You’ve planted your seeds, lovingly watered your crop, and watched your plants blossom into gorgeous, pungent flowers. If you’re new to growing cannabis, you’re probably wondering when you should harvest your marijuana plants. Harvest too soon, and your buds won’t reach their peak THC level. Harvest too late, and your plants will lose some of their potency. We’ve created this guide to help you determine when the time is right to harvest your cannabis.
Best Time to Harvest Your Marijuana Crop
When it comes to harvesting the highest-quality marijuana, timing is key. Most plants are ready to harvest 8-10 weeks after flowering. If you purchase your seeds from a reputable breeder, they may offer valuable insight into the peak harvest time for your particular strain. It’s best to use your breeder’s recommendation as an estimate, but it should not be considered a hard and fast rule. Many environmental factors will impact the time it takes your plant to reach peak maturity. It may take a few attempts to find the sweet spot for each particular strain, but after a little trial and error, you will be able to tell when your buds are ready to harvest.
How to Tell When Your Marijuana Plants are Ready to Harvest
There are several sensory cues that indicate when your cannabis crop is ready reap. Some can be observed with the naked eye, but the best results require some additional equipment.
- Fan leaves turn yellow. Before flowering, the wide leaves of a healthy marijuana plant should be bright green. Yellow leaves during the seedling, vegetative, or early flowering phase could indicate a number of potential issues. As the flowers become more developed, however, your plants will pull their resources toward the buds, often causing the lowest leaves to turn yellow and even die. This is a good initial indication that your flowers are getting ready to harvest. Close to harvest time, remove these yellow leaves from the lowest 25% of the plant
- Fragrance increases significantly. Marijuana’s fragrance is determined by its terpene profile. Terpenes are chemicals that naturally occur in plants and produce a scent. As cannabinoids mature, so do terpenes. When your plants are ready to harvest, they should have a strong and distinctive odor.
- Pistils change colors. Pistils can be observed without a magnifying glass. These hair-like growths are the female reproductive organs of the cannabis plant. If a male pollinates the female plant, the pistil will produce a seed.
The pistils of most marijuana strains will begin to undergo a noticeable change as the plant begins to mature. Flowering plants will begin with white pistils that stick out from the calyx of the flower. At harvest time, the pistils will darken and begin to curl.
It is common to see the color of the pistils change from white to amber, orange, red, pink or brown. Not all of the pistils darken at once, meaning you will typically see a mixture of white and darker hairs on the same plant around harvest time. Some strains, such as The White, Mr. Nice Guy, and White Window, retain their white pistils well into harvest time. It’s best to consult with your breeder or grower to find out what colors to expect when your plants are mature.
If you’re using this method, make sure to exercise patience. According to Robert Bergman, author of Marijuana Grow Bible, you’ll want to wait until over 50% of the pistils begin to darken and curl for peak levels of THC. He recommends waiting to harvest until 70-90% of the pistils have darkened. Waiting too long to harvest will result in your THC converting to CBN, however new growers are far more likely to harvest too early.
- Trichomes become milky white: Resin glands, also known as trichomes, are hair-like outgrowths that cover the leaves and buds of cannabis plants. Not to be confused with pistils, they appear tiny, glittery, and dust-like to the naked eye, but are more intricate upon closer inspection. For the most accurate method of determining whether your buds are ready to harvest, you’ll need to use a magnifying tool to observe the subtle changes in the trichomes.
Serious marijuana growers use a digital microscope to get an up-close look at the trichomes of their plants. Digital microscopes can carry a hefty price tag and will need to be connected to a laptop or other screen. A less expensive alternative is the jeweler’s loupe, which is essentially a high-caliber magnifying glass. These are available online for around $20. Smartphones with advanced camera capabilities serve as an excellent substitute. Some growers even prefer them because of the ability to zoom and to save daily progress images.
Immature trichomes are clear and crystal-like. According to Bergman, you should wait to harvest until 50-70% of the trichomes appear milky or cloudy white. As they age, some of the trichomes will turn a dark amber color. This is a sign that some of the THC have begun converting to CBN. For a more relaxing, “couchlock” effect, Bergman recommends harvesting when 70-90% of the trichomes have darkened to amber.
How Maturity Impacts Cannabis Effects
In his exhaustive report, Marijuana Botany: An Advanced Study, Robert Connel Clark sums up the importance of timing your harvest properly:
“Some like to harvest early when most of the pistils are still viable and at the height of reproductive potential. At this time the resins are very aromatic and light; the psychoactive effect is characterized as a light cerebral high. (Possibly low CBC and CBD, high THC, low CBN). Others harvest as late as possible, desiring a stronger, more resinous marijuana characterized by a more intense body effect and an inhibited cerebral effect(high CBC and CBD, high THC, high CBN)”
Simply put, the maturity of the plant at the time of harvest can impact the type of high users experience. Clark goes on to describe the effects of marijuana harvested at various stages:
Early Floral Stage: “Total cannabinoid production has increased markedly over the premature stage but THC levels (still less than 3%) are not high enough to produce more than a subtle effect.”
Peak Floral Stage: “Many cultivators prefer to pick some of their strains at this stage in order to produce marijuana with a clear, cerebral, psychoactive effect. It is believed that, in peak floral clusters, the low levels of CBD and CBN allow the high level of THC to act without their sedative effects”
Late Floral Stage: “Cannabinoid production favors high THC acid and rising CBN acid content at this stage….This tends to produce marijuana characterized by more somatic and sedative effects.”
The outermost buds of the marijuana plant mature faster than the inner buds. You can increase your yield by performing multiple harvests, waiting to perform a second harvest until the younger buds become more mature.
Knowing when you should harvest marijuana plants is a practice that is comprised of equal parts art and science. You don’t have to be an elite grower to raise a great crop. With the right tools, a trained eye, and a lot of patience, you will soon be able to produce your own high-quality cannabis.