dependds on strain. usually about 6-8wks in short cycle, but can take longer depending on numerous things. Strain, room temp, fert,h20 ph.....get what is called a jewlers loup(microscope kinda deal) and look at the crystals. when the crystals turn milky white is a good indicator their ready! the heads on the crystals also start to erupt like a mushroom . try a grow shop or pawn shop ofr a loup!good luk. it just takes time and experience as to how you like them done. be patient, ive seen ladies dubl in size the last week!