Well this thread is simple... i want everyone to post what they consider the greatest thing they use for growing that makes a huge difference. Whether it be a soil, fertilizer, rooting hormone, technique... anything. The point is to build a compendium of the greatest products of their kind. Please don't mention lights... we all know what ones are good and which ones are bad.

My personal "greatest thing" is foliar feeding... i've cured a bunch of plants with nutrient problems just by foliar feeding them some Miracle-Gro All-Purpose plant food.