After the cure, the way you store flower decides how long it keeps its potency and aroma. This part covers containers, humidity packs and desiccants, cold storage, trim, bulk stock, stock rotation, a testing schedule and the Thai rules. It ends with a storage plan for every scale, from a home grower to a large farm.
Here is a short summary of why storage matters. Light, oxygen, heat and the wrong humidity each damage dried flower. THC slowly turns into cannabinol (CBN), which is the main chemical sign of ageing. Aroma compounds (terpenes) evaporate.
The safe moisture range is a water activity (aw) of 0.55–0.65. Water activity runs on a scale from 0 to 1 and shows how much of the water in the flower mould can use. For cured flower, a jar relative humidity (RH) of 58–62% gives roughly this range. Curing itself is covered in Drying & Curing.
This is Part 2. Part 1: Storage: Humidity, Light, Oxygen, and Shelf Life
Containers: glass, plastic and vacuum bags
Glass is the standard. It does not react with the flower, gases cannot pass through it, and it releases no plasticisers. Plasticisers are chemicals added to many plastics to make them soft. Ordinary mason jars are made of soda-lime glass, the everyday kind, and they work perfectly well. Wide-mouth jars with tight-sealing lids are the most practical choice.
Plastic lets oxygen through slowly. This includes polyethylene and polypropylene, the plastics used for most bags and food tubs. Plasticisers can also move into resinous material. Plastic is fine for a few days, but use glass for anything longer than about two weeks.
Vacuum bags remove most of the oxygen. However, they squeeze the flower, which can damage the trichomes. Trichomes are the resin glands that hold most of the cannabinoids and terpenes. Oxygen also still passes slowly through the bag. One option is to vacuum-seal the flower and keep the bag inside a glass jar or an opaque box.
What to do: test each jar’s seal before you rely on it. Seal a hygrometer inside a jar of flower for a few days. If the reading moves toward the humidity of the room, the lid leaks and should be replaced.
Nitrogen flushing: replacing the oxygen
Nitrogen flushing pushes the air out of a container and replaces it with nitrogen. Nitrogen is an inert gas, which means it does not react with cannabinoids or terpenes. Removing the oxygen slows the change of THC into CBN and the oxidation of terpenes. Flushing is standard for foods that oxidise easily, and it works the same way for cannabis.
It is worth doing in two situations:
- Stock kept longer than about six months. Nitrogen flushing and frozen storage are the two options here.
- Bulk bags kept longer than about 60 days. Here nitrogen flushing is preferred over vacuum sealing.
Flushing at scale is practical and cost-effective. Small flushing kits exist, but how well they seal varies.
Translator’s note: in Thailand’s heat, the benefit is slower ageing during long storage. Start with a small trial. From one lot, flush and seal a few bags, and keep a few unflushed bags beside them. Test both at 90 and 180 days (see the testing schedule below) before you change your whole process. When you buy the gas, ask the supplier for food-grade nitrogen.
Two-way humidity packs
Two-way humidity packs for flower come in set levels. Boveda is commonly used at 58% or 62%, and Integra Boost comes at 55% or 62%. They keep a sealed container close to that RH by absorbing or releasing moisture. Inside each pack is a proprietary salt formula behind a semi-permeable membrane. The membrane lets water vapour through but not liquid water.
Their limits:
- They hold only a limited amount of moisture. They cannot rescue flower that is under-dried or too wet. Flower must be correctly dried and cured before you seal it with a pack. In a jar of over-wet flower, the pack quickly fills with moisture and the jar stays above the target.
- They control humidity only. They do nothing about oxygen, light or temperature.
- They cannot make up for a bad seal. In the Thai rainy season the air is often at 75–90% RH. A poorly sealed container keeps letting moisture in. Check that seals are tight instead of assuming they are.
Translator’s note: to buy packs, ask the official distributor in Thailand of the brand you want, or ask other members in Equipment and Supplies.
What to do: use a pack to keep correctly cured flower stable, not to fix wet flower. If a jar with a pack still reads above 62% RH after a day or two, the flower was sealed too wet or the lid leaks. Take the flower out and dry it further.
Silica gel and sealed boxes in the rainy season
Translator’s note: the original article does not cover silica gel. The advice below is general practice for storing flower in Thai and Southeast Asian weather.
Silica gel and similar desiccants (drying agents) only absorb moisture and never release it. Unlike a two-way pack, they do not stop at a set humidity. If silica gel is sealed in a jar with flower, it can dry the flower below aw 0.55. Below that level, flower turns brittle and loses aroma.
A safer setup for the rainy season uses two barriers:
- Seal the flower in glass jars. Add a two-way pack to each jar if you use them.
- Put the jars inside a larger airtight box, such as a food storage box with clip-down lids.
- Put silica gel in the box, outside the jars, with a small hygrometer.
The gel keeps the air around the jars dry. If a jar leaks slightly, it takes in dry air from the box instead of humid room air. When the box hygrometer starts to rise, the gel is full. Replace it, or dry it again following the maker’s instructions.
