How to Harvest Weed by Ed Rosenthal exclusively for Stuff Stoners Like.
Harvesting marijuana, drying it, curing it and storing it are processes incredibly important to marijuana growers. Each step contributes to the final quality of the flowers. A good crop followed by a poor harvest is as disastrous as crop failure. It’s post-crop failure.
Growers usually plan their gardens in great detail and carefully bring the plants to the peak of maturity. However, they often spend a lot less time planning how to harvest weed. 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.
Harvesting cannabis: the basics
The harvest 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. How to harvest cannabis involves multiple steps done in a specific order: cutting down plants, their colas or buds, removing their leaves, then drying, curing and storing for later use or for processing into buds, extracts, edibles and other products.
Important decisions about how to harvest weed include when to cut the crop, whether to cut whole plants or to judge each bud for its ripeness, when to trim, how and where to dry and cure the buds, and how to preserve the aroma and taste by retaining the terpenes and essential oils, which can evaporate in temperatures as low as 68° F (20° C).
On a small plant, all the buds will likely ripen at the same time. On larger plants, the outermost exposed parts of the buds, the first 3–6 inches (7.5–15 cm) may ripen before the inner buds. Different varieties have unique ripening patterns. In a garden of mixed varieties the ripening times may vary by several weeks.
The cannabis plant grows vegetatively for several months before starting reproductive growth (or flowering). It begins flowering when it receives at least nine to eleven hours of uninterrupted darkness each 24-hour period. Outdoors in the northern hemisphere, flowering usually begins between late July and September, and ripening between September and November. Using light deprivation, some outdoor growers manipulate the light cycle to harvest in the summer. Indoor growers control flowering by adjusting the light regimen. Flowers reach peak potency in seven to ten weeks.
When is weed ready to harvest?
Begin planning how to harvest weed when the flowers ripen—six to eight weeks after the beginning of flowering. No bud should be picked before its time. Plants and varieties differ in maturation pattern. Some mature all at once, so that the whole plant can be picked. Other varieties mature from the top down, or from the outside in. For these varieties, the buds on the outside mature faster than inner buds hidden from the light. Once the outer buds are harvested, the inner branches are exposed to light and quickly ripen. It can take two weeks of choosing mature buds before the plant is totally picked. Picking the plant a little at a time ensures that every bud is at maximum potency and quality.
The best way to determine when to harvest weed is by watching the development of the trichomes (the stalk-like resin glands that contain the active compounds), which grow on the leaves surrounding the flowers. The flower area becomes covered with resin glands over time. This stage of growth usually lasts two to three weeks; in modern varieties these glands ripen in seven to nine weeks from flower initiation. Late-season and long-maturing varieties usually spend about three to five weeks in this period of heavy trichome growth.
As marijuana flowers near ripeness, their caps swell with resin and the trichomes become more prominent and stand erect. The viscous, sticky liquid that accumulates contains terpenes and cannabinoids, which are produced on the inside membrane of the trichome cap. As the resin accumulates in the cap, the flower odor becomes more intense. The odor reaches its peak at the same time the trichomes begin to fluoresce in the light, twinkling like little crystals. In some varieties, the trichomes are so prominent that the whole bud sparkles.
Using a magnifying glass, a photographer’s loupe or a microscope, monitor the buds’ progression to the peak of ripeness by watching the resin in the gland tops. Under magnification, you can see individual glands turning from clear to amber or a cloudy white. 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. When the trichomes begin to change from clear to amber or cloudy white, the buds should be harvested—this is the peak moment.
Before the weed harvest, flush or leach outdoor plants for 10 to 15 days. Don’t water for one to two days before harvest—the water is only going to have to be dried out later. Over fertilized, unflushed buds leave a harsh chemical taste on the roof of the mouth and upper throat.
Harvesting weed early or late
Many growers determine when to harvest pot based on the 30/70 rule. They harvest when approximately 30% of the trichomes have turned amber and the remaining 70% are milky white. By this time much of the THC has degraded to CBN and has lost potency.
