Led by Christina Read and Diana Wilson, Toronto Region Conservation Authority (TRCA)
This note is based on the information shared by Christina and Diana on a walk through the Glen Stewart Ravine on June 8th, starting at Beech Ave and travelling south to Glen Manor Dr. E. The two leaders identified many of the native and invasive species that were found here in June. This blog is not directly quoted but is an adaptation of the information shared on the walk. Any omissions or errors can be attributed to the editor.
What is a watershed? It is an area of land that is drained by a body of water, a river or lake. The walk starts off in the waterfront watershed. If you are wondering where this stream goes along with all the rain that comes down here, it drains into Lake Ontario.
It is important that we carefully manage areas that can reduce the impact we have on the environment, particularly areas like this. This area is environmentally significant. It is different than the other areas around here. Nearby there is a lot of pavement, construction and houses. It is difficult for water to drain through the soil when the space is so built up and covered with our urban landscape. Whereas, in the ravine, you can see opportunities for the water to be filtered before it goes into Lake Ontario.
Ravines cover about 17% of Toronto’s urban landscape. When the glaciers melted about 10,000 years ago, the streams and rivers formed from the melting glaciers eroded the glacial deposits, creating the ravines we have today.
The land now known as Glen Stewart Ravine was originally owned as a homestead named “Glen Stewart” by Rev. William Stewart Darling in 1872. In 1900, it was sold to A. E. Ames, a stockbroker. The estate at one time included a 9-hole golf course. Then in 1931, 4.6 hectares were donated to the City of Toronto. Later the City purchased about four more hectares. It is a large piece of “unused” land, considering where it is in the City of Toronto.
It was designated an Environmentally Significant Area in 1982 by the TRCA. And in 1992 it was dubbed an ESA by the City of Toronto using different standards. Then again, in 2007 they revisited it with different criteria and it still is environmentally significant for three reasons. It has some rare species, it is very diverse, and it provides many ecological functions that extend beyond this park. Primarily, it provides shelter and food for migratory birds on their trip south. About 22 types of wildlife have been identified in this area, mostly different species of birds.
Red Oak – A biodiversity hot spot
Around the time when the ravines were formed by the receding glaciers, there was an ancient lake, Lake Iroquois. Around the edge of this Lake grew a tree species, called a ridge species as it tends to grow on top of ridges. Good examples of it can be seen here. Most common in this wooded area is the red oak tree species. Similar to the red oak is the black oak. Examples of black oak can be found in High Park; in the N.E. corner is the Black Oak Savannah.
To find a red oak you might have to look very high up in the canopy or you can look down at leaves on the ground. The red oak leaves take a long time to decompose. After the winter they are still intact. Its leaves are classic oak leaves. Red and black oak leaves have points on them and are quite large. Red oaks have grey bark with ridges or dark rivulets, in the trunk. And, of course, in the fall you can find acorns below an oak tree.
White oaks are also a magnificent species. White oaks are a specimen species, which needs an open habitat. A white oak’s canopy can be as wide as the tree is tall if it has enough space. It is a humungous tree. possibly growing to an older age than a red oak, as it grows more slowly. It is not used in landscaping as much as the red oak for these reasons. In a forest it would grow tall rather than wide. It provides almost as much in the way of habitat as the red oak.
White oaks can be confused with English oaks. They have similar leaves, being rounded. The English oak is a non-native species and grows in a columnar shape.
Other shrubs and trees in the Glen Stewart Ravine
The next species that can be identified in the late spring by its flowers as well as its leaves, is the alternate-leafed dogwood. It is quite prevalent in the ravine.
Norway and Manitoba maples also grow here. They are sometimes called weed maples – they can grow in tiny little cracks. They create extremely dense shade so grass or other plants cannot survive below them. Groundcover, under the oaks and native maples helps prevent erosion by absorbing runoff rainwater and holding onto the soil. Whereas, Norway and Manitoba maples, by inhibiting the growth of groundcover, can exacerbate erosion in the ravine.
As you move from the ridge down into the ravine, the species will change to wetland and ravine trees. One plant that signifies that change is the flowering raspberry. This has a beautiful pink flower. It produces raspberries, but these may not be edible.
Next, you can see a red maple. Their leaves are less pointy than the maple leaf you see on the Canadian flag, they are simple and round.
Silver maple leaves have deeper lobes and points.