Cold and frozen storage
The Q10 rule from Part 1 says reaction speed roughly doubles with every 10 °C rise. By that rule, flower at 15 °C degrades about half as fast as flower at 25 °C. For stock kept a year or longer, a wine cooler or a dedicated cooled cabinet is a worthwhile upgrade.
Freezing greatly slows chemical reactions, including reactions driven by the plant’s own enzymes. It does not stop them completely. The drawback is that trichome stalks become rigid when frozen. Handling, shaking or the shrinking of material as it cools can snap the trichome heads off.
To freeze flower safely:
- Freeze only flower that is already at aw 0.55–0.65.
- Use airtight containers, preferably glass, with little headspace (empty air inside).
- Handle the flower as little as possible until it has warmed up again.
Ice-water extraction uses this brittleness on purpose to knock trichomes off the plant material. In storage you want the opposite. Commercially, vacuum-sealed frozen storage is used for flower that will be processed later.
Opening cold containers without wetting the flower
When you open a cold container in warm, humid air, water condenses on the flower. It is the same thing you see when a cold drink can sweats on a table in Thai weather. The water comes from the air, not from inside the jar.
The dew point is the temperature at which moisture in the air turns into liquid water on a surface. At 30 °C and 85% RH, the dew point is about 27 °C. Any surface cooler than that collects water. A jar straight from a 5 °C refrigerator is far below the dew point. The water on the flower can push its surface aw above 0.65, the level where mould can grow.
Follow these steps for refrigerated or frozen stock:
- Move the sealed containers from cold storage to a space at 15–20 °C for at least two hours.
- Open them only when the outside of the container has reached room temperature. It should feel warm, not cold.
- If the air is above about 80% RH, open them in an air-conditioned room or wait for a drier time of day.
These steps work because the flower warms up while it is still sealed. When the container no longer feels cold, its contents are no longer cold enough to collect water.
Storing trim before extraction
Translator’s note: the original article does not discuss trim. The points below apply its storage rules to trim. Post questions about other cases below this topic.
- Mould. The same limit of aw 0.65 applies. A damp pile of trim in a bag during the hot rainy season is at high risk. Dry trim to aw 0.55–0.65 before you bag it, or keep it cold.
- Headspace. Trim is loose and leafy, so a bag of it holds a lot of air. As explained in Part 1, loose material loses aroma faster. Fill containers well and seal them.
- Light, heat and oxygen. Keep trim dark, cool and sealed, the same as flower. Vacuum-sealed frozen storage matches commercial practice for material that will be processed later. Ask whoever will do the extraction what condition they need the trim in.
- Rotation. Label each bag with its lot ID and date, and process the oldest first.
From 26 April 2026, the Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569 applies. Licences for extracts above 0.2% THC are granted only to Thai juristic persons that are not “foreign” under the Foreign Business Act B.E. 2542, to state agencies and to the Thai Red Cross Society. Before you store trim for extraction, confirm who will hold the extraction licence.
Bulk commercial storage
When stock reaches hundreds of kilograms, individual jars stop being practical. Bulk stock is stored in three ways:
- Food-grade mylar bags of about 250 g–1 kg each, flushed with nitrogen, heat-sealed and packed in boxes. Mylar is a metallised plastic film that blocks light and lets very little oxygen through. These bags are standard in the dried-herb and spice trade.
- Vacuum-sealed food-grade bags for shorter storage before processing. For storage beyond about 60 days, nitrogen flushing is preferred.
- Climate-controlled storage rooms at about 15 °C and 55–62% RH, with no UV sources. They are built like pharmaceutical and food cold rooms, with continuous temperature and humidity logging and backup power.
Give every lot a batch ID that traces back to its harvest and drying cycle. Record its harvest date, cure-completion date and storage conditions. Set an internal quality-review date for each lot based on your own test results.
Translator’s note: licensed operators in Thailand already have to keep certain records (see Licence Holder Duties in Thailand). Keep your storage records next to those records, so one batch ID connects the harvest, the stock records and the test results.
Rotating stock: oldest out first
Use first in, first out (FIFO) rotation. Older stock that ends up behind newer stock is always used last, so it degrades the most. Several measures prevent this:
- Bins stamped with dates.
- Clear rules on who takes stock out, and from where.
- A written SOP (standard operating procedure) for receiving, testing, labelling and rotating stock. An SOP is a set of step-by-step instructions that staff follow every time.
What to do: write a one-page SOP for your storage area this month, and train each person who takes stock out. Its purpose is to ensure no lot sits forgotten at the back while its THC turns into CBN.
Testing schedule to check that storage is working
The tests below use standard laboratory methods. HPLC (high-performance liquid chromatography) measures cannabinoids without heating the sample, so it reports THCA and THC separately. GC-MS (gas chromatography–mass spectrometry) separates and identifies volatile compounds such as terpenes. A microbial screen is done either by culture (growing microbes from the sample) or by PCR, a DNA-based test that detects specific microbes. Results come on a certificate of analysis.