So how to harvest cannabis for the most potent buds? As soon as the first trichomes turn amber or white, the pot is ready for harvest. How to harvest weed to treat insomnia is to pick it later than usual—CBN, the desired cannabinoid, develops when the bud is over-ripe. Some growers assume how to harvest weed for higher BCD levels is to harvest early. This is not true. Harvesting early, under-ripe buds only produces an end product with less overall cannabinoid content. Cannabis will not continue to ripen after it has been harvested.
Marijuana harvesting strategies
Before laying out a strategy for how to harvest weed, determine your garden’s goals. If the crop is to be used for its flowers, how to harvest weed is different than for extracts and concentrates. As with any blooms, cannabis flowers should be handled gently and with care. Plants used for extracts or concentrates can be handled without concern for cosmetic beauty.
Harvesting pot can be done over a longer period of time by a smaller group of people, or in a shorter time by a larger group. A smaller group can more easily handle a crop harvested over several weeks versus a crop harvested all at once. Whether you are solo or have a harvest team, make a plan for how to harvest weed that divides up the tasks so there are few bottlenecks. For instance, if you have access to an area to store branches or colas but insufficient trimming facilities, prioritize bringing in the buds and pulling off fan leaves; the colas can be placed in storage to dry before trimming, or under refrigeration to keep them fresh for wet trimming. Then the material can be manicured over a longer period of time.
Varietal differences in ripening time
Each marijuana variety has an expected ripening time. When a single variety is grown, all the plants will have ripe buds at the same time. When several varieties are grown, how to harvest weed is different because varieties could ripen every few days for a month or longer. Large sativas and sativa hybrids often have buds more than 1 foot (30 cm) long. Sometimes the outer 6 inches (15 cm) are ripe, but the inner portion is not because it was partially shaded by the branch above. Cut the ripe portion and leave the unripe. Once the inner portion is exposed to more direct sunlight, it will ripen in a week or less.
Whether you’re growing a single variety or several varieties with different maturation times, how to harvest weed is the same—harvest only mature buds and leave the rest. You’ll improve the quality of the crops and extend the harvesting period.
Outdoor growers can induce plants to flower early via light deprivation. Plants are placed under the sun but receive only twelve or thirteen hours of light daily and eleven or twelve hours of uninterrupted darkness from shade curtains. This causes the plants to flower, no matter their size or age. With the use of light deprivation, ripening can be timed for early harvesting, to avoid fall weather, or to produce multiple harvests.
A grower needn’t build a greenhouse. Plants in containers on rollers can be moved around with the sun and brought indoors when it is time for darkness. Some growers use hoops draped with white-black panda plastic to create darkness. The white color on the outside reflects light and prevents heat buildup, keeping the plants cool. The black on the inside prevents light from reaching the plants, extending the dark period necessary to induce flowering.
Marijuana is a fall-flowering plant. At the time when plants could use more light energy, energy of sunlight is naturally declining, from August through Autumn. At the same time the weather may change from balmy summer to cool fall, sometimes with wind and rain—weather not always conducive to great buds. A grower may have to make hard decisions and compromises.
Consider the following situation: the buds are ten days from early ripeness. The weather forecast is for cool weather followed by rain and then a long period of sun and warm weather, long enough to ripen the crop. How to harvest weed in this case? Cut early and forfeit ripeness, or leave the plants standing and take measures to try to prevent mold attacks?
What to harvest
Large plants: A large marijuana plant, whether tree-like or bushy, that has basked in the sun all season may be covered with colas from top to bottom. Every area kissed by the sun has branches with leaves and buds to capture the light. Remember, however, that the buds occupy only the perimeter of the plant. The interior is made up of bare stem and a framework of bare branches supporting the vegetation. You have a few choices for how to harvest weed here: cut the whole plant or big sections of it; cut individual branches; cut just the ripe buds and leave the rest to ripen; or cut all the buds, separating them into A’s for ripe and B’s for premature.
