A lot can happen to a cannabis crop if it isn't properly harvested, dried, and cured. When overexposed to air, light, or heat, terpenes can vaporize or evaporate and cannabinoids can decarboxylate, which can lead to a significant drop in the potency and flavor of your harvest.
The cannabis plant's trichomes, which are responsible for producing the protective, therapeutic, psychoactive, and intoxicating properties — are at their most vulnerable come harvest time. Without proper drying and curing, your harvest can also develop mold and fungus. Knowing how to properly harvest, dry, trim, cure, and store your cannabis will go a long way in ensuring the best possible results.
Step one in reaping the rewards of your cannabis plants is knowing when they are ripe and ready for harvest. Harvesting too early will reduce your overall yield and potency, as the last two weeks of harvest are the peak time for cannabinoid production. Yet harvesting too late can cause the trichomes to become extra-brittle when they are dried and cured, making them break off easily. Harvesting at the optimal time is crucial in ensuring you get the largest possible, highest-quality yield.
What are the signs to look for when harvesting?
As the plant completes its growth cycle, there will be many physical changes that occur. The biggest are, arguably, changing colors in the large fan leaves, a tightening of the bracts that form the colas, and a change in the color of the trichome glands. These signs can help you know when to harvest your plants:
Color change on fan leaves: During the middle of the flowering stages, the plant will naturally consume most, if not all, of the nitrogen available in the grow medium. As nitrogen is responsible for the plant's green color, the plant's leaves will turn into hues of purple, and ultimately a haylike yellow, after it's consumed most of the available nitrogen. Changing colors on fan leaves aren't enough to determine when a plant is ready to harvest, but it is the first sign that you are getting close. Once the fan leaves start to change color, start looking out for the next visible signs.
Cola morphology: When observing the size, shape, and overall look of your buds, remember that this alone is not a very reliable method for judging if your crop is ready for harvest. However, ripe buds are typically tight and firm. If your buds look overly lanky or fluffy, it could be a sign that it's too early to harvest.
Trichome gland clarity: The most reliable method for determining if your plant is ready for harvest. Most often, harvest time comes when trichomes are milky white and a few are amber. If trichomes are still clear, it's too early. Trichome clarity is a direct sign of how much resin is stored in the gland. Clear trichomes mean there hasn't been enough resin production. If the majority of trichomes are amber, the buds have overripened.
When your plant starts showing signs that it is close to harvest, it is important to flush the plant of any unused nutrients. Ideally, flushing begins two weeks before harvest.
To flush your plants, flood your grow medium with water. Wait a few minutes for the water to dissolve nutrient buildup, then add more water to flush it all out. Without added nutrients, the plant will begin to feed on what's available in the grow medium leading up to harvest. Once you've flushed your plants, you will likely see the fan leaves change color as a sign of nitrogen deficiency. Finally, give your plants one last flush the day before harvest.
Properly and evenly drying your bud will help preserve its potency, vibrancy, and color. When dried improperly or unevenly, buds can develop mold, burn unevenly, and lose fragrance or flavor. Hang-drying is the simplest and most efficient way to make sure it dries evenly, and at an optimal pace. For the best drying results, follow these steps:
- Cut the plant, either at the base or into large branches.
- Hang the plant upside down in a room with the temperature set at 70 degrees Fahrenheit, or 21 degrees Celsius, and a dehumidifier set at 50%. Check and maintain the temperature and humidity daily.
- Once the stems are dry enough to snap slightly when bent, remove them from the lines and cut them into smaller sections.
- Place those sections inside of a large tote and close it with a lid. It isn't necessary for the lid to be completely closed or sealed.
- For the first couple of days, turn over and rotate the cannabis in the totes to ensure even drying.
- Also “burp” the totes in the first couple of days by opening it and allowing fresh air to filter out the damp air inside.
It's important to avoid losing trichomes during the drying process by not letting your branches hit any surfaces while hang-drying. Contact with a surface can damage trichomes and break them off of the plant. Depending on environmental conditions, the initial drying process usually takes three to seven days.
Once your bud has been properly dried, it's time for trimming and curing. The goal with trimming is to remove the excess sugar leaves that, while consumable and excellent for making edibles or concentrates, have a lower trichome concentration than flower, and typically make for a harsher smoke.
