When to harvest marijuana: a comprehensive guide

when to harvest marijuana: person holds harvested plants in field

Growing cannabis plants is a love-filled experience that’s often filled with many questions. Choosing between soil and coco, calculating the growth cycle, and understanding nutrients are just a portion of the work–and it all takes research and guidance to pull it off without a hitch. A topical cannabis cultivation query this time of year is when to harvest marijuana. Many cannabis cultivators have a mentor to ask questions, but those who don’t often turn to literature for the answers.

The thing about growing cannabis is that every cultivator has a slightly unique methodology. This is generally developed after seasons of farming luscious flowers, learning from mistakes and triumphs. When it comes to harvest, every grower has one thing in mind: pulling plants when they’ve reached their optimal levels of cannabinoids and terpenes.

“Harvesting takes place at the end of flowering when the buds are at their peak ripeness, before the plant’s psychotropic or medicinal resin begins to degrade,” reads Marijuana Harvest, a book by Ed Rosenthal and David Downs.

Key Takeaways:

  • Cannabis trichomes tell a grower when it’s time to harvest.
  • When all the heads are translucent and some trichomes have turned milky, it’s time.
  • Amber trichomes signify that the plant compounds like THC and CBD are degrading.
  • Use a magnifying glass to keep tabs on what phase trichomes are in.
  • Not all buds or resin glands develop simultaneously – watch the whole plant.

when to harvest marijuana: close up of someone trimming buds off of a plant

While every cannabis cultivator has particular methods, there are many things that all growers use to identify that a cannabis plant is ready for harvest. Ed Rosenthal and Jorge Cervantes have served as a mentor to countless modern home gardeners and industry professionals. Their works have built a foundation since growing a plant was a highly illegal endeavor.

Ed Rosenthal has penned at least seven books on growing weed. His books cover the process from seed to the flowering stage and beyond. Jorge Cervantes’ cultivation books have been equally revered for generations as he wrote about the life cycle of the plant.

In Marijuana Harvest, Ed Rosenthal and co-author David Downs highlight the need for care even after the plant matures:

“Even large commercial operations are sometimes far behind in harvest and post-harvest operations. These final tasks need the most thought; they are the ones most likely to be improperly executed—but they needn’t be. With proper preparation the process can flow seamlessly,” they write.

Cervantes highlights the need for work before harvest..

“The payoff for all the research, work, risk, expense, and the long, patient wait is a bountiful harvest…A well-organized pre-harvest and harvest are essential to preserve cannabis quality and decrease the workload,” Cervantes writes in Marijuana Horticulture.

Cannabis harvesting basics

Harvesting cannabis buds is a five-step process crucial for capturing a rich terpene profile, THC, and CBD. It also ensures the plant retains enough moisture to stay dank without molding.

To get cannabis harvested, growers must:

  • Cut down branches with buds
  • Cut buds off of branches
  • Trim
  • Dry
  • Cure

Each step requires some planning, specific tools, and effort. At the worst, improper harvesting methods turn a crop into garbage, at the easier end, trichomes will be over or under-developed or destroyed.

Every part of the process is crucial, but the most crucial step depends on knowing when to harvest marijuana.

When to harvest marijuana

Observing the color of the trichomes is the best way to gauge if a bud is ready to harvest. This is called the trichome method. The mushroom-shaped resin glands contain a bounty of terpenes. They are the key to knowing the plant is ready to be harvested. Grab a magnifying glass to observe trichomes and tune in to the plants.

Some growers still use the pistil method. The pistil color can also indicate that cannabis flowers are nearing optimal THC and CBD levels, but trichomes are more accurate. Start checking in regularly once white hairs start to turn orange.

“Resin glands change colors as they ripen. At first, glands are clear. As they continue to mature, they turn a translucent milky color and, finally, they turn amber,” Cervantes writes in Marijuana Horticulture.

He uses a 30x hand-held microscope with a battery-powered lamp to observe the glands carefully as they turn. The master grower recommends harvesting weed when resin glands have turned from clear to translucent with a few milky white heads throughout. Those early to harvest will miss out on some valuable resin production.

Rosenthal agrees with this sentiment, adding that aroma grows stronger as the process happens.

“The odor reaches its peak at the same time the trichomes begin to fluoresce in the light, twinkling like little crystals,” Marijuana Harvest states.

when to harvest marijuana: two people harvest outdoor plants

What are trichomes?

Trichomes are resinous glands that grow on many plants like tomatoes and cannabis. They are responsible for much of the aroma a plant gives off and much of the crystal matter that makes up kief. This is due to the trichome heads containing most of the terpenes and cannabinoids found in cannabis flowers. In fact, the trichome colors changing is a sign that the compounds are ripe.

“These colors indicate that THC is beginning to degrade into two other cannabinoids, cannabicyclol (CBL) and cannabinol (CBN), which are not nearly as psychotropic as THC,” the authors write in Marijuana Harvest.

Cervantes continues on the topic, describing the anatomy of a trichome.

“The highest concentration of THC is located at the base of the resin head.”

Trichome color and shape are key indicators to harvest marijuana plant flowers, but that’s not all to keep an eye on. Trichomes and buds all mature on their own timeline. Top buds are generally ready to cut before flower growing on the sides or bottom of the plant.

In the same way, trichomes get sparkly whenever they feel like it. That is why Cervantes and Rosenthal recommend waiting for all heads to turn translucent and a few to become milky white. This is the best time to maximize ripeness of the most glands possible without letting too many trichomes degrade. When they become amber, it is a sign that terpenes, THC, and CBD are losing steam.

Harvesting at the right time means maximizing terpenes and cannabinoids. That is why it is essential to keep a close eye on plants rather than only trust timetables.

Interesting facts about ripening cannabis plants

There are some interesting facts about cannabis as it gets ready for harvest. For example, some indica strains, like Blueberry, have special trichomes. Instead of milky white, these resin glands take on a purplish hue.

Rosenthal and Downs share some ripening facts in Harvest Marijuana. If plants are cloned from the same mother and grown in the same environment, they are most likely to flower simultaneously. This means growing from seed will have more harvest timing variance than gardens filled with clones.

Another way to get all the buds to ripen evenly is to use cultivation methods that optimize how light hits the flowers. If the plant receives equal light from every angle, they are more likely to ripen evenly. Those growing outside will want to space plants out to provide them up to three angles of sunlight as the season ends.

Cervantes also shares that though many prefer to pluck fan leaves off during flower, leaving foliage on the plant does no harm. However, if leaves remain yellowing and unhealthy despite nutrients and amendments, pull them to preserve plant health and keep energy moving toward the flowers.

The final word on when to harvest marijuana plants

Growing cannabis is a labor of love. It’s hard work and can be a visceral experience. Hands in the soil (or other growing medium) and gardens wafting with dankness guide a person to be present. A presence of mind is required to know when to harvest cannabis.

There are signs and timelines that indicate a plant is ready to be harvested, but the key indicator of whether cannabis flowers are ripe lies in the trichomes. Like much of the process, this is not a cut-and-dry situation. It requires tuning into the garden.

Trichomes and cannabis flowers develop on their own time. If the genetics indicate flowering should commence, but the trichomes aren’t sparkling: a grower is best served trusting their eyes over their prospected schedule.

With a magnifying glass and these excellent books that should grace every enthusiast’s library in hand, any level gardener has the tools to harvest cannabis flowers at the optimal time.

Cara Wietstock is Senior Content Producer of GreenState.com and has been working in the cannabis space since 2011. She has covered the cannabis business beat for Ganjapreneur and The Spokesman Review. You can find her living in Bellingham, Washington with her husband, son, and a small zoo of pets.