Let’s look more closely at these options for how to harvest weed. Why would a grower consider cutting the whole plant? Perhaps weather conditions are severe enough to require a rapid harvest. Or if the grower has a crop that ripens evenly and is ready to harvest at the same time, s/he may choose to cut whole plants in order to harvest the entire crop at once. How to harvest weed may revolve around labor availability. A grower can choose a large crew to cut and dry the product all at once, a surge crew to work for a limited period of time, or, depending on financial constraints, a crew to trim when demand for labor is lower.
Another choice for how to harvest marijuana is to cut individual branches as they mature. Cutting off the outer branches opens the inner buds to light, hastening maturity and providing more light to the undeveloped sections. A grower may trim individual buds for the same reason—doing so provides the immature buds more light.
But other factors may lend themselves to harvesting only the buds. If the weather is predicted to stay fair for a long period, a grower may choose to change the harvest flow by slowing the process down and trimming off the best buds as they become perfectly mature.
You may choose to sort buds or branches into A’s and B’s, using the material for different purposes. If you are feeding a machine, cutting individual branches is often preferable. Before using the trimming machine, separate the perfect buds from lesser quality buds. The shake and imperfect buds are used for concentrates while high-quality buds are trimmed.
Small plants: With smaller plants, often most of the buds are ready at the same time. How to harvest weed is simpler here—the whole plant can be cut at the stem, or the colas can be cut. All material removed from the plant should be placed on tarps, in bags or in plastic bins for transfer to the processing space.
Over-ripe flowers can be identified in several ways. First, the trichomes turn color as the resin they contain degrades from THC to CBN. Sometimes new white stigmas grow from the buds. Over-ripe buds grow “bananas,” single male flowers that take the shape of the yellow fruit. They form late in the growing cycle so any pollen they produce will not affect the flowers. But cosmetically they are disastrous; they drastically reduce a bud’s value.
Over-ripe flowers do have a use. They produce all-female pollen, meaning any seeds will be female. They produce all-female pollen, meaning any seed produced will be female. Some high-CBD/THC strains reach peak CBD levels earlier than THC levels. Let them fully ripen to increase THC levels.
Buds infected with powdery mildew or other molds and fungi are unfit for smoking. Many jurisdictions mandate laboratory testing of commercial cannabis for fungal and bacterial pathogens. Moldy buds are not suitable for use in extracts either; concentrating contaminated cannabis transfers toxins and spores into the final extract. Moist hash will mold when stored at room temperature. Butane and carbon dioxide extractions kill mold and mildew but leave toxins behind. As a result, professional extractors in legal states are facing mandatory lab testing.
Botrytis (gray or brown mold) is found almost everywhere and infects many plants, including marijuana. The fungus, which germinates only on wet plant tissue when the temperature is 55–70° F (13–21° C), consumes the plant, both live and drying buds. Mold grows when buds are grown or dried in an environment that is too humid, or when incompletely dried buds are sealed in airtight containers. Once mold starts growing, it tolerates a wider range of humidity and temperatures.
How to harvest weed best without mold is to prevent mold from forming. Wet marijuana is 80% water. Mold spores colonize plant matter that contains as little as 15% water, so it’s important to dry quickly, and in as controlled a fashion as possible without sacrificing terpenes. Keep humidity under 50%, and don’t raise the temperature above the low 70s. Low-humidity air is not saturated and absorbs moisture faster.
Mold and fungal spores are mobile; they are in the air and on surfaces. To germinate they require 60–75° F (15.5–24° C), high humidity and an acidic environment. Keep humidity below 50% and the leaf surface alkaline to prevent mold spores from germinating. When the cannabis plant is alive, its natural defenses fight off constant attacks by pathogens. As soon as the plant is harvested, it is very vulnerable to molds.
Photo credit: Top pic by Ed Rosenthal, Mid pic by David Downs. Bottom pic by Ed Rosenthal