You may be surprised at the quality of the weed; it all depends on the temperature of where you live, and the soil quality. There's room for error when harvesting, but obviously you don't want to pull it too young. You need to pay close attention to the resin trichomes; if they're clear, that's usualy the perfect time to harvest; it ensures CBN and CBD cannabinoids are not too high to effect quality. Some people want a more sedating, narcotic high; if this is the case, you may want the trichomes to become slightly discolored.
If you have a good quality high-mag magnifying glass, this will help you observe the development of your crystalline trichomes. If you see none whatsoever, the plant is far too young to pull. Does you're plant have the pungent smell of cannabis? This is a sure sign you're plant is approaching maturity. (Also a dead give-away to nosey neighbours).
Edit: just seen the pic you sent me; your plant appears strong and healthy, but young. I couldn't tell if it's male or female though.
