Watch out when you do get it because equipping it for missions carries a high Golden Crescent cost. Between it and my tranq sniper rifle I was burning through 64 of those plants per deployment, and didn't even realise until I had practically run out. I was forced to drop back to the rank 4 WU which doesn't cost anything to deploy.
Now I'm having to grind those dumb plants, in retrospect I wish I'd spent more time gathering them during missions. I don't mind doing puerile busywork in games but I think sending a legendary soldier* into a warzone to pick flowers is pushing it a bit.
*Yeah I know he's not really Big Boss, thanks kojima.
Powergrind early all the dispatch missions that allow you to gather a lot of plants, you'll have a nice surplus for later.