The city of Thunder Bay is trying out a new way to keep its urban forest healthy.

A donation from the TD Green Streets program has paid for 400 watering bags that will be placed on the trunks of trees that were recently planted around the city.

Urban Forest program specialist Rena Viehbeck says it's a good way to deliver 75 litres of water to tree roots.

Thunder Bay has been given 400 tree watering bags to use with newly planted trees. Rena Viehbeck

“That amount of water gets slowly released right onto the roots below, over the next six to nine hours,” she said. “That water will actually reach the roots, without running off, which often happens when people water too fast.”

Homeowners with a bag in front of their house can refill it themselves — usually once a week — otherwise a city worker will do the job this year.

Thunder Bay was one of 21 municipalities selected to receive a grant from TD. Last year the city received a TD Green Streets Grant to help launch the new Citizen Pruner Program.

"The goal of TD Green Streets is to encourage the adoption of leading-edge practices in municipal forests," said Mary Desjardins, executive director, TD Friends of the Environment Foundation.

"We want to commend the City of Thunder Bay for developing a program that will provide such a great enhancement to the environment."

Tree watering bags are an efficient way to water newly planted trees for up to two years after they have been planted, a city press release stated. After two years, tree watering should be located outwards of the tree's drip line — to where the roots will have grown.

"Proper soil moisture for root growth is especially important for newly planted trees," said Viehbeck.

"Lack of water is the single greatest factor that leads to the death of newly planted trees. Slow water application, by using a tree watering bag or leaving your hose on at a slow trickle for one-to-two hours prevents surface runoff and allows the water to reach the absorbing roots of the tree."