While I do count the number of weeks in bloom, my “go to” indicator for when to harvest is the color of the trichomes late in the bloom cycle.

Marijuana trichomes

Marijuana trichomes, All clear, not quite ready to harvest…

Grow guide for marijuana beginners.

Marijuana trichomes at what I consider near peak. A few clear, mostly cloudy, and a few amber ;-)

Marijuana trichomes at what I consider near peak. A few clear, mostly cloudy, and a few amber 😉

Marijuana trichomes

Marijuana trichomes just past their prime (IMHO)

Dry screened marijuana trichomes

Dry screened marijuana trichomes and glandular stalks.