Trichomes is the only real way. You need a pocket microscope for $8 from Radio Shack.

Harvest clear - Clear, able to think stone
Harvest cloudy - Normal stone
Harvest amber - Narcotic, couch lock stone.

I try for 10 percent amber.
Opie Yutts Reviewed by Opie Yutts on . harvesting? What is a good way to know when to cut and dry the plants? Rating: 5