trichomes start off clear but as they mature they turn amber or light brown. This are actually the “red hairs” that develop when your bud are fully developed. You’ll know that THC is starting to build up when the membrane around the glands begin to swell and appear like mushrooms. Growers can start their harvest when 50% to 80% of the pistils have turned from white to dark red. Also, plants can be harvested when approximately 50% of the trichomes begin to become amber.