What exactly to do after harvesting cannabis

What exactly to do after harvesting cannabis? Explore the pitfalls of post-harvest storage and processing, drying and ripening of cannabis flowers.

Storage after harvesting cannabis

The quality and potency of marijuana changes over time. In the living plant, the precursors of THC and CBD are present in their acid forms, THCa and CBDa. These are not psychotropic. Only when they lose some of their molecules do they become active as THC and CBD. This happens naturally over time and is accelerated by heat and light, especially ultraviolet light.

Once the flowers are dried and cured, the potency is at its peak. Over time, THC is gradually broken down to CBN, a far less psychotropic cannabinoid than THC. Research conducted at the University of Mississippi on low-grade cannabis stored at room temperature (20-22 °C) for four years found that the percentage loss of THC is proportional to the length of storage, with the loss being greatest in the first year. While the THC content decreases, the CBN concentration increases.

schelude of THC cannabinoids loss over the 4 years

This research is consistent with the experiences of marijuana users. Marijuana loses potency over time as the psychoactive THC converts to CBN, which induces sleep but no high. Storing flowers in the freezer or refrigerator slows the deterioration. Freezing keeps the flowers fresh the longest. But even then, the THC content decreases at almost 4% per year. In the freezer (below 0°F), the decay slows down further. At refrigerator temperatures, the THC content decreases by about 5.4 % per year. A freezer is best for long-term storage; a refrigerator is good for short-term protection of the terpenes. There are several problems with storing marijuana in the freezer, especially if it is subcooled to -18°C.

Even at higher temperatures in the freezer, the glands become very brittle and can be easily and accidentally shaken off the flowers. For this reason, the container should be handled very gently after placing it in the freezer, and after removal the flowers should be given time to warm up so that they become more pliable.

The moisture in the container will freeze and may form ice crystals, especially if stored for a long time. This can also occur if the flowers have not been sufficiently dried.

However, several experiments showed that properly dried marijuana in a plastic container did not form ice crystals when stored in the freezer for several months. The trichomes remained intact. If humidity is a problem, vacuum sealing largely eliminates it, although the process can result in crushed flowers. Another solution is to remove the air with moisture-free gas such as carbon dioxide or nitrogen. These gases can be injected into the container while the ambient air escapes through another hole. Both holes are then sealed.

If you freeze marijuana in glass containers, choose shoulderless containers, as containers with shoulders are more likely to crack. Metal and wooden containers can also be used for freezing.

One way to store frozen marijuana is in small containers. Only pack as much as you need for a week in each container. The rest of the stored material will not be touched, so the glands are not at risk as they can be taken out of the freezer individually.

According to the University of Mississippi study, refrigerator temperatures slow deterioration to a little less than 0.5 per cent per month, which is not noticeable when stored for only a few months. Again, it is best if most of the stored material is stirred infrequently.

Heat and light, especially UV light, cause terpenes to evaporate and affect the quality. Only an opaque container will fully protect the terpenes and thus the quality of the flowers stored in it. An opaque container with a white exterior reflects heat and keeps the contents cool. Using a desiccant pack that maintains a certain humidity of around 60-65 per cent ensures that the right level of moisture is maintained without causing mould.

Terpene molecules vary in size, and the smallest ones evaporate at lower temperatures, starting in the 60s. Flowers stored at room temperature in an open container will lose some terpenes. If you store flowers in the fridge or freezer, the terpenes remain in a liquid state and do not gas out.

Storage containers material for cannabis

Storage containers material for cannabis

Cannabis can be stored in a number of different materials, each with advantages and disadvantages that make them more or less suitable depending on the grower’s needs.


Glass is a great, inert, hard, non-biodegradable storage container. The downside is that most glass jars are transparent and light will break down the trichomes – but this doesn’t matter if the flowers are stored in the dark. Opaque glass is best for storing flowers exposed to light. Different types of glass are used for food storage. The colour of the glass determines the type of light and heat that can penetrate the barrier.

Violet glass

Violet glass blocks visible light except for the colour violet. It is also semi-transparent to UVA, an infrared light, and transmits about 40 to 60 per cent, depending on the composition and thickness of the glass.

Miron Glass, a manufacturer in Germany, claims that this combination of light preserves biological material such as herbs and fresh vegetation. The company loosely bases its claims on bio-photons, which is very weak light emitted by all living things.

The literature claims that the light entering the glass preserves this energy while providing a barrier to other visible spectra that can cause the decay of cannabinoids and terpenes, even when the material is dry.

Placing a glass or stainless steel container in a dark space such as a fridge or dark room will also keep out harmful light. It is very unlikely that there is much UVA light indoors, so none gets through. Visible light, however, is filtered out.

In a controlled experiment, fresh garden tomatoes were placed in a miron container, a stainless steel container and a clear glass container. All were sealed and the clear glass container was kept completely in the dark.

When the jars were opened a month later, the tomatoes were still fresh, if a little dried out. The containers were resealed and opened again a month later. All three tomatoes had started to mould to a similar extent.

