The actor is keen to put an end to the idea that fake Christmas trees are less harmful than real ones through his latest charity campaign.

The Gone Girl star fronts The Christmas Tree Promotion Board's It's Christmas, Keep It Real initiative, which aims to bring "awareness of the benefits of a real tree", while supporting tree farmers, importers and industry partners, according to a press statement from the organisation.

Before joining the campaign, Neil was clueless about the real impact of plastic tree replicas in landfills, confessing he had his facts mixed up.

"I was under the assumption that having a real tree was somehow harmful to the environment, and yet the opposite is true," he tells Mashable. "For trees in America, for every one that is cut down, farmers plant three more. And with the plastic artificial trees that are dumped in landfills, they're in there for a thousand years.

"So I didn't really think of it in that way. And I love it. I love the real tree idea. I love the holidays."

Neil is dad to two young children with his husband David Burtka and he loves the scent of Christmas tree pine when the little ones unwrap their gifts on the big day.

"With kids now, we're real big fans of cookies and fires and smells, and nothing says that more than a real tree, right?" he asked with a smile.