Category Archives: Invasive species

Bull Thistles

Bull thistles are the most common thistle in Raymore Park. They are found throughout the park’s wild areas and despite the prickles, their leaves are a source of food to deer and rabbits while insects and hummingbirds feed on their nectar. Apparently the roots when boiled taste like a Jerusalem artichoke and the leaves can be cooked and served spinach-style. Bull thistles are another eurasian invader but seem to have found a niche without being too invasive.

A bee sips nectar from a bull thistle in Raymore Park’s wild area. Click to enlarge.


More signs of fall

Ever since Codemonkey pointed out a great spot for turtle watching, I’ve noticed a turtle regularly sunbathing in the same spot in the recent warm weather. It seems to be a painted turtle and is very shy, darting into the water if anyone approaches within 20 metres.

A painted turtle enjoys the last of the warmth.

A painted turtle enjoys the last of the warmth.

Dogwood is fruiting in many parts of the park and soon its leaves will fall away to reveal its distinctive red branches.

Red Osier Dogwood.

Red Osier Dogwood getting checked over by an Asian lady beetle.

The unusually coloured berries are popular with migrating birds and were once used as a native remedy against colds.

The ladybug, ladybird or Asian lady beetle on the dogwood is a powerful invader that is elbowing native ladybugs aside in many parts of the world. Introduced by greenhouse growers and perhaps the U.S.D.A. the ALB escaped into the wild and there will be no going back. Native ladybugs eating toxic ALB larvae do not survive. Once established in Canada, the ALB tainted many Niagara wines as growers couldn’t separate the bugs from the grapes. Armed with powerful chemicals, it takes only a few of these bugs to taint a whole year’s wine production. Having experienced some Chateau Ladybug (at a winery that was shamelessly trying to offload it) about ten years ago, I can vouch for its unpleasant and unforgettable taste.

Signs of Fall: Atlantic Salmon are climbing the ladder.

Two hundred years ago, Atlantic salmon along with many other varieties of fish were plentiful in the Humber. Gradually, settlers built dams and toxic waste from sewers, factories and pulp mills was dumped into the river. The combination killed just about everything in the water and Atlantic salmon were extirpated from the Humber as a result. In 1959, the opening of the St Lawrence Seaway saw the accidental introduction of the parasitic sea lamprey which killed the rest. An ambitious program lasting several years aims to restore a self-sustaining wild Atlantic salmon population to the Humber. Each spring until 2015, salmon fry are being released all along the Humber. Most weirs along the river have been adjusted to be too high for lamprey but low enough for migrating fish.

In Raymore Park, the 3 metre weir remains an insurmountable barrier to all aquatic life and to work around that, a denil fishway, (better known as a fish ladder) was built around 13 years ago.

The fish ladder entrance is on the left just below the weir.

The fish ladder entrance is on the left just below the weir.

The fishway provides a gentler current and slope so that large fish can make their way up the ‘ladder’ with rest stops along the way. Unfortunately, beavers stuff the fishway with wooden debris in the hopes of creating a dam. Needless to say, the blockages need to be cleared several times a year so that fish can migrate to their spawning grounds.

On Friday, two workers were clearing the way for the salmon and told me that when water levels rise (as they did on Saturday), these large Lake Ontario fish will be able to access and use the ladder. From there they will swim upstream to their birthplace, spawn and return to the lake – assuming they can run the gauntlet of people out to get them.

TRCA workers clear the top of the fishway.

Toronto and Region Conservation Authority workers clear the top of the fishway.

Since the ladder was built I have watched in vain for a fish to appear at the exit. Today, (Tuesday September 24th) I had a premonition and with the camera ready, just like that, a fish emerged. The water was a little murky and I was a little late but here’s the evidence; the ladder works.

The salmon continues its journey up the river.

The salmon (middle top of photo) continues its journey up the river.

In spite of their impressive size, salmon will soon be seen along the Humber as far upstream as Bolton and Palgrave.

For its part, the TRCA is studying the further removal of obstacles to fish migration along the Humber and the weir in Raymore Park is the highest. Lowering and notching of the weir will allow the fish to leap upstream the old-fashioned and low-tech way. This will end the high maintenance costs of the fishway and finally allow the beavers to block it to their hearts’ content.


A couple of shots illustrate one of the habitats in Raymore Park.

A bull thistle stands guard over a field of queen anne's lace.

A bull thistle stands guard over a field of Queen Anne’s lace.

The field in question will be a small wood in a few years thanks to native saplings in place for several years. For now, weeds and wildflowers are enjoying the space. Bull thistles are not native but seem to be the most common thistle in Raymore Park. Members of the aster family they propagate by seeds alone. The roots and leaves are edible with some preparation.

Queen Anne's lace

This Queen Anne’s lace has a tiny red flower.

Another foreign invader (from Europe), Queen Anne’s lace is a member of the carrot family and the root is edible. Being a biennial plant, it flowers and dies in its second year. Insects love QAL and so it can’t be all bad.

Dog strangling vine

North America is a continent with many points of entry for invading plants and animals. Its climate zones go from Arctic to tropical so there is a comfortable zone somewhere for any invader. If the newcomer has left its enemies behind, a veritable breeding frenzy ensues. Once the continent has been breached, with the current state of biology, we’re stuck with the invader forever.

A relative newcomer is once again sweeping North America since its introduction (probably accidentally) from Europe where it is native. Dog strangling vine or swallow wort (Cynanchum rossicum) is related to milkweed and grows almost to 2m in dense clumps, hence its common name. Quite at home in southern Ontario, it has been around for decades and is regarded as a bigger menace than garlic mustard by many. In Toronto’s High Park, desperate measures (using Roundup) have been used after physical attempts to remove the plant failed.

This dense patch is by the river in the wild area.

This dense patch by the river in the wild area has already out-muscled the competition.

The seeds look a little like milkweed seeds and in fact the plant can confuse Monarch butterflies into laying eggs on it. Given a choice, Monarchs will lay eggs on DSV 25% of the time. Monarch eggs laid on DSV will not survive.


Flowers are tiny but produce lots of seeds.

This plant seems to have few redeeming features although cattle will eat it.

The answer to this problem (once again) seems to lie in biological control through careful importation of benign enemies. This takes time to ensure that adding another import to the long list doesn’t backfire.

One can only wonder which other invaders are waiting in the wings.