Invasive Perennials — Buyer Beware!

Invasive Perennials — Buyer Beware! - theHumm June 2021

By David Hinks

I find that gardeners who choose perennial flowers to grace their yards and gardens face a bit of a dilemma. One the one hand gardeners want plants that will thrive; on the other hand they want plants that will be well behaved. Many people go into gardening with perennials believing that it will be effortless — put in the right plants and your new perennial border will be maintenance-free.

Not completely true! I find that the essence of gardening is really our desire to “shape unruly nature” to exert human control. Even that somewhat-wild Country Garden requires a lot of work — weeding, dividing perennials, dealing with pests and disease, and replacing plants that did not thrive as promised.

What is your gardening philosophy? How much “wild” can you live with?

Of paramount importance when creating a perennial border is the elimination of weeds. I always stress the importance of knowing what types of weeds you are digging out when you are preparing your planting beds. For example, dandelions have a long tap root — if you are able to get the whole root the plant will not come back; however, any piece of root left in the ground will regenerate. Perennial grasses are difficult to eliminate as they have long horizontal roots that may stretch half a metre or more. These are best removed with a spading fork. A rototiller will break those roots into little pieces, every one of which will send up a new plant.

There are many ways to introduce unwelcome intruders into the garden. Beware of special deals on a cubic yard of topsoil delivered right to your driveway. I had the occasion a few years ago to check out a large-scale landscaping project. What I saw horrified me! Two new large perennial beds, very professionally hard-scaped with beautiful stone, had been filled with soil the previous fall. Instead of a beautiful loamy planting bed I was astonished to observe a veritable witch’s brew of six or seven of the most invasive weeds that a gardener can imagine. Imagine if you will a cocktail of burdock, sow thistle, Canada thistle, Japanese Knotweed, quack grass, Japanese lantern and colt’s foot — the only plants missing were bindweed and goutweed! I am a firm believer in dealing with local reputable businesses that I can trust. The price may be somewhat higher, but most of the time you “get what you pay for”.

How do invasive plants get here? The reality is that the primary vehicle for the spread of many invasive plants is the automobile — bringing them home from plant sales! Gardeners plant many invasive plants because they are very attractive. Japanese Knotweed, for example, was introduced to North America as a horticultural plant in the late 19th century and was widely planted as an ornamental, for the purposes of erosion control and as forage for livestock. And it can be a very attractive structural plant, resembling bamboo, but this is one tough hombre to confine.

Goutweed is often seen in perennial gardens — I have found it the absolute worst thug to eliminate in a garden. The irony is that people still continue to plant it and offer it to other gardeners. There are two forms: a variegated version and the all-green one. If tightly controlled, for example, between a house foundation and a sidewalk, it can be quite attractive, but it has to be watched carefully as it spreads underground.

Once established, goutweed is nearly impossible to eradicate. The smallest piece of rhizome left in the ground will quickly form a sturdy new plant. The primary vector for dispersal to new areas is human plantings as an ornamental, medicinal or vegetable plant, as well as by accidentally spreading rhizomes by dumping of garden waste. It spreads rapidly under favourable growing conditions. We have huge beds of goutweed at the Mill of Kintail.

Attempts to control goutweed in a garden with landscape cloth, bark mulch, and hand weeding are largely unsuccessful. Hand pulling, raking, and digging followed by monitoring to control goutweed may be effective – I have found the best approach to be a large cover of heavy black plastic in place for a year or more. But the best control is to not plant it in the first place. If anyone offers it to you — run!

Creeping bellflower is another thug that comes into gardens disguised as an attractive perennial plant. It is very attractive this time of year and in fact was introduced from Europe as a garden flower. It is commonly seen around town in gardens and in areas that may once have been tended gardens.

I have found it very difficult to eliminate from places I don’t want it. Any piece of that white creeping root (rhizome) or the tubers left in the soil will send up a new plant. The roots need to be dug up carefully and discarded.

Noted garden writer Larry Hodgson ranks this plant very high on his list of invasive plants to avoid, right up there with goutweed and Japanese knotweed. You have been warned! I highly recommend his book Perennials for Every Purpose as a great reference before adding new plants to your garden.

Frank Sammut —Fine Wood Working - theHumm June 2021

By Sally Hansen

Art… and Soul

Kokopelli Custom Woodworking is Frank Sammut’s celebration of the natural beauty and wonder encapsulated in the trees that fall on his 87 acres of bush lot near Maberly. His lifelong fondness for working with his hands has culminated in a passion for creating one-of-a-kind pieces of furniture that showcase nature’s beauty. Wood speaks to him. And he creates poetry in response.

Frank’s artistic tables and benches are as much sculptures as the......

Invasive Perennials — Buyer Beware! - theHumm June 2021