- When the cure is complete (day 30–60): full cannabinoid panel (HPLC), total terpenes (GC-MS), water activity and a microbial screen (culture or PCR). These results are your baseline.
- At 90 days: THC, CBD and CBN, a terpene spot-check for monoterpene loss, and a visual check for mould.
- At 180 days: repeat the full baseline panel. Compare CBN with the baseline. A rising share of CBN is the clearest chemical sign of oxidation.
- At 12 months: full panel plus a sensory evaluation, meaning a structured check of smell and appearance. Set your own internal limit for terpene loss. For example, you could flag lots that have lost more than about 30% of their baseline terpenes. This figure is only an example, not an industry standard.
This is how a commercial grower sets shelf life. The baseline shows where the lot started, and each retest shows how fast it is changing under your storage conditions.
Translator’s note: not every laboratory in Thailand offers every test in this schedule. Before you send samples, ask whether the lab can run terpenes, water activity and a microbial screen. The forum guide on testing at Thai laboratories is a starting point. You can also ask other members in B2B Services. Home growers do not need lab tests. A hygrometer in the jar, a dated label and a smell note each time you open the jar give a rough version of the same check.
Thai rules for storing flower
In Thailand, cannabis flower is a controlled herb. This status comes from the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568, issued under the Thai Traditional Medicine Protection Act B.E. 2542. It has been in force since 26 June 2025. It is supervised by the Department of Thai Traditional and Alternative Medicine (DTAM) under the Ministry of Public Health. The rules for flower are:
- Flower may be sold only against a PT 33 (ภ.ท.33) prescription from an authorised practitioner, covering at most 30 days.
- Advertising and online sale of flower are prohibited.
In 2026, two Ministerial Regulations of B.E. 2569 tightened licensing. The Regulation on Cannabis or Hemp Extracts came into force on 26 April 2026. The Regulation on Controlled Herbs (No. 2) came into force on 30 April 2026 and tightens the licence criteria for cannabis flower. The draft Cannabis Control Act is not law yet. The Cabinet approved the draft on 22 September 2026 and sent it to the House.
A business that sells or processes flower, at any of the scales in this guide, needs a licence for that activity. Check the current labelling and record-keeping requirements with DTAM and the Ministry of Public Health.
Translator’s note: under Section 78 of the 1999 Act, selling or processing a controlled herb without a licence carries up to 1 year in prison and/or a fine of up to 20,000 baht. Before you store flower or trim in commercial quantities, check which licence covers your activity in Licensing and Compliance in Thailand.
This guide is for education only. It is not advice to buy or sell cannabis flower. Anyone growing at home in Thailand should check the current rules with DTAM.
Storage plan in summary
| Factor | Target |
|---|---|
| Temperature | 15–18 °C. Use a refrigerator only if you follow the steps for opening cold containers |
| Water activity / RH | aw 0.55–0.65; jar RH 58–62% |
| Light | Complete darkness |
| Oxygen | Little headspace; nitrogen flushing or vacuum for long storage |
| Container | Sealed glass kept in the dark, or opaque nitrogen-flushed bags |
- Check that aw is 0.55–0.65 before sealing. For small batches, the RH reading in a sealed jar is a usable substitute.
- Use amber glass jars with tight lids. Add a two-way humidity pack if you want one.
- Store the jars in darkness at 15–18 °C.
- Open containers as rarely as possible, because every opening lets in room air.
- For storage beyond about six months, consider nitrogen flushing or frozen storage, and follow the steps for opening cold containers.
- Label every container with the cultivar, lot ID, harvest date and cure-completion date, and use the oldest stock first.
By scale:
- Home grower (grams to hundreds of grams): amber jars with a 62% two-way pack, kept in the coolest dark cupboard. Avoid the refrigerator unless you follow the steps for opening cold containers. Expect about six months of good quality.
- Small commercial (kilograms): a dedicated room with a split-unit (wall-mounted) air conditioner at about 18 °C. Add a data-logging hygrometer, which records readings over time. Test aw before sealing flower for long-term storage.
- Medium (tens of kilograms): a cold room at 15 °C and 58–62% RH. Use nitrogen-flushed opaque bags for anything kept beyond 60 days. Run the full testing schedule and rotate stock strictly, oldest first.
- Large (hundreds of kilograms): duplicate temperature and humidity control systems, so one can take over if the other fails. Add continuous logging, formal SOPs and nitrogen flushing at scale.
Share your setup
Post your storage setup below this topic. Say where you keep the flower, the temperature and RH you measure, and how long it kept its aroma. Growers in the same climate can compare results and spot problems early.
References
- ASTM D8197-22: water activity range of 0.55–0.65 for stored dry cannabis flower.
- The storage studies cited in this guide (Zamengo et al. 2019; Taschwer & Schmid 2015; Lindholst 2010; Jaidee et al. 2022; Bini et al. 2024) are listed with full citations and DOIs in Part 1: Storage: Humidity, Light, Oxygen, and Shelf Life