Damn. I knew sleeping was a bad idea. I go to sleep and you guys have a debate over those damn elves lol.
Anyways, I've tried multiple ways of limiting the plants already, you can't remove it from embark/trade. You also can't remove it's biome tags. It won't grow. Thus, the only way, as far as Im aware, is to limit it's frequency and clustersize 0(Which I hope works)