You'd have to not use any kelp, rooting hormones, yeast, almost any booster product to be totally pgr free. Like anything there are good and bad, effective and not effective ones. I can say that growing with just nutrients is rewarding and a great learning experience, but in no way are you affecting the experience in a profound way by using natural bio stimulants and pgrs. Tria is no big deal, although i always recommend testing everything before using it a second time. Just trusting you'll notice is how you become one of those been growing for 10 years but no nothing type of gardeners. Dont be one of those gardeners.