Next, there is an American Beech Tree. Its trunk resembles an elephant’s leg. It has smooth grey bark. They often grow in low ravine lands, or near rivers as they prefer damp areas. American Beech are not usually on private urban property but are found in ravines and forests. Copper beech is sometimes used decoratively.
At the bottom of the ravine, runs Ames creek. It is a spring-fed stream. The spring is located near the beginning of our walk at Beech Avenue. And this is one of Toronto’s lost rivers. Some are above ground and some disappear below ground. They have been buried so the City could grow around and over them. This creek once extended south to Lake Ontario, but now, part of it has been covered up. Once it heads underground, it still continues for quite some distance.If you walk through the park south of the ravine you can hear the water rushing below the ground.
Although birds were not identified on this walk, they made their presence known with their songs. And a family of mallard ducks were spotted in the creek.
During the previous week, Christina and Diana, had noticed an infestation of cankerworms. These are also called inchworms.
There were so many they were literally dropping from the trees. They defoliate the trees creating a lacy effect in the tree canopy. All tree types were affected, but particularly the oak trees. Mature trees can survive such an infestation, but younger trees are more susceptible to harm. And, if the infestation repeats year after year, these worms can seriously harm even the larger trees.
Yellow birch trees were identified on the hillside and then willows.
One fascinating fact about willows is that the can regrow themselves. When branches fall into the river and flow downstream, they can regrow in a new location. They are sometimes used as living fences. You can see an example of this at Evergreen Brickworks in the Children’s Garden. The willows create shade in the summer then lose their leaves in the winter.
Compacted soil = erosion
Christina observed that on the west side of the path the slopes were eroding and the roots of oak trees were exposed. She said, “A lot of you have probably tripped over some of the roots of the red oaks that are exposed.” For many tree species the roots grow in the top 12 to 18” of soil. Oaks also have a long taproot that can extend down to the ground water. Maples sometimes extend their roots horizontally to obtain sufficient water.
One problem can occur when people and pets wander off the main trails. Walking on the soil over the roots compacts the soil, turning it into something more like concrete. Rainwater then runs off instead of percolating down through the soil. The runoff goes straight into the creek, taking with it contaminants and soil, impacting water quality.
The City has implemented a number of strategies to help reduce these impacts from erosion. This spring, Urban Forestry planted over 800 plants, including oak, maple and witch hazel. The roots of the plants hold the soil in place and create air pockets for the water to collect and flow freely through the soil, rather than running off the top.
Other structures that are being used to restore the area are retaining walls made up of sandbags. There are eight locations in the ravine on the steepest slopes where these retaining walls have been placed. This slows erosion. If the bank started to destabilize at the top, the retaining wall would stabilize some of the soil coming down so it does not flow into the water. The City staff are also placing grass and native flower plugs into the spaces between the sandbags to help stabilize the hill and absorb the water.
Other native plants
Christina then identified jewelweed. A couple kinds of jewelweed are found in the ravine, pale jewelweed is yellow in colour. Another type is Touch-Me-Not, which is orange. If you touch it when it is going to seed it will explode and the seeds will fly out. You will be able to see this phenomenon later in the summer along the wood fence near Glen Manor Dr. Jewelweed can be used to relieve the symptoms of minor bites and rashes. If you rubbed it on the rash it would take away the itch and reduce the rash.
Near the creek forget-me-nots were growing. Next, in a low area surrounding the creek near to Glen Manor Dr., there were bull rushes or “cattails”. These appeared to be a native variety as they were growing a little further apart from each other than the non-natives.
Although none were observed on this walk, dragon-flies around the water are a sign of good water quality. They are an indicator species; their larva only develop in water that is clean.
Two other native species in this area on the north east side of the fence are Virginia water leaf and Staghorn sumac. Virginia water leaf is a low growing plant. Staghorn sumac is a medium sized shrub or tree. It is particularly significant as a food source for native birds that overwinter here.
Non-natives and invasives
Diana spent some time explaining what is an invasive plant. Invasives are plants that are taking over an area; they are destructive; they replace other native plants. In this way, they destroy habitat that is necessary for the wildlife of the area to survive and they change the conditions so that native plants no longer thrive. Invasive species are a problem in Toronto and worldwide. Native species are those that are indigenous to Ontario, living here for thousands of years. We also have some species that are not native, but are not considered invasive either – as they do not spread as easily or are simply not as aggressive. Some of the non-natives are brought here intentionally for their beauty. Others are brought unintentionally, due to the worldwide movement of people and shipping, arriving as seeds.
