GARDENING WITH NATURE

Article by Sigrie Kendrick

Think outside the box when prepping for winter

As gardeners, let’s remember to switch up the traditional garden tasks and think in a different direction: perhaps a more environmentally friendly one, that also provides us with more winter garden interest.

For instance, fall is the time of year when ornamental grasses shine. Many are in bloom and at the peak of their beauty.

What poet within us wouldn’t be charmed by the gentle way their graceful seed heads sway in the breeze and dance on the long stalks they’ve been growing all season? Grasses really add movement to your garden—unless you chop them down prematurely.

I recently had the opportunity to consider the importance ornamental grasses hold in our gardens as I cut down literally hundreds of Calamagrostis x acutiflora ‘Karl Foerster’, commonly known as Feather Reed grass, at a client’s property.

So often clients want their grasses razed to the ground before the onset of winter as they
perceive the standing grasses to be “messy” rather than graceful.

Often, land care providers such as landscapers are all too happy to oblige as that means one less task facing them in the spring.

Instead of this perverse desire to tidy in the fall why not take into consideration all the benefits of leaving ornamental grasses over the winter?

What about ecology?

From an ecological standpoint there also are many reasons to leave your ornamental grasses and your perennials standing over the winter. They provide needed habitat for birds and a myriad of other wildlife, as well as for beneficial insects to overwinter.

The seed heads of ornamental grasses and also annuals and perennials which have gone to seed, provide food for birds, who have to forage widely during the colder months, just to survive. They also provide great erosion prevention and slope stability, especially where wildfire has run through the previous season.

The time to shear your ornamental grasses is when you begin to see new growth at the base sometime in spring. Then, don’t toss out the cut grass. Instead, find a spot in your yard where it will be out of your way, but will provide valuable habitat for beneficial insects.

Perennials can also be pruned in early spring, when new growth begins to be visible, while annuals can be pulled out as soon as the ground softens in late winter or early spring.

Remember too that the fallen leaves from deciduous trees should also be left where they fall, rather than being neatly raked up and composted elsewhere in the fall. Those rotting leaves are like gold to a gardener and they provide habitat for insects and wildlife while they decompose over winter.

They also suppress weed growth and protect the roots of perennials over winter and what’s left can be gently dug into the soil come spring.

So, leave the leaves, don’t mow down the grasses and allow perennials and annuals to go to seed (unless they tend to be invasive!)

GARDENING WITH NATURE

Extreme weather taking its toll on gardens

For instance, do not prune your plants in the heat.
Periods of intense heat are stressful for your plants, and pruning, especially thinning, will only serve to
increase this stress.

Removing leaf matter increases the effects of heat on the remaining vegetation, decreasing the humidity
and therefore forcing the remaining leaves to transpire more to cool the plant.

This often has disastrous results.

Another no-no in periods of extreme heat is fertilizing your plants.

Try to make sure your garden has the nutrients necessary for plant health prior to any spike in
temperature.

Adding fertilizer is almost akin to adding salt to your soil as fertilizer essentially makes it harder for your
plants to access the water in the soil. High concentrations of nutrients actually reverse osmosis, the process by which a plant is able to absorb water from the soil. The osmotic pressure is reversed so that the pressure outside the roots becomes greater than inside, making plants unable to access moisture from the soil and they actually lose water back into the surrounding ground.

Planting in the heat of summer is not ideal

Out of necessity, the landscape industry must continue to plant throughout the hottest summer weather but this is far from an ideal situation.

If at all possible delay your planting to the coolness of shorter days in late summer when the ambient air
temperature has decreased but the warm soil necessary for strong root establishment exists.

If you must plant in high heat, at least offer supplemental shade for new plantings by using shade cloth or, in a pinch, an old white sheet.

This shade is even more vital if you are planting in an area of ‘high albedo’. High albedo environments occur where there is a great deal of reflection such as found in a rock garden. This reflective sunlight will damage young plants that can not transpire enough in the high heat to cool their leaves and almost immediately begin exhibiting heat stress.

