One of the largest porn websites in the world has promised to plant a tree for every 100 videos viewed online.

Pornhub unveiled its novel way to help support the environment in celebration of Arbor Day, a US holiday which encourages people to plant and care for trees.

The website, which is reported to attract more than one billion monthly visitors, said it will plant one tree for every 100 videos viewed from its 'Big D**k' category.

The website said on its SFW campaign page Pornhub Gives America Wood: "While you're watching some nice pieces of ash, you'll also be helping to spruce America up! (Bushes are optional)."

So far, Pornhub has promised to plant more than 10,000 trees because of the promotion. It is not known where the website plans to plant the trees or which organisation will help them to do so. Pornhub are reportedly deciding between three groups: Arbor Day Foundation, Trees for the Future or American Forests.

"At Pornhub, we give a countless amount of wood every day," spokesperson Mike Williams told Mashable. "Playing off that, we saw an opportunity to promote our brand and give back to the community."

"Whatever the species, our trees will grow up to be long and hard and, with any luck, they will go on to spread seed of their own."

In the past, Pornhub said it would donate 1 cent for every 30 videos viewed on the site towards breast cancer awareness charity Susan G Komen Foundation.

However, the hardcore porn website was left red-faced after the charity rejected their offer for donations and asked them to stop using their name.