like unusual or heirloom bulbs, I would recommend that you take a look at their website, oldhousegardens.com, or call for a catalog at 734-995-1486. You can also sign up to receive their e-newsletter. Their latest newsletter discussed how this winter’s cold will affect our plants.  Here is a summary of the article.  The author of the article is not named.

Heirloom plants have been taking extreme weather in stride for decades if not centuries, but let’s take a look at some of the factors that determine how much the cold and snow will affect your plants.

• How cold it got: Of course the colder it gets, the more damage it causes to a wider variety of plants. That’s why average minimum low temperatures are the basis for the USDA hardiness zones. But there’s more to it than that.

• How suddenly the cold arrived: As winter approaches, plants go through a series of bio-chemical changes that prepare them to survive the cold. However, if the cold comes on suddenly, instead of after a long period of slowly dropping temperatures, plants that would normally take it in stride can be killed outright.

• How long the cold lasted: In colder areas, the longer the weather stays cold, the deeper the ground will freeze and the colder it will get down there, which can result in the death of plants that, with a more normal mix of up and down temperatures, would usually survive.

• How bare the soil was: Like a down comforter, snow traps air that makes it a great insulator, which helps to protect against deep ground freezing. Snow also protects bare soil from the cycle of freezing and thawing that occurs when sunny days are followed by much colder nights, which can break roots and heave new plants out of the ground. Wet heavy snow can wreak havoc on the branches of trees and shrubs, but most of the time, where winters are cold, snow is a good thing.

• How well established your plants are: Plants that are recently planted are always more vulnerable to the cold, mainly because they’ve had less time to establish an extensive root system to anchor and hydrate them. That includes woody plants and perennials you planted anytime last year, and especially bulbs and other plants that you planted last fall.

• How hardy your plants are: If you enjoy stretching your hardiness zone and experimenting with plants that are only marginally hardy in your area, you can expect more losses than if you’re a more conservative gardener.

If there is a silver lining, it is that deep cold kills insect pests, and snow replenishes soil moisture.

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