The federal government promised Wednesday to spend $15 million over four years to save a tree-planting program in Ontario cancelled by Premier Doug Ford's government.

Forests Ontario was informed in the wake of the Progressive Conservative government's first budget in April that the program, with an annual budget of about $4.7 million, was being eliminated.

Federal Environment Minister Catherine McKenna said the program is an important part of fighting climate change.

"Planting trees means cleaner air, it means cleaner water, it means more habitat for animals and it also means good jobs," she said Wednesday.

McKenna also slammed Ford for a host of other environmental cuts, including scrapping a cap-and-trade system to reduce greenhouse gas emissions and the green programs that were funded by it. She has criticized Ontario's new climate plan as inadequate.

The money for the tree-planting program comes from Ottawa's $420 million low-carbon economy fund, which was announced last year as a way to bypass the province and give money directly to institutions after Ontario scrapped cap and trade.

McKenna's announcement comes less than five months from a federal election in which Ontario votes will play a key role.

"I think that that's pretty obvious that the federal government wants to campaign against us in this federal election," said Ontario Natural Resources and Forestry Minister John Yakabuski. "It's not the first time they've done it."

Yakabuski said private investors had stepped up in the wake of the cancellation with offers to fund the program, though he refused to say how much money was on the table.

"If private enterprise is ready to fill a gap, is that not preferable to the government putting taxpayers' money into planting trees on private property, when private industry is willing to do it?" he said.

A spokeswoman for Yakabuski said the program had only planted 27 million trees since 2007, well short of its initial goal of 50 million trees by 2020.

Forests Ontario had said the program's cancellation would cause job losses and stall environmental progress.

CEO Rob Keen said the program requires planning several years out for growing the seedlings, and he welcomed news of the federal funding.

"We're just really, really pleased that we're able to partner with you and move forward and continuing to keep this program going, continuing to allow us to do this long-term planning that allows these trees to be planted," he said at McKenna's announcement. "Without this the wheels, I'm afraid, would come off the program and we would just stall out."

The program saved landowners up to 90 per cent of the costs of large-scale tree planting.

It was started as a carbon sequestration program, but planting that many trees also helps clean the air and water, protect shorelines and reduce erosion, Keen said.

About 40 per cent forest cover is needed to ensure forest sustainability, and the average right now in southern Ontario is 26 per cent, with some areas as low as five per cent, Keen has said.