Here is a close-up of a cannabis plant's capitate-stalked resin glands shot at 180X magnification with an electron-scanning microscope. Note the globe on top of the stalk is ruptured and cannabinoids are exposed to air and light. (Courtesy of Jorge Cervantes via "The Cannabis Encyclopedia")

When is it the right time to harvest cannabis? Look for these signs

Cannabis Cultivation Q&A: It's one of the most eagerly anticipated moments for a grower — here's the skinny on knowing when to harvest marijuana

Renowned grower Jorge Cervantes will answer readers’ questions and give advice on all things related to the cannabis plant. Got a question for Jorge? Email him at jorge@marijuanagrowing.com.

Editor’s Note: Laws for cultivating cannabis vary from state to state and city to city — before germinating any seeds or planting any clones, take care to learn what your local laws are.

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Question: What’s the best way to tell when my buds are ready for harvest?

Answer: A cannabis plant matures over time; it is a process. Cannabis is an annual plant, completing its life cycle in one year or less. Outdoors, cannabis flowers in the fall. Long nights and short days are the main signal Mother Nature gives cannabis to flower. Indoors, where grow lights take the place of the sun, growers use an electrical timer to make their own seasons. Summertime is created with 6 hours of darkness and 18 hours of light. The fall flowering photoperiod is replicated with 12 hours darkness and 12 hours of light. Female cannabis plants are ready to harvest in 6-12 weeks after the light has been “flipped” to a 12-hour day/night regimen. As the plants mature, there are certain clues to guide you in knowing when to harvest cannabis.

First clue: Have the stigmas changed?

Look at the white fuzzy hair-like stigmas protruding out of the seed bract on buds. White stigmas are healthy and turn a reddish-brown when they die back, or senesce. When half to three-quarters of the stigmas have turned reddish-brown flower buds should be ready to harvest. But, you need to take a second look, a closer look.

Second clue: Examine the resin glands closely

Use a 30-50X handheld microscope to inspect the resin glands, a.k.a. trichomes, found on flower buds and adjacent foliage. I like to use a microscope that illuminates foliage to get an unshaded view of the translucent resin glands. The microscope will allow you to distinguish several resin glands. The important ones are the capitate-stalked resin glands. They consist of a stalk with a small, spherical globe on top. Be careful when viewing resin glands, they are quite fragile.

The majority of tetrahydrocannabinol (THC) is located at the base of the globe where it joins the stalk. Fragile capitate-stalked resin glands start to senesce as the plant nears the end of life. The globe starts to degrade first and cannabinoids leak out. Exposure to air, heat and light can speed degradation. Oh yes, fondling flowers can also wreck a lot of capitate-stalked resin glands!

Cannabis is ready to harvest when a small percentage to more than half of the capitate-stalked resin glands have started to degrade. They turn amber and darker colors when they degrade. Some growers prefer to harvest earlier than later; others, later than earlier. It is all a matter of preference, which leads to the third point, consumption.

Third clue: Sample the bud

Dry a few flowers in the oven, 150 degrees F for 10-15 minutes. Smoke or vape it and see what you think!

Flower buds do not all mature at the same time. Often, flowers that receive more light and are on top of plants come ripe a few days to more than a week before lower buds. The difference in cannabinoid content, including potency, can be notable. Flowers from short plants grown indoors have less deviation in cannabinoid content than large plants grown outdoors.

There are countless varieties of cannabis. Indica-dominant varieties tend to be ready to harvest in 6-8 weeks after an indoor light regimen is turned to 12 hours dark and 12 hours light. Sativa-dominant varieties tend to be ready to harvest from 9-12 weeks after light regimen is changed to 12/12.

Outdoor crops that cannot be protected should be harvested if there is chance of a freeze or violent rainstorm.

Indoors or out, harvest in the morning whenever possible. Flowers near the tops of indoor and greenhouse plants may be a few days more mature than flowers that receive less light; in this case staggering the harvest is a good idea. Lower flower buds on outdoor plants that receive less light mature more slowly, up to two weeks after flowers near plant tops. Once flower buds are completely mature and ripe, the harvest window lasts from 3-5 days.

This is a quick overview of the best time to harvest cannabis. For complete instructions, including many descriptive color photos, check out “The Cannabis Encyclopedia,” available on Amazon.com.

Your opinion matters
When do you harvest? How do you minimize the work? Do you save leaves for edibles? Please share your tips and tricks with everybody in the comment section below. Thanks!