Best performance is achieved with numerous applications throughout the growth cycle. You can’t “over use” mycorrhizae! But don’t waste product by adding any later than 2-3 weeks before harvest (your mycelial network should already be established). *TIP: Mix the myco in a 1 Gal. jug/container with water to dilute it, pout it into your nutrient solution (ensure you mix-up and pour out the white powder than settles at the bottom of the jug!).*