It is not uncommon for “plant folk” to push the boundaries of hardiness zones to the absolute possible limits, then take a few more steps. I am guilty as charged on this count as most frequently I disregard hardiness under the philosophy that want and desire trump sensibility. If you are a gardener like this, there are a few minor adjustments that need to be applied in order to secure hardiness. An age-old discussion within the green industry from the professional to homeowners, is the winter protection of evergreen shrubs. Naturally the decision to cover up or not depends on which region of the country the landscape is in and the plants themselves. Many gardeners wrap all the evergreen shrubs in their landscape as soon as the temperature drops while others do nothing at all. Which is correct or is there a correct?
Consider that the burlap shrouds adorning many evergreens is neither a fashion statement nor a protection against the cold. The purpose of a burlap cover is to protect the plant from the sun, yes the sun. The evergreen will be in dormancy once the ground has sufficiently frozen, however once the sun grows in strength, the foliage may start to function. The all to common sun scald or sun damage that appears on many shrubs is not because the weather has been unusually cold but rather bright and sunny. Moisture that is stored in the leaves will be used up in no time and with the plant’s inability to draw moisture from the frozen soil, the brown desiccation is the result. Understanding this significant point, if a burlap or fabric cover is considered, it can be applied once the soil is frozen. Under no circumstances is any form of plastic covering acceptable! Plastics and fabrics that do not breathe will heat up the air spaces within when the sun is shining. This unusual warmth, even a few degrees, may trigger the plant to activate. Wind barriers away from the dormant plants can be fabricated using plastic just not the winter covering.
Watering the evergreen shrubs heavily before freeze up is also an excellent final task before the hose is drained for the winter. This reservoir of moisture of course will freeze when the soil does and will remain so until spring thaw. The moisture that is so desperately needed first thing in the spring as the sunlight strengthens, will be available immediately. The combination of a burlap or fabric sun shield and the water reservoir may help extend the limits of your hardiness zone.
Hybrid Tea, floribunda and polyantha roses require some attention as well as winter temperatures drop. These roses have been grafted onto a durable, hardy rootstalk well before they are offered for sale. The conspicuous “knuckle” or graft union is the result of this union and also the most vulnerable part of the plant. In regions where the temperatures drop well in the -20C, roses demand winter protection. One of the most reliable ways to ensure overwintering is simply hill soil up around the rose as high up the stems as you can. Some gardeners in colder climates will also form a collar of cardboard or any other material and place that around each rose plant. Some will fill the collar with dried leaves if they haven’t composted them yet while others will fill the collar with dry peat moss, wood shavings and even fibreglass insultation. The Styrofoam canisters one finds in the late fall in garden centres are less than ideal in my opinion. Should you choose to use this method, cut the bottom out of the container and use it as a collar. Keep in mind that stems that are left above the protected area will freeze and require removal in the spring. Many gardeners will prune their roses back in the late fall, early winter so that all stems can be protected from the extremes. Roses are un-hilled, cleaned up and pruned in the spring, that process will be dealt with closer to the appropriate season.
November 26th, 2017