6 invasive plants in the Yukon and what you can do about them

Invasive plant species are becoming a growing concern in the Yukon.

"There's upwards of 20 [invasive] species and that list sort of fluctuates," said Shonagh McCrindle, executive director of the Yukon Invasive Species Council.

Invasive plants spread, change the makeup of the soil and generally prevent native plant species from thriving in their natural environment.

Most of the invasive plants across the territory are in full bloom right now. The best way to manage them and minimize their long-term impact is to pull them out but what to do after that depends on the plant.

Here's what to do with the six of the most common species across the Yukon.

Sweet clover

Sweet clover is the most common invasive species across the territory.

"That one's the worst," said McCrindle. "It's so bad because it creates so many seeds. It really can spread very rapidly, as we can see in the fact that it's everywhere."

"It's got little white flowers and it's quite pretty and it smells sweet. It's alongside every single highway and every roadway in the Yukon." 

There are white sweet clovers and yellow ones. Both should be treated the same way.

The invasive plant is flowering right now but will turn to seed within a week or two, said McCrindle.

"Whatever seeds get scattered this summer will be in the ground for 10 to 15 years and so it will require, you know, at least a 15-year plan to mitigate," she said.

The thing to do with the plant now is to simply pull it out of the ground, preferably before it turns to seed.

Once it turns to seed, McCrindle said the plant should still be pulled.

"The seeds will still probably thrive in the next year, but you're still getting rid of the mature plant," she said.

The plant has a relatively big taproot, McCrindle said, so once it gets to about the size of a bush, pulling them up "can be a bit of a two hand full body thrust sort of affair." 

Once the plants are pulled, it's best to collect them and then compost them, she said.

Narrowleaf Hawksbeard

Another very common invasive plant across the Yukon is the Narrowleaf Hawksbeard.

It has dandelion-like yellow flowers and grows to a height of between 20 and 60 centimetres.

"People should pull them out but they have to be put in bags and thrown into the garbage because the flowers continue to seed even after they've been pulled," said McCrindle.

She said that if they're then placed in a clear, plastic bag, and put out in the sun, it will roast them

"It'll kind of cook them. That's the best," said McCrindle.

She added they're very easy to pull because they have dainty, little roots.

Sow thistles

Perennial sow thistles also look like dandelions, but they can grow to a height of two metres.

They need to be pulled as well, and then bagged and thrown into the garbage, according to McCrindle.

They can be hard to pull once they've grown enough because they have big roots, said McCrindle.

"When you pull them out, you have to try and get as much of the root as possible," she said.

They're found primarily in Whitehorse but have also been spotted further north, in Carmacks.

Oxeye daisies

In some places, oxeye daisies are sold as a garden plant and it's not uncommon for people to plant them in their garden. But it's not a good idea.

"They're very pretty, but they're invasive," said McCrindle.

"They'll hop out of your garden, into your lawn and then across into the forest."

They can form dense colonies and replace up to 50 per cent of grass species in a pasture.

She said they should be pulled and put into the garbage as their roots can sprout new plants.

Bird vetch

Bird vetch has distinct blue or purplish flowers arranged in a one-sided spike.

McCrindle said there's an infestation of them in Whitehorse's Range Point neighbourhood where illegal dumping of yard waste has taken place.

"All of a sudden, there was this massive overgrowth of bird vetch in a completely natural environment," she said.

A group of volunteers with the Invasive Species Council has been managing the infestation there for the past four years, going in every year to pull them out.

McCrindle said pulling them works if the infestation is small and then monitored for a few years. Otherwise, herbicide is recommended to control them if the infestation is large, she said.

She added that when they're pulled, they need to be bagged and thrown into the garbage.

Butter and eggs

Butter and eggs look like a yellow perennial snapdragon and they can be found all over the train tracks in Whitehorse.

"The train tracks aren't a really big deal because they're not a natural environment but it's when they creep into areas where they shouldn't be that's the problem," said McCrindle.

Butter and eggs can be very dense and suppress native grasses. Their roots can sprout a new plant.

They also contain a poisonous compound that isn't good for livestock or other animals who eat them, according to McCrindle.

Like many other invasive plants, butter and eggs need to be pulled and bagged.