I don't know actually. But is it that hard to test this? Just make a temp game and try it. Then come back here and post the results.
Then, make an account at the wiki and add the results there:
http://dom3.servegame.com/wiki/
Also: Which spell is this? Is it a nation specific spell? Which age etc. Did you mean the quick roots spell?
This one:
http://dom3.servegame.com/wiki/Quick_Roots
Edit: wow, a bit harsh. Sorry about that. Welcom to the forum!