At least I think that is its name
Adventures if a greenie by vanessa ravencroft. Its been taken down her but is available on inkitt
If that is not it, look at the author Porlock.
Ok, now I'm not on my mobile so I can look it up. The story I was thinking of is https://storiesonline.net/s/44460/green-doom but I'll admit it's not the name of a planet.