The City of Edmonton will go back to spraying sports fields with herbicides at the end of June in an effort to control dandelions.
The dandelions will be sprayed with iron chelate, a "low-risk herbicide" that is absorbed into the weed and turns it a dark red-black colour, but leaves it safe to touch, said Doug Jones, deputy manager of operations.
The city will aerate and add top dressing to its 1,465 sports fields as well.
"I believe that our chosen approach reflects the right balance of safety, environmental, social and financial considerations," Jones said on Friday.
"It is time to take action."- Travis Kennedy, parks operations
Parks will not be sprayed. The city will continue to try to control dandelions and weeds on roadways and parks by mowing.
One spray truck will operate in each of the four quadrants of the city, said Travis Kennedy, acting director of northeast district park operations.
Spraying will begin early in the morning, at 6 a.m. or 7 a.m., once the overnight dew has dried on the fields, he said.
City council voted in June 2015 to stop spraying herbicide on city land, with a few exceptions.
This year, dandelion blooms quickly took over the sport fields, making them difficult to run on and creating what Jones previously described as "trip hazards," creating a safety risk.
"There are many dandelions on our sports fields," Kennedy said. "I don't know that we're at the point where the dandelions are choking out the grass."
But he added: "It is time to take action."
Treatment will start in late June and continue through July, with each field sprayed twice.
Iron chelate dries quickly, between 30 minutes and three hours after application, depending on the weather, Jones said.
Signs will be posted advising people when the fields are being sprayed.
The herbicide has no strong odour, does not leave a chemical residue, and poses negligible health or environmental risks, said Jones.
The applications will cost a total of $750,000, five times more than the aggressive herbicides the city has used in the past, he said.
"It was a balance of finding a product that was going to be effective to do the job we needed to in a relatively quick time frame," he said. "And be safe and environmentally effective as well."
Applying iron chelate to parks, roadsides and sports fields would cost as much as $10 million, the city estimates.
The city maintains 4,100 hectares of grass, equal to 7,000 CFL football fields.
Sports fields make up about 11 per cent of that.
The city will only get around to spraying about 60 per cent of the sports fields this year, said Jones.
How the city might deal with dandelions in future years will be discussed when a report comes before city council on Aug. 29, he said.
Homeowners are allowed to use herbicides purchased at hardware stores or garden centres, but only on their own yard, said Jim Hole, co-owner of Hole's Greenhouse.
"You cannot go to a boulevard, can't apply it to a neighbour's yard, and you can't go to a playground," Hole said.
The herbicides are safe to use, he said.
"It's not like painting a wall," said Hole. "The herbicide is absorbed very quickly through the foliage. So you don't have any great amount of residual on the foliage itself."