One of our most common invasive plants, although it can be delicious, is garlic mustard. There are examples of it in this same area of the ravine just east of Glen Manor Dr. It has heart shaped leaves which are jagged or toothed and has white flowers. If you roll them up and bend them, they have a garlic odour. You can eat them, but Diana did not recommend doing so. Garlic mustard grows in stands, but the real problem with it is that it displaces native species. It grows here instead of other native plants that would be providing habitat and food sources. You might think it is not so bad. It is green. It fills in spaces. But it is not as supportive as native plants would be.
Another non-native, but not considered invasive plant that was found here, was burdock. You probably notice this plant in the fall. If you brush past it, the burrs stick in your clothing. This is the way this plant can sow its seeds. It hitchhikes on people and animals and then gets deposited in new locations. It has a pretty purple flower when in bloom and looks sort of like a thistle.
Another example of an invasive plant is dog-strangling vine. It was not observed on this walk in the ravine. The City has treated it here and in the park south of the ravine. The name is not representative of what the plant does. It really is no danger to dogs. But it is quite a danger to native plants. It has a habit of growing a long spreading vine, which can twine around and over native plants, blocking out sun and taking away the nutrients they need. It has seedpods with millions of sticky seeds. They disperse like dandelions do, carried by the wind and humans. They are very aggressive, expanding quickly.
One of the bad things about them is that they look similar to a milkweed plant. Monarch butterflies, which are threatened as a species right now, can be confused by them. If monarchs lay their eggs on a dog strangling vine, the larva will not survive as the host plant does not act as a food source for monarchs.
Buckthorn is another non-native invasive species that can be found here.
Some plants that people like to grow in their gardens can also be invasive due to their tendency to spread easily. They have the potential to outcompete native plants in natural areas if allowed to spread. One type of plant is ivy, especially English ivy. You can grow it, but keep it clipped and contain it in your yard. Another popular one with gardeners is periwinkle or myrtle. It grows easily, has purple flowers, glossy leaves and grows in shade. They are lovely plants but they will spread like crazy.
One native plant that is found here that you can grow in your garden, is Virginia Creeper. It is a native vine that you can plant safely.
Next steps – What can you do?
Finally, if you want to protect ravines like this, it is up to each individual to make choices of what to plant in areas that you have control over – your gardens, community plots or in your neighbours’ yards. You can encourage your neighbours to be aware of this information too.
And, you can participate in stewardship activities to help reduce the number of invasive plants. It is a constant battle though, against invasives. You need to be careful when to pull or pick them, to get the whole root and not to disturb them once they have set their seeds. If you do, you may be helping them to distribute their seeds, and they do not need any help. Once you commit to doing it, you need to go back for a few years to be sure to eradicate the species.
Not to end on a down note, there is some hope and progress. The City is currently developing the Toronto Ravine Strategy. Ravines have been an important part of our ecosystem for many years and they have been recognized as a crucial component of our landscape. In the past ravines were incorporated into the City’s bigger land use plans. Back in 2015, the City decided it needed a ravine strategy. In May it started consulting with partner groups like the Toronto Region Conservation Authority (TRCA), the Toronto Field Naturalists (TFN) and many others. The draft Strategy is due to be released for discussion this summer. (It was released in July for consultation by the public.) This is a good opportunity to voice your opinions and get involved in further protecting these areas.Toronto’s Ravine Strategy – draft
Also, Urban Forestry and the TRCA are implementing good forest management strategies to reduce erosion, to remove invasives and to plant natives in many ravines across the city, including the Glen Stewart Ravine. This ravine has a Management Plan that was approved in 2008 and is still being implemented. Urban Forestry Projects
The City also invites the public to participate in stewardship groups in particular locations across the city. Volunteers work alongside the City staff to restore wetlands, ravines and natural areas through these same strategies. You can become part of these efforts at Volunteering in Environment.
Participants were encouraged to join the Friends of Glen Stewart Ravine through our email or Facebook page. And, to continue walking south through the park to see where the creek used to flow and to listen to the sounds of it rushing towards the Lake, beneath the ground.
Thank you to the TRCA, Christina and Diana for an informative evening stroll through the ravine. I hope these notes and photos of plants help others to get further enjoyment out of this special ravine.
Transcribed and edited by Cherie Daly. Reach me at firstname.lastname@example.org