It takes about 4 weeks for Myco to establish itself and become symbiotic your plant. Also, they will lie dormant until a root finds them.Pro mix hp is totally inert Meaning no nutes in it at all. And I dont think mycorrhizae will hurt plants at all. Its in all the fox farm soils i have used and I added great white to every pot I ever grown. And watered in recharge once a week which has that in it mycorrhizae in it as well. I really dont think you can over do the mycorrhizae fungi. I could be wrong.