Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

first, glands are clear. As they continue to mature, they turn a translucent milky color and, finally, they turn amber. Resin glands that are bruised from being squeezed or jostled about deteriorate quickly. All glands do not change color simultaneously on the same bud or plant. The process is gradual, and individual resin glands change at different rates. Of course there are exceptions such as the strain ‘Blueberry,’ which bears darker, even purplish resin glands.

Close-up of a single resin gland was shot with a scanning electron microscope at 370X. THC is concentrated at the base of the “ball.” 370X electron scanning photo courtesy Eirik.

Trichomes are very delicate and can be ruptured easily. Note the torn head on one trichome and the one in the foreground has lost its head completely! 80X electron scanning photo courtesy
    To get a close-up look at resin glands, use a 10X magnifying glass, jeweler’s loupe, or a 20-50X hand-held microscope. My preference is a 30X hand-held microscope with a battery-powered lamp used by stamp collectors. Look at resin glands without harvesting buds, or take a small, thin, resinous portion of a ripe bud and place it under the microscope at a low 30X magnification setting. If the microscope does not have a lamp, a flashlight will be necessary for an un-shadowed view.
    Resin gland development will be in one of three stages–clear, translucent or milky white, and amber.
    Harvest when the majority of glands are clear and a few glands have started to turn milky white. Harvesting plants too early, before a few of the glands turn milky, will make them less psychoactive, because they hold less THC. Harvesting at this point will yield a cerebral, soaring, heady stone. The body will be less affected. Pure sativa and sativa -dominant strains are perfect for this harvest scenario.

This scientist from Canna measures the exact THC content of harvested buds with a gas chromatograph.
     
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    A trichome is a “plant hair.” The trichomes found on drug cannabis are glandular and secretory in character. These stalked glandular trichomes are comprised of a stalk with a resin head. They look like a post with the knob at the top. They form on buds and small leaves. The highest concentration of THC is located at the base of the resin head. The best time to harvest is when these trichomes have developed a spherical head and are transparent to creamy white. Senescing glands start to turn amber and later brown and get smaller; they are decomposing, and THC content diminishes. Check buds every day starting the sixth week of flowering. Check several buds from different plants to ensure the maximum amount of trichomes are ripe for harvest.
    Cystolith trichomes have a pointed tip and are often long and hair-like. These protective trichomes are most common on leaf undersides. Cystolith glands exude insecticidal and miticidal substances to gum up pest mouthparts and repel them, but they have no THC.

The glandular trichomes in this photo are short and stout. Crystalman added color to this photo to provide perspective.
    This close up photo by Crystalman shows a single long tall resin gland that is perfectly ripe.
    Photos on this page courtesy of Joop Dumay, the “Crystalman.” www.crystalman.nl

You can clearly see stalked trichomes, the clear column with a ball on top that contains much THC. Hair-like pointed cystolith hairs contain virtually no THC.
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    Harvest when half (50 percent) of the trichomes have turned a creamy translucent color for absolute peak ripeness. At this point, the high will be both cerebral and physical with a good head and body stone.
    Harvest when the majority of trichomes have turned amber for a body stone. Pure indica, afghani, and indica -dominant strains harvested at this late point will possess a heavy body, or couch-lock, stone. Waiting to harvest pure sativa and sativa -dominant varieties until this stage will not take advantage of the strains. Such strains are best harvested when resin glands are clear to milky colored.
Harvest Step-by-Step
    Step One: Stop fertilization seven to ten days prior to harvest. Latent nutrient accumulation in foliage imparts a fertilizer-like taste. Leach nutrients from the growing medium seven to ten days before harvest. Some growers continue to fertilize until three days before harvest if using a product such as Final Flush®. Such products expedite flushing built-up chemicals from cannabis plants.
    Step Two: If sprays have been