Ontario's Minister of Northern Development and Mines marked his first day back on the job, after a five-month leave to recover from depression, with a celebratory announcement Monday.

"It's a nice thing," said Michael Gravelle, who is also the MPP for Thunder Bay-Superior North, of the chance to ease back into work with a project aimed at making Ontario cleaner and greener for future generations.

The provincial government is distributing seed pods for 15,000 Eastern White Pine trees at schools and community events across Ontario, he described.

"The Eastern White Pine is the official tree of the province of Ontario and we want to be able to re-green the province," Gravelle said. "These can grow into incredible, beautiful trees in our conifer forest and I'm just glad to be able to use this as an opening to me returning to my ministry."

Adding beauty to landscape, neighbourhoods

The Eastern White Pine has long been considered one of the most valuable timber species in North America, he said, adding the trees grow to nearly 40 metres in height and can live as long as 500 years.

"In the 17 and 1800's these tall, sturdy, straight trees were constructed into ships' masts and the best were stamped and claimed by the Crown for their Royal Navy vessels."

Gravelle also praised the trees for adding "beauty to the natural landscapes along our highways and waterway and in our neighbourhoods and parks."

The veteran politician participated in planting a white pine sapling on the grounds of the provincial government buildings in Thunder Bay. 

Eastern White Pine

Eastern White Pines, like this tree waiting to be planted in Thunder Bay, Ontario can grown 40 metres in height and live 500 years. (Cathy Alex/CBC )

The seed pod program is also being used as a way to mark the sesquicentennial anniversary of both Ontario and Canada.

As part of Ontario150, the provincial government is encouraging the public to plant more trees, said a news release from the province on Monday. Every year, Ontario plants three million trees.

This year Ontario is challenging the public to match its target as part of the Green Leaf Challenge.

Participants can register trees they plant, including these eastern white pine seed pods, on an interactive map at GreenLeafChallenge.ca.