A fall with above average temperatures and very little snow has now become a sudden winter, plunging temperatures to record lows, not that this temperature is unheard of in winter. It reached -41C in 1939 according to Canada Weather Statistics.  A more common cold snap would take us to -25C for a few days.

Our winters in the Rockies are hard on plants already but this Arctic cold snap is a concern. We still do not have a decent snow cover and that makes these temperatures even more threatening to our more tender shrubs and perennials. The wind chill is another factor, which can severely affect buds and evergreens. I saw this last year on my ornamental Pine, when we had a very early cold snap, with wind that burned the needles of the pine and leaves of my hardy boxwood. The extra wind chill and dry air removes the humidity, which can also help protect the plant, dehydrating it and lowering the temperature even more. The yellow leaves in the spring were the evidence of ’Winter Burn.’ The plants are not dead but recovering a green look will take time.    

There are several factors at play which will affect the more tender plant survival rate.  If plants were well watered in the fall, their roots will be strong and should carry the plant through although it may die back to ground level. The plant also has longer to adjust with soil and water acting as insulating agents. If the plant went into winter with dry roots it may not survive these temperatures. Above ground it is slightly different. When the cells, which make up all parts of the plant  are turgid, (well supplied with water) and it freezes suddenly, the water will turn to ice and the cells will burst, killing the stem, leaf or bud. Underground the soil protects the root and freezing tends to be slower allowing the roots to adjust. If the temperatures drop slowly the parts of the plant above ground can also adjust. This is one advantage we had this winter as, although the temperatures had been above normal, they were below freezing.

Snow cover plays a large factor also and this year we do not have that thick blanket of snow which acts as insulation for the plants both above and below ground. With less insulation, the freezing may well have reached much lower depths in the soil further damaging roots.  

It is a balancing act for the plant and even though many lose their leaves and huddle underground for winter, extremes such as these may well prove too much.

In an effort to show how quickly water freezes in these temperatures, I went and played outside trying to capture a bubble freezing. Other people’s videos are amazing, showing the crystallization as it happens. I had fun but the bubbles were difficult to catch and froze before I had the camera ready. I love the little one that wobbled around and clung to the corner of the tea towel.

Is there anything we can do to help our plants through cold snaps such as this?

Although it is too late for many plants this year, this should be a reminder for the future.

• Water well in the fall. For those of us on watering restrictions that can be difficult but worth the effort. It is not too late to check under eves or overhangs and water those areas that are planted. Those areas dry out over winter. Shovel the snow on the beds if you can.
• Protect more tender shrubs and their buds with a light fabric such a remay, made for the purpose. Bungee cords and clips help to keep the protection in place. Light sheets will work but for any fabric, if we receive a heavy wet snowfall, the weight can bend the plant over and break branches so. Burlap is available in nurseries in the fall and it works well for heavy, sturdy and upright plants.
• Build a shell or tipi structure of branches around small shrubs. I did this with my fir and pine Christmas decorations. Snow, if there is enough, can be shoveled over this to make a little snow shelter.
• Small trees such a Korean Maple, if planted in large pots and placed on rollers, can be wheeled into a garage for winter.
• Mulch the soil with leaves or compost in the fall. Fine bark chips always work well but need to be purchased , when leaves are free and the worms will incorporate into the soil.
• Sometimes we just need to be thankful for the time we had the plant and then replace it.