Why has the Switchback become overgrown with invasive species, and could it be repaired to become a showcase for native species and pollinators?

The Chorley Switchback is a wide paved zig-zag path. At the top, there is Rosedale, with its leafy lanes and large historic houses. At the bottom are the Toronto ravine system and the Don Valley Brickworks Park, a City of Toronto flagship natural environment park that is considered a model for urban ecosystem planning because of its extensive landscape restoration and re-naturalization.

The construction of the Switchback was controversial, as local residents felt that the City’s proposed path was too massive, with some solid stone block walls, and had too many switchback turns that would create a longer route than the existing natural steep path. The City of Toronto needed to create a path that met accessibility guidelines to accommodate wheelchairs and strollers, and it wanted a solid construction that would last for years with minimal maintenance. Eventually, a compromise was reached, and a modified version of the Switchback was built at a cost of over $1 million. A natural path through the nearby woods was also improved and re-routed.

The Switchback nearly divided us. It was a considerable investment, and although most would now agree that it is an enhancement to the community and access. Why has the Switchback become overgrown with invasive species, and could it be repaired to become a showcase for native species and pollinators?

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After construction, the site was planted with a variety of native trees and shrubs. Urban Forest Associates, a leading-edge company working in private and public spheres, was contracted to supervise the planting. Members of the local community eagerly joined in the effort to populate the slope with tree saplings, shrubs and native herbaceous species.

Cottonwood, maple, white pine and bur oaks have now become established. Below them are native shrubs such as serviceberry, wild rose and purple-flowering raspberries.

But beneath the trees and shrubs, there is an awful mess of invasive species, such as burdock, dog-strangling vine and garlic mustard.

The City of Toronto’s Turfgrass and Prohibited Plants Bylaw requires the owners or occupants of private properties to keep their land free of Canada thistle, DSV, buckthorn and garlic mustard. However, the City is allowing these plants to grow on its own property.

Invasive species threaten to take over the whole site and spread far and wide into the ravine, the Brickworks, and all of our properties. Our shoes, clothing, dogs and the wind dissipate the seeds everywhere.

Some local residents would like to do something about the situation and are prepared to devote their own time, effort and resources to restoring the natural beauty and native fauna of the area, but so far, they have been rebuffed by the City. The North Rosedale Residents Association (NRRA) asked for permission to organize a community event to pull garlic mustard from the site, but the City was not receptive to the idea, ostensibly due to concern with the site’s slope. The y said that the task would be handled by City staff. Toronto Nature Stewards, a volunteer conservation group that already stewards over thirty pieces of public land, asked to be allowed to add Chorley Park as an additional site but was told that it was not only an ESA (environmentally significant area), but that City Staff “had it covered.” This ESA designation was questionable, even before several years of heavy construction work that degraded the site.

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What does the Switchback look like now?

The pictures illustrate the problem. The site is disfigured by massive burdock leaves that will go on to produce large and ugly seed heads. In late spring, the white flowers of garlic mustard appear. As they die out and spread their seeds, a dog-strangling vine (DSV) appears and in some places, takes over completely, leaving no room at all for any other plant to grow.

To be fair, the City has made some token efforts to maintain the Switchback. In late May, they weed-whacked the side of the path, but this was mainly a cosmetic effort that only extended a few out from the path, leaving large areas completely untouched. Garlic mustard seedheads were left in place rather than being removed from the site.

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What are the invasive species that are growing in the Switchback, and why are they a problem?

	Dog-strangling Vine or DSV A thin plant with alternate long and pointed leaves that can grow in full sun or deep shade. Once it is about a metre tall, it twists around any tall structures available, including other dog-strangling vines. It has small dark flowers in June, which produce seedheads and distribute thousands of little dandelion or milkweed-type seeds on little parachutes. It confuses monarch butterflies, as it is a milkweed. If butterflies lay eggs on DSV, the larvae will not eat the plant and will starve to death. DSV can produce large areas of monoculture where no other plant has any room to grow. Also, it can toxify the soil and make it more difficult for other plants to grow. It can be dug out with its roots, but this takes a time commitment and a lot of effort that the City cannot provide at present.
	Garlic Mustard Garlic Mustard (Alliaria petiolata) is an adaptable, aggressive, biennial (2-year life cycle) herbaceous plant in the mustard (Brassicaceae) family, which is sometimes called Hedge Garlic or Sauce Alone. Garlic Mustard is native to Europe and can be found from England to Italy. It was introduced to North America as a food source and was used as herbal medicine by settlers in the late 1800s. It has escaped cultivation to become a serious invader in Ontario’s temperate forests, agricultural fencerows, public rights of ways and residential lands. The best time to remove garlic mustard is in May and June, when they have expended resources to produce flowers, but before the seeds become viable. It is easy to pull out as its roots are not very deep.
	Burdock Burdock is an invasive biennial plant that spreads quickly and easily, allowing it to grow in place of many beneficial native plants. One plant can produce up to 15,000 seeds which readily attach to materials or animals that brush up against them. Seeds can survive one to three years and sometimes longer. Birds (such as the Kinglet) and bats can get caught by the burs and die. The plant can be dug up in the spring, with its deep tap root, or the leaves can be chopped off in the summer, preventing it from forming seeds.

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What needs to be done?

So many invasive species are rampant in Toronto’s parks and ravines, threatening biodiversity and ravine health, that it is necessary to prioritize key areas. Highly visible sites in busy locations are more important than hidden and distant locations. Sites that would attract volunteers are higher priorities than sites that cannot. Sites that neighbour other sensitive areas that need to be protected, such as the Ravine system and the Brickworks, also deserve priority. The Chorley Switchback meets all these criteria.

In three years, the Switchback has evolved from a potentially beautiful naturalized site into a neglected eyesore of neglect.

Private homeowners can be prosecuted for allowing noxious weeds to grow on their property according to the TORONTO MUNICIPAL CODE CHAPTER 489, TURFGRASS AND PROHIBITED PLANTS bylaw.

Surely, therefore, private citizens should be allowed, encouraged and supported in removing noxious weeds from City property.
The City has an obligation to accept donations of time and effort from volunteers.

The City of Toronto’s Ravine Strategy states that:

“The care and enhancement of Toronto’s ravines and the success of the Ravine Strategy require the City, individuals and organizations to work together in meaningful and sustainable ways. Partnerships will support expanding opportunities for volunteer ecological stewardship activities, ensuring good communication and implementing best practices for managing ravine parklands across municipal boundaries.”

In addition to the NRRA and Toronto Nature Stewards (TNS), the University of Toronto’s Institute of Forestry and Conservation, other organizations such as Don’t Mess With The Don would likely be interested in being involved in a program to remove invasive species and replant native species in the Chorley switchback, making it a showcase for native plants, pollinators and community nature conservation.

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