A Renfrew woman has been told she'll have to avoid direct sunlight for three years after a nasty encounter with toxic wild parsnip in her garden.

Sherry Steeves was gardening two weeks ago when she had a run-in with the wild parsnip, an invasive species that's a close relative of giant hogweed.

Later that day, she spotted black markings on her leg — and that was just the beginning.

"About eight hours later I noticed I had three holes that looked like sirloin steak," said Steeves. "My whole thigh was all blistered and swollen. Very hot, like burning."

The toxins in the plant's sap can create what is known as "phytophotodermatitis" — basically an extreme sensitivity to sunlight.

The effects of the toxins are not felt immediately but once activated by UV rays, they can damage skin cells and cause lesions that look similar to burns.

jeff muzzi forester wild poison parsnip july 9 2015

Forester Jeff Muzzi says the clear sap of the wild parsnip's stem is what makes people's skin ultrasensitive to UV radiation. (Ashley Burke/CBC)

"If you get it in your eyes it can actually cause blindness," said Jeff Muzzi, a local forester who's dealt with the plant before.

Ottawa roads 'highly infested'

In 2014, the City of Ottawa mapped wild parsnip growth across the city, and found more than 200 kilometres of mostly rural roadsides that were "highly infested" with the plant, according to a May 2015 report to the agriculture and rural affairs committee.

The city has earmarked $100,000 to deal with the infestation, said Luc Gagne, the manager of road services with Ottawa's public works department. 

"We sprayed approximately 250 kilometres of roadsides and sprayed by backpack some passive park areas," said Gagne.

'Vampire syndrome'

As for Steeves, she said her doctor has now told her to cover up and stay under an umbrella when it's sunny out.

That's drastically changed her lifestyle, she added.

"Vampire syndrome, I've named it. Because you can go out at night and do what you want, but during the day you have to hide because the UV rays will burn you," said Steeves.

"All of the sudden you can't go in a boat. You can't go canoeing, really. You have to stay totally covered up all the time because you don't want to set it off again."