Winterizing tips to help plants endure chilly days

By Jennie Hagen November 09, 2011 12:44 am

A gardener’s life is usually dictated by location and weather, only one of which we have some control over. This leaves us with weather, and the fact that our growing season is basically over for all areas of Union, Wallowa and Baker counties. For those of you with greenhouses or cold frames, the season can, at times, be extended almost indefinitely with the correct insulation and the structure’s aspect to the lower winter sun. For the rest of us, here are a few winterizing tips to ensure your plants survive the days of cold.

One can never say enough good about mulch. It insulates and decreases a plants need for water. When additional mulch is applied after the ground has frozen, it protects surface roots from frost heaving and exposure during the long winter months. Frost heave is the result of water particles in the soil surface expanding as they are frozen, with the typical soil-heave that is then noticeably visible. Additional mulch applied prior to our ground being frozen may actually be a detriment as most plants in our area, whether native or introduced, need the full protection of non-growth for a minimum of three months. Living in frozen soil is their way of staying dormant and protected.  For younger, smaller plants, most bulbs and any new landscaping you have done, it is essential that the top feeder roots be protected from the continual freezing and thawing that occurs in the top six inches of soil when a warm spell comes along.

Remember last February? While we loved the few 70-degree days, pre-seasonal warming can damage significantly the top layer of roots.  This occurs when the plant is signaled, by the warmer temperatures, to sprout those early feeder roots. Then a week later, when the ground refreezes, they are killed.

How much mulch, and the depth you need, is again a matter of what you are protecting.  Newly planted bulbs, such as hardy daffodils or tulips, may not require as much as their new roots are probably below the top six inches of soil. For smaller bulbs like grape hyacinths and fritillaria, another four or more inches should be sufficient. The key here is that you want the ground to stay frozen until next spring and full seasonal thaw.

Perennials planted this fall should also be top-dressed with additional mulch, again, after the ground has frozen.

Do you have perennials in pots that you want to over-winter? Be sure to place them against a structure, preferably clustered together, where you can cover them if needed. As most of us have the drying winter winds to contend with, a good watering of these plants in pots is essential before they freeze. Try to place them where they will also stay frozen. If you have smaller plants in pots that you want to try and over-winter, put these in the center of the cluster, or between larger pots to afford them greater protection.  Covering is usually done to protect from the wind and wind damage to stems you don’t want broken. Having moved into our current home just last November, I was forced to do this with about 20 plants I didn’t have the opportunity to get planted prior to the ground freezing. I was pleasantly surprised that almost all survived, although a few were broken from the wind.

Until next time, have fun perusing all the catalogs that are arriving. I know I will.


Jennie Hagen is a Grande Ronde Valley gardener.