Ive tried many.many bloom boosters from the big bud tribe collection from Advanced, too PGR and PGH containing Liquid W8, and massive . i believe this does contain natural PGR but it certainly does the job. Of course if using composted soil, your application rates are odd. I find any flower booster in an organic composted soil setup, use a week before you flip too get mich more bud sites, in autos as soon as you see the first lil hairs.