Snap bro I have grew this one haha :P Silica is devloped to help stregthen plant cell walls giving sturdy stalks able to support a PHAT harvest. Being in the nutrient game myself genoneelven.com I can tell you like the other growers have stated she can utilize it right up until the end of growth though we have found the best time to use it is in vegative stage and early flower this way the plants devolope strong sturdy stalks when they need them and we phase it out towards the end so the plant can concentrate more of bud maturity and size though my personal opinion strictly to save you money I would phase it out at around week 6 and replace it with another organic extract that will provide extra energy to you plant during flowering this will plump up the buds much more anything with amino acids in should do the trick though dont just go on my word google is your friend too :) Anyway good luck with finishing her up mine tasted great at the end im sures yours will too :)