Invasive Plants

Toronto Star column – published April 26, 2014

Invasion

There has been a lot of discussion about ‘invasives’ in horticultural circles over recent years.  These are the so called ‘bad guys’ that you don’t want to plant in your garden, or at the very least, you don’t want to plant anywhere near natural areas like a ravine, conservation area or park.

You might ask, “What are invasive plants and what are the alternatives to planting some of my favourites?”

The answers, happily, are in the small publication, Grow Me Instead, published in cooperation with the Ontario Ministry of Natural Resources, Toronto and Region Conservation, and Landscape Ontario, our industry trade association.  You can pick up a copy at Ministry offices or go online and download it for free at www.ontarioinvasiveplants.ca

Here is the hard part: many of the invasive plants referred to in the guide may be among your favourites.  That is certainly true for me.  When I was in my teens and early 20’s I sold more than my share of truck loads of Norway Maples, grown on our Weall and Cullen farms and distributed through our outlets in the GTA for decades.  Ooops!  While I feel a slight tinge of guilt for the exercise, there is redemption.  For one, a Norway Maple, arguably, is only invasive when the seeds of it are near a naturalized area.  Outside of the ‘restricted zone’ it makes for a fine urban tree: a fast growing, pollution tolerant tree producing thick green leaves, cooling shade and black patches on its leaves come late summer [aka ‘Maple Blotch’ – ok, it isn’t perfect].

Another of my favourite plants and one species that I can be held responsible for selling like Chiclets in the 70’s and 80’s is English Ivy.  Ditto the Norway Maple story.  Only this one is disease resistant and beautiful.

The good news is that there are alternatives to the invasive plants that we have planted in quantity in the past and they are attractive, accessible from local retailers and have their own list of redeeming features.

The aforementioned Norway Maple, for example, can be suitably replaced with Sugar Maple [my first choice], Silver [Soft] Maple, Freeman Maple, Hackberry [Celtis occidentalis] and Serviceberry.  The Guide provides details that will help you determine your best choice, given your personal preference, fall colour and the site location of your tree.

English Ivy is classed among other invasives like Goutweed [Aegapodium] and perennial Periwinkle [Vinca minor].  The alternatives include Wild Strawberry [a bit invasive in its own right where a weak lawn is concerned], Wild Ginger [especially in a shady garden setting], Mayapple [another shade lover], Bunchweed [don’t let the word ‘weed’ mislead you] and Wintergreen [gaultheria].  The beauty of the listed alternatives is that they are native and winter hardy in your growing zone.

Another invasive plant is the Russian Olive, a fast growing shrub that can get as a large as a small tree [about 8 meters or so].  This plant suffered a great deal during the December Ice Storm as the branches of it are brittle.  It has nasty thorns that are twice as long as your mother’s darning needle.  Ouch.  Consider planting a native Dogwood, Witch Hazel [great fun to watch it become the first of all shrubs to flower in the garden late each winter], Common Ninebark and Fragrant Sumac.

Other Invasives

Some of the plants that are listed in the guide as invasive surprised even me, and I am supposed to know about these things, so they tell me.  Japanese Barberry, Multi Flora Rose, Japanese Honeysuckle, Oriental Bittersweet and the well used ornamental grass Miscanthus are all listed.  Again, the guide does us a great service by providing us with alternatives that, for the most part, I agree with and you will find at most full-service garden centres in your community.

I cannot, for the life of me, understand why they recommend Chokecherry [Prunus virginiana] and Alternate-Leaf Dogwood [Cornus alternafolia] as both of these are a pain on my farm where they grow naturally in the wind row.  I have spent a moderate amount of time and risked life and limb applying my chain saw skills to the chokecherry.  Its only saving grace is that it burns nicely in my fireplace.

Alas, the publication of a guide like Grow Me Instead is not an attempt to win a popularity contest.  It is, however, another important signal of how the business of gardening is changing.  People like me, who are used to their English Ivy and Norway Maples may be reluctant to change our planting choices, but the truth is that it is the new generation of gardeners, the ones in their 20’s, 30’s and early 40’s, who will lead the way on this and they are keenly interested in doing the environmentally right thing.  The rest of us can follow along or get out of the way.

If you are among those who want to learn more, I have the following advice for you:

– Purchase non-invasive or native plants from reputable suppliers.  A list of nurseries specializing in native plants can be found at www.nanps.org.  Fern Ridge Landscaping in Milton provides consultations on native plant landscaping and installations.  The founder, Sean James, had a hand in the writing of Grow Me Instead.

– Do not remove plants form natural areas: many are rare native plants or even invasive.  Transplanting from the wild often results in failure in the garden.  In my experience nursery grown native plants perform much better in the home garden as they are grown in containers for that purpose.

– Make sure that the native plants that you do purchase have been sourced locally [within a couple hundred kilometers, preferably].  It is not uncommon, for example, to buy a ‘wildflower’ seed mix with seed in it that has been sourced from California or worse, from overseas.

– Avoid spreading the roots and seeds of invasive plants by disposing of them through your local municipality or in your backyard compost.  Do not dump yard waste in nearby natural areas including the ravine or public green space that your yard may back onto.

As Tony DiGiovanni, the executive director of Landscape Ontario says, “It is hard to believe that some of our favourite plants can cause economic and environmental damage.  They can.  Some species can cause serious problems if planted near natural areas where they have a tendency to out-compete native species and alter local environmental conditions.”

As you wade into another planting season, anxious to make your garden the best looking and most productive that it has ever been, I urge you to advance with some caution and be sure that the practices that you employ out there fit with the larger community of wildlife, both plant and animal.  Enhanced biodiversity will benefit greatly for your efforts.