So, you ask, what kind of weirdo would start a gardening/design column on the cusp of December? Well there’s still stuff to do, I say, and I hope we can have a bit of fun doing some planning over the winter.
After all, the days will start to get longer in just a few weeks, and I hope to have you speaking Latin before spring arrives, for one thing.
At this time of year, we need to consider protecting certain plants and shrubs that may need our help. Evergreens, which include most conifers and many broad-leaf species, may be particularly stressed by drying winter winds and more exposure to sunlight with the leafy deciduous canopy gone.
All plants transpire, which is to say they lose moisture through their leaves or needles. It is this miracle (or cosmic accident, depending on your point of view) that makes trees effective air conditioners – literally. It is not just the fact that trees shade us and make us feel cooler by blocking the sun’s radiant energy; the process of evaporation actually uses heat energy in the transfer from water to water vapour, hence the air is cooled.
On a milder winter day, when the ground is frozen and the roots are unable to take up water, evergreens will still transpire, and, over time, may dehydrate to the point that they are injured or die. You’ve seen brown tips on cedars and ‘burned’ leaves on boxwoods and rhododendrons in the spring, right? These may well recover, but can be set back and weakened, and a weakened plant is more likely to be a victim of pests and disease.
A young evergreen shrub or tree planted this year may not have had time to develop its root system to the point that it is taking up water efficiently, and you may want to consider protecting it for its first winter by providing a burlap screen to cut the wind and the harsh sunlight. You can simply wrap a vertical shape like an emerald cedar, or use stakes to define a burlap perimeter or tent around a rhodo, or create a burlap fence to shelter a young cedar or boxwood hedge from the prevailing winter winds.
If you are wrapping the tree, be sure to use burlap as opposed to plastic or house-wrap, as the leaves need to breathe too. Your garden centre will have the right stuff. Thoroughly watering newly-established evergreens as late as possible in the season will help mitigate moisture loss through transpiration.
Young deciduous trees with thin bark may also suffer in the winter, but for a different reason: Most trees thrive in a mixed forest community, where they provide shelter for one another from the wind and the sun, cast their leaves on the forest floor to enrich the soil, and support a diversity of wildlife, including insect predators, to protect one another from pests.
You can see we sure ask a lot by plunking a single tree in the centre of a lawn in the landscape. Alternate warming and freezing of exposed bark in the winter – especially on those days where the warm afternoon sun is followed by a sudden temperature drop - can often split the bark, allowing an entry point for pests and disease as spring approaches. This is often called ‘south-west injury’ for obvious reasons.
Tree wraps are available from your garden centre which will help reduce the extreme variations in bark heating and cooling, but remember to take these off in the spring, as they may shelter boring pest larvae which would otherwise get picked off by the birds.
Well, that’s it for now. If you still have a big pile of leaves that you don’t know what to do with, let me know and I’ll send you my leaf compost recipe.
We’ll talk again soon.
Thomas Dean of Black Sheep Design in Meaford, is a graduate of the University of Guelph in Horticulture and Landscape Design. Thomas will be a regular contributor of gardening and horticulture articles for The Meaford Independent.
You can contact Thomas by emailing: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
