The thing I hate about Treant Protector

I HATE how NO ONE in pubs or even my friends know how to use Nature's Guise properly when I cast it on them.
I love all other aspects of Treant Protector, but for whatever reason, my friends refuse to remember that they need to stay at the tree line to be invisible.
How did you guys overcome this hurdle?

Only cast it on them when they are between trees and has to walk near them to get to the enemy. :D

Get better friends / get to a higher skill level.

Alternatively, I doubt that they really don't understand the mechanics. Consider frequent communication to signal that you will be using Nature's Guise on who and for what specific reason, followed by a reminder that they shouldn't get away from the tree radius. If they really don't know how it works, then explain. If they do not understand, then I would seriously consider looking for better friends and play with them (unless these friends you speak of are your friends irl), at least for getting yourself to a higher level.

Emphasis on the communication thing though,

Shout at them in Russian, it always helps when people do that :p

Seriously though, just play games and if anyone seems to understand it instantly friend them :-)
Using a microphone would be very beneficial for using the skill, so they know you are about to do it.

It's unfortunately one of those things - some peeps don't understand how many heroes' powers work. They'll usually try to inflict their ignorance on you. I had an American Riki screaming abuse down the mic at me yesterday because I wasn't using my Disruptor's Thunder Strike on the enemy Bounty Hunter while waiting on money for Sentry Wards.

Trying to explain to somebody with serious anger managment issues why it's not worth throwing out 130 mana to inflict 30-45 actual damage is hard going.

Yeah you can't assume people will use nature's guise properly. Especially in a pub. TP is not that popular as a hero and having one that is good enough to use an ability like nature's guise is probably even less common.

I have had teammates not know how fatal bonds work. Even after I tell them. In all fairness they may have been Chinese.