Winter may finally be coming to the West Coast!
We may have gotten a little ahead of ourselves with the anticipation of spring!
According to the forecast for this coming week, temperatures may drop as low as -10 °C, so perhaps now is a good time to talk about how to protect your more tender plants from the cold. *Scroll to the bottom for our list of QUICK TIPS on winter protection.
If you’re uncertain which of your plants require extra protection, look up their hardiness zone. Most of the lower mainland is around Zone 8 but even hardy plants may have trouble coping with this weekend’s weather if they have broken dormancy. Here is a useful link for looking up plants in our zone: http://www.planthardiness.gc.ca/
Plants that have broken dormancy prematurely (induced by recent stretch of mild weather) are more vulnerable to a cold snap. Broadleaf evergreens are also generally more sensitive to cold than deciduous plants (which lose their leaves in winter) or conifers. Flowers and buds that are about to open also tend to be more sensitive to cold damage.
This occurs as a result of water freezing in the plant’s tissues, causing cells to rupture. If this type of injury occurs above ground, branch tips and foliage will be damaged. If the plant’s roots freeze beyond their innate tolerance, the entire plant will likely die.
The soil absorbs heat during the day and releases it at night, so trapping this heat with insulation may prevent damage to tender foliage. A layer of mulch protects the roots, while a layer of crop cover fabric laid out over plants traps some heat released during the night keeping the foliage a few degrees warmer than the surrounding air. Thick synthetic fabric crop covers are well-suited to insulating plants in this manner, while still allowing penetration of light and water.
This occurs from heavy wet snow accumulating on foliage and branches, causing them to be weighed down and break. Broadleaf evergreens like Evergreen magnolia are especially susceptible, as are evergreen shrubs and hedges that have a columnar or bushy rounded form to them that do not readily shed snow as it accumulates.
After a snowfall, take care to gently knock off any snow accumulation using a broom. You can also use twine to bundle up hedges so upright branches do not bend over and break with the weight of the snow.
When water in the soil is frozen, roots are not able to take it up to replace moisture lost through the leaves (a natural process called transpiration). Transpiration naturally slows when the weather turns cold, but winter winds, especially combined with sunny weather, accelerate desiccation by drawing moisture out of the leaves at a faster rate than the plant can replenish. This results in damage to the foliage and tender stems, called winter burn.
Since wind is the real culprit for causing winter burn, we can mitigate this type of damage by providing a wind break. This can be done easily by putting stakes round the perimeter of the plant, and wrapping burlap around the stakes. Plants can also be wrapped directly with burlap, but extra care must be taken to remove the wrapping promptly when temperatures warm up again.
Spraying the foliage of your vulnerable plants with WiltPruf, an anti-transpirant made from natural plant resins, is another good option. Watering your plants well before a cold spell will also help stave off winter burn, by providing liquid water to replenish moisture lost through transpiration.
Plants in Containers:
Plants in containers require special consideration. Although a plant’s roots may be perfectly well adapted to surviving in the soil when the air temperature reaches the edge of the hardiness zone that it is suited to, soil in the container is subject to more severe temperature fluctuations. For this reason, we generally recommend that perennials and shrubs in containers be at least one or two zones hardier than your zone to survive the winter.
For protection of tender plants in containers, in addition to protecting foliage with a crop cover, there are two main options to protect the roots:
- Bring them closer to your house and insulate them by wrapping the pots well. Any material with lots of air spaces is great for this; even use bubble wrap for extra insulation (provided the plastic is not touching the plant).
- Dig a hole in the ground (preferably in a protected area), put your plant and its pot in the hole, and mulch well.
Common Plants in our Area that may require protection:
- Hardy Banana
- Windmill Palms
- Dracaena Palms
- New Zealand Flax
- Cedar & Evergreen Hedges
- Evergreen Magnolia
- Spring Flowering Annuals
If you have tender plants in your garden, here are some other quick tips to protect them:
- Mulch the roots with 2-4” of bark mulch, coco coir (e.g. Mega Mulch), leaves, or straw. This helps trap heat released from the soil. If you have tender bulbs planted, this is especially important to ensure their survival.
- Crop cover (thick insulating fabric) laid out over plants will help trap heat and keep the foliage a few degrees warmer than the surrounding air. It also prevents moisture loss through the leaves, while still allowing penetration of some light and water.
- A wind break structure erected around your vulnerable plants will prevent the wind from drawing moisture from the leaves (the cause of winter burn). Simply place several stakes around the perimeter of your plant, and wrap burlap around them up to the full height of the plant.
- Water your plants well before a cold spell. Water frozen in the soil is unavailable to the plant, so providing liquid water will replenish moisture lost through from leaves, and mitigate winter burn damage.
- Protect plants in containers by either bringing them close to the house and wrap the pots with an insulating material (generous layers of blankets, burlap, or even bubble wrap) . Alternatively, false plant containers in a hole in the ground and mulch thoroughly. In both cases, drape a crop cover over the foliage so it is protected as well. If you have exceptionally tender plants in containers, bring them either indoors, or in an unheated garage.
In the Lower Mainland, we really are spoiled with such a beautiful, mild climate. Expanding our choices of plants to those that may be slightly outside of their comfort zone may require a bit of extra work, but it’s worth it for the richness and beauty they bring to our yards and lives. If you do decide that you prefer some lower-maintenance plants, there are still myriad choices available to you, in every size, texture, and colour.
For help finding the right plant or deciding how to protect the ones you already have, visit one of our GardenWorks locations and our experts will be happy to give you more guidance!
Written by: Chantel Taylor