Edmonton city workers are battling aggressive weeds with herbicides to protect bio-diversity in parks but some are protesting their methods, arguing that chemicals have no place in natural parkland.

Ida Duncan takes her dogs to Terwillegar Park's off-leash area every morning.

Her pets run freely across the open field, sprinting through grass that grows higher than their ears in some spots.

Duncan pulled into the parking lot last week to find a team of workers in protective gear getting ready to spray chemicals into the grass.

Concerned about whether the herbicide was safe, Duncan says she marched her dogs into the field and refused to budge.

"This is the only thing I know how to do," Duncan said about her impromptu protest.

"I don't want to be difficult, I just know I want to do more research into this."

After a two-hour standoff, Duncan says the workers gave up and left.

Workers geared up to spray herbicides in Terwillegar Park on July 22, according to Ida Duncan, who walks her dogs there every morning. (Ida Duncan)

Edmonton follows provincial legislation to control noxious weeds that could harm humans, agriculture or natural habitats.

The city says workers were prevented from spraying weeds in Terwillegar Park in July, allowing the noxious plants there to go to seed.

"The population increase of noxious weeds in Terwillegar Park is so extensive that chemical control is needed for the city to be in compliance with provincial regulations," a city spokesperson said in an emailed statement.

Since it's too late in the summer to effectively spray the weeds with herbicide, the city plans to mow areas of the park to control growth in August.

Next July, workers will return to the park with a herbicide the city described as having "little-to-no risk for humans, animals or groundwater."

But Duncan said she's rallying fellow dog owners to push for a method that doesn't involve chemicals.

"I'm just so upset about this whole thing," she said.

"It doesn't make any sense because they're just going to have to keep spraying all the time. So that means the dogs are going to be running through it, we're going to be walking through it, we're all going to be taking it to our homes. It's just not right."