"It wasn't until then that things started to get real for me," he tells the magazine.
"I could sit there all day and do nothing but watch them grow," he says in the January issue of Britain's Psychologies magazine.
These celebrities do it all and we're glad to see that living a go-green lifestyle is one of them.
As part of NBCU Earth Week, check out all of the eco-friendly Hollywood stars in our gallery for some Earth Day inspiration!
The 26-year-old actress is working with Soboroff on a documentary about voting, and the two have become more than close friends, according to U. Dunst previously dated Jake Gyllenhaal and reportedly romanced Orlando Bloom.
» Australian model Miranda Kerr was desperate to turn the page on her career before penning her new self-help book - because she wanted a job with more "substance".