To trim your buds, hold them by a stem and gently cut away the sugar leaves and stems surrounding them. Trim over a screen to collect trichomes that break off the plant, and handle your bud with extreme care. Try to trim the crow's feet — the leaves around the bottom of a bud — as closely as possible without doing damage. All contact with the bud can cause trichome loss or damage. Hold your plants and branches by the stem whenever possible.
Wet Trim vs. Dry Trim
Most cultivators prefer to trim their cannabis after drying. Trimming immediately after harvest is the easier method, as sugar leaves haven't dried up and closed in on the buds. Unfortunately, wet trimming also allows for more chlorophyll in the leaves, which may lead to a lingering grasslike aroma. Though more time- and labor-intensive, dry trimming is generally considered the better approach.
Curing is the final stage in the drying process, allowing for a controlled breakdown of residual chlorophyll in the colas so they are neither too moist nor too dry.
To cure your bud, place it in glass jars or a tote for about 4-8 weeks. During the first two weeks, open the containers daily and allow fresh oxygen to filter through the air in the container. Open the containers every 2-3 days in the last two weeks of curing. The curing process should be gradual to ensure a proper balance of air and moisture that will preserve fragrance and flavor.
In order to maintain the chemical profile of cannabis, the buds must be kept as close to their final condition as possible. Improper storage can lead to cannabinoid degradation, loss of terpenes, a harsh smoke, loss of trichomes when flower is brittle, and development of mold or fungus if cured flowers are overexposed to moisture. Proper storage after the trimming, drying, and curing process is crucial in maintaining the chemical integrity of your final product. Temperature, moisture, oxygen, and ultraviolet (UV) light can all have a negative effect on a bud's chemical profile.
Cannabis should be kept in a cool, dark place, preferably at room temperature or slightly below. High temperature can lead to mold and mildew, dry out your flower, and turn sensitive terpenes into vapor, which will ultimately change the effects of the flower. This is why some cultivators skip drying and make live resin extracts to preserve all the monoterpenes lost during the drying process.
If the temperature is too low, THCA would be harder to decarboxylate into THC, thereby reducing the potency of the flowers when they are smoked. It can also make the trichomes brittle on the plant, which could cause them to break off when removed from the cold environment. This isn't necessarily a huge issue, though, as those trichomes can be collected as kief and smoked.
To limit your bud's exposure to high or low temperatures, keep it inside, away from windows, and in a cool place. If you're traveling outside with your bud, consider storing it in a vacuum-insulated bottle.
Moisture is the amount of weight, as a percentage of the total weight, that is lost if the material is completely dried out. Water activity is the amount of water on the surface of the plant. Both are important factors in preserving the integrity of your bud. According to ASTM Internationals cannabis subcommittee, the amount of water activity on cannabis flowers should be in the range of 0.55 to 0.65.
The most precious cannabinoids in your bud will degrade if overexposed to heat or oxygen. THCA, for example, will decarboxylate into THC prematurely when exposed to heat, and therefore reduce bud potency. When exposed to oxygen, THC will degrade into CBN, a compound estimated to be one-fourth the potency of THC. Oxygen can also oxidize essential terpenes, leaving behind a grassy, sometimes haylike aroma.
To reduce exposure to oxygen, make sure to avoid air pockets in your container whenever possible. For example, don't use a container that holds an ounce (28.35 grams) to hold a gram of flower. Vacuum-seal your flower for long-term storage, and consider getting a hand-held vacuum pump for short-term storage. Glass jars, ideally opaque and airtight for ample cannabinoid and terpene preservation, will also make adequate short-term storage.
UV light is the biggest factor in the degradation of cannabinoids, and ultimately the shelf life of cannabis. UV light will always degrade your cannabis, so that's why cultivators are now using opaque packaging instead of clear glass. UV light is another sizable contributor to THCA degradation into THC and CBN, significantly decreasing potency before it reaches the end user. UV light will also degrade CBD.
To avoid cannabis degradation from UV light altogether, use opaque packaging or brown glass bottles to store your weed. Brown bottles allow 30% of UV light to pass through, as opposed to green and clear bottles which allow 70% and 100%, respectively.
Properly harvesting, drying, and curing cannabis is a dedicated practice that takes trial and error for home growers and professional cultivators alike. But the extra care is worth the time it takes to master these steps and preserve the integrity of your flower.