Stainless Steel

Stainless steel containers with plastic seals and flip-top lids are popular because they are stable and stackable. The metal does not react with flowers and is not sensitive to the outside air. Stainless steel containers are an excellent choice for storage.


Cannabis is slightly acidic and lipophilic, so it breaks down some plastics. Plastics are stickier than glass or stainless steel. Odourless turkey bags are popular because they trap odours well and are cheap. However, they are easily punctured by stems and offer no protection from shaking and movement, causing further damage and shock. Five-gallon buckets sealed with toothed, airtight lids protect flowers from being crushed and can be stacked.

Vacuum Sealing

Vacuum packing is popular because it reduces the amount of oxygen in a storage container. Oxygen is corrosive and affects the colour of the flowers. Low oxygen also prevents the growth of spoilage bacteria, but not anaerobic bacteria. Anaerobic bacteria thrive in a low or no oxygen environment that is humid and contains food – the flowers! Never seal and store wet or damp flowers.


A desiccant is a substance that removes moisture from the surrounding air. Desiccants are often found in certain food packaging, e.g. for dried seaweed, and in electronics. Silicone packets, newspaper or other particularly dry materials act as desiccants and absorb the moisture in a storage container.

Gas-based storage

Gas-purged, sealed Mylar bags are excellent packaging for long-term storage. In this process, the bag is purged with nitrogen and sealed. Unlike oxygen, nitrogen is inert and does not burn. Removing the oxygen from the packaging extends the life of the flowers and prevents mould and discolouration, similar to vacuum sealing. Gas-purged bags are a cornerstone of food packaging and are commonly used for snacks such as chips and jerky. Some testing laboratories offer nitrogen bag services with tamper evident packaging.

Fresh-frozen storage

Instead of being prepared and dried, marijuana can be processed directly into concentrates or stored undried and frozen “wet” to be used later. This saves energy and labour. Storage allows the processing of the material to be postponed until a more convenient time. Either fresh or frozen flowers can be used for Bubble or BHO. First, the crushed flowers are brought to temperatures close to freezing. Then, the glands become brittle due to the agitation of a paint mixer or other device; they break off and are collected in a series of filters that collect glands of different sizes. The collected glands yield hashish that can be used in a vaporiser or pipe, or as an intermediate in the production of butane or C02 concentrate. BHO extractors use butane as a solvent to decannabinise and de-terpenise the leaf. The result is a very pure, dabbable concentrate.

After harvesting cannabis

After the harvest is finished, the producers are left with a variety of by-products. What used to be considered waste is now processed and enjoyed or sold. The first step is to assess and separate the material.

The most efficient way is to sort the material during pruning.

The quality of the remaining material is determined by the percentage of THC and other cannabinoids it contains. After removing the flowers, three types of growth remain: popcorn flowers (larf), sugar residue and fan leaves.

Stems and woody parts of the plant are not suitable for consumption as they contain few cannabinoids.

Grades of cannabis trim

Grades of cannabis trim


Flowers that receive less light become smaller and less dense. They are time-consuming to trim and cosmetically undesirable on the market. However, they contain a high percentage of THC and are often used to make pre-rolls or concentrates.

Sugar trim

Sugar trim refers to the resin-covered leaves that grow near and often surround the flowers. They are cut off during manicuring and contain the most THC of the plant, next to the flowers. Sugar trim is used to make extracts such as kief, hash, tinctures and edibles.

Fan leaves

Although fan leaves contain a third or less of the cannabinoids than sugar trim, they can still be worth processing. Leaves with visible glands are worth keeping. Leaves from immature plants usually have very few glands and do not yield much THC.

Use a magnifying glass or photographic loupe to view the material up close. Fan leaf glands are often small and hug the leaf surface, while glands near the flowers are stalked and look like mushrooms with bulbous caps. The latter contain much more cannabinoids than the smaller glands.

The male plants also contain cannabinoids. These cannabinoids are strongest in the pre-flowering phase. The sugar leaves – small leaves near the flowers – are the strongest, followed by the younger and then the older fan leaves. Male plants are not valued for resin production and are often removed from the garden and destroyed.

  • To use the fan leaves in cooking, heat them lightly in butter or oil. Use the infused oil in salads or cooking.
  • Grind dried fan leaves into fine flour and replace a small part of the normal flour in recipes. To remove the chlorophyll flavour, soak the leaves in cold water before drying and grinding. The flour can also be used to make ointments and poultices; a simple method is to mix it into an existing ointment.
  • Juice the fresh leaves. Rinse them first and then run them through a wheatgrass juicer. To store the juice for later, put it in ice cube trays and freeze it. The juice is used as a remedy and for general health care.

Stems and branches contain little to no usable THC. However, there are several ways to recycle them :

  • Chop and use as mulch
  • Use as kindling
  • Carve large logs
  • Use as walking sticks
  • Use for craft projects such as paper making
  • Chop finely for high quality horse bedding or small animal bedding

There are several ways to use the separated trim and maximise the value of the crop. Trim, sugar leaves and popcorn flowers can be processed into kief, hash, BHO, tinctures and edible oils.

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Published by Sakul


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