Unusual snowfall in early November 2022 landed on trees whos leaves had not had time to drop yet

At the other end of the spectrum, severe winter weather caused considerable havoc in Okanagan gardens, as well as in commercial orchards and vineyards.

The weather we have experienced over the last two years has had severe repercussions for our trees, shrubs, perennials, vines, and ornamental grasses.

In the Okanagan Xeriscape Association’s demonstration garden, we saw the complete loss of several Lavenders and Penstemon and extensive injury to several of our trees from the 2022/2023 winter. The Parrotia persica, the Robinia pseudoacacia ‘Twisty Baby’ and the Koelreuteria all have suffered winter damage, and the latter has had to be removed. It’s a heart-breaking loss.

I have heard other Master Gardeners around the valley sharing similar stories of witnessing first-hand deaths of these plants as well as Buddleia, Hybiscus syriacus and various ornamental grasses.

I know that the long warm fall followed by the extreme and abrupt cold experienced in the beginning of November was to blame for much of the damage, similar to your forgotten frozen water bottle exploding, but I wanted to know more. It was hard to ignore that many of our trees held their browned leaves through the winter, never having the chance to drop them as they normally would, with last fall’s sudden lurch from summer into winter.

I consulted with plant pathologist Robert Hogue of Pegasus Horticultural to gain a better understanding of the physiological process which had wreaked such havoc.

Robert explained that it all actually began with the Heat Dome of 2021 when plant tissue was damaged by the extreme heat, registering into the mid-40s.

Like people, plants go into a low-energy state in extreme heat. In survival mode plants do not process as much carbon dioxide, leading to less carbohydrates moving into the roots. This lack of carbon dioxide means the roots receive less sugars which compromises the ability of the roots to absorb the necessary water and nutrients from the soil.

This in turn leads to root death and with the death of large woody roots comes the death of the organism as a whole. This root death also occurred last fall with the abrupt arrival of winter when the roots were still actively growing.

As Robert explained, ‘The abrupt cessation of metabolic activity in the above-ground plant parts meant there was not enough nutrient flow to the roots to complete the suberization process’.

Suberization is the process by which the root walls harden off into corky tissue similar to a callus over a wound. These weakened feeder roots act as an entry for many root pathogens such as Fusarium, Pythium, and Verticillium.

The damage can be immediate, as seen this spring when the plant abruptly died after a seemingly normal leaf-out; but in other cases there will be a slow but inevitable death.

Robert has done extensive research on the hardiness of plant life in the valley and has come to the conclusion that we simply can not rely on traditional plant hardiness ratings in our changing climate.

Gardening with Nature

Article by Sigrie Kendrick

Leave the leaves!

Don’t stress over fall garden clean-up.  Just leave the leaves on the ground where they fall.

I have to question why, as gardeners, we are so obsessed with the big fall clean-up, including raking or blowing all the fallen leaves into piles, shoveling them into plastic bags and sending them off to the landfill—or even to be composted centrally.

It’s a tradition we really should reconsider.

In fact, this is counter-productive behaviour. Instead, we would like to educate everyone about the many benefits of leaving the leaves where they fall in the fall.

Let us mimic what occurs naturally, in contrast to our need to clean, control and manipulate our natural environment.

There’s a reason for everything in nature.

Leaves are nature’s nutrient recyclers.

For example, with the shorter days of light in the fall, the leaves of deciduous trees and shrubs fall to the ground and act as a mulch, which suppresses weeds, protects the roots of perennials from the winter cold and feeds the soil as they decay.

Their decomposition creates rich organic matter in the soil that helps your garden become lush and beautiful.

Leaving your tree, shrub, and perennial ‘mess’ in place over winter also provides a source of food and sanctuary for a whole host of small mammals, birds, and insects.

Sigrie Kendrick is a Master Gardener and Executive-Director of the Okanagan Xeriscape Association. She can be reached at 778-363-8360 or by email at exec_dir@okanaganxeriscape.org.