A certificate under Good Agricultural and Collection Practice is not a reward for growing well. It shows that every action on the crop was written down when it happened. It also shows that an outsider, such as an auditor or a buyer, can check those records years later.
This part covers the standard itself, the records it requires, staff, the farm site, planting material, crop records, pest control, and harvest and drying. Part 2 covers storage, laboratory testing, release, audits and the Thai rules.
1. What the Standard Is and Where It Comes From
Good Agricultural and Collection Practice, usually shortened to GACP, is a quality system for medicinal plants. It covers plants that will become the raw material for medicines. For every batch that leaves your farm, it asks three questions. What exactly is it? Where did it come from? Is it contaminated, and with what? You must also be able to prove each answer.
The main reference text comes from the European Medicines Agency (EMA), the European Union’s medicines regulator. EMA’s Committee on Herbal Medicinal Products (HMPC) first issued guideline EMEA/HMPC/246816/2005, which came into effect in August 2006. The HMPC adopted a revised version, EMA/HMPC/246816/2005 Rev. 1, on 9 July 2025. Rev. 1 is now the current version. It adds an annex on indoor cultivation.
The guideline’s central demand is traceability. Each batch of herbal material must be traceable to its source. Every section below follows from that one demand.
What to do: Find the guideline by its code, EMA/HMPC/246816/2005 Rev. 1, on the EMA website and read it before you plan any building. Then you will know which requirements apply to your crop, and you will not spend money on things it does not ask for.
2. Where Farm Practice Ends and Medicine Manufacturing Begins
GACP covers the living plant and the freshly harvested crop. It runs from seed through irrigation, plant protection, harvest and drying, and ends with packed material in storage.
Once the material is turned into a medicine, a different standard takes over: Good Manufacturing Practice (GMP). In Europe, GMP is set out in EudraLex Volume 4, the EU’s collected GMP rules (EU-GMP explained). Part I covers the quality system, personnel, documentation, production, quality control and self-inspection.
Two annexes matter most for cannabis. Annex 7 covers herbal medicines. Annex 16 covers batch certification by a Qualified Person, a named person who is legally responsible for signing off each batch before release.
Most projects split the work like this: growing and first drying under GACP, and extraction under GMP. This split is common industry practice. It is not a clause-by-clause rule taken from Annex 7, so confirm the exact boundary with your buyer.
| Aspect | Cultivation and collection standard (GACP) | Manufacturing standard (GMP) |
|---|---|---|
| Covers | Crop, harvest, drying, packing, storage | Manufacture of the medicine |
| Main text | Guideline EMA/HMPC/246816/2005 Rev. 1 | EudraLex Volume 4 and its annexes |
| Basic unit | A batch traceable to its source | A manufactured batch, certified |
| Release | Buyer accepts the batch against an agreed specification | Batch certification under Annex 16 |
Translator’s note: In Thailand, extraction also needs its own licence. The Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569 came into force on 26 April 2026. It allows extracts above 0.2% THC to be licensed only to three groups: Thai juristic persons that are not “foreign” under the Foreign Business Act B.E. 2542, state agencies, and the Thai Red Cross Society (the 2569 regulations explained). If you plan to extract, check whether you are eligible for a licence before you choose a quality standard.
What to do: On one page, list each step from seed to shipment. Mark which steps your farm does and which steps your buyer or a licensed manufacturer does. This tells you which standard each step must meet.
3. The Records at the Core
If an action is not written down, it did not happen
The guideline requires records of “all processes and procedures that may impact the quality of the product”. GMP adds that records must show “all the steps required by the defined procedures and instructions were in fact taken.”
An auditor who arrives a year later cannot see your crop or your drying room as they were then. All the auditor can see are your records. A gap in a log means there was no control during that period, so the material from that period counts as unproven.
Tracing from the mother plant to the finished lot
Each mother plant (the plant you take cuttings from) gets its own code. Its cuttings take a propagation batch number. At harvest, each growing block becomes a dated lot, meaning one unit of harvested material with one code. Every later step records what went in, what came out, and the yield.
The trace must work in both directions. From a finished lot, you must be able to reach its mother plant and every spray it received. From any spray record, you must be able to reach every lot that could carry residue from that spray.
Law-firm summaries of Thailand’s GACP certification say growers must keep seed-to-sale records. These records cover where the seed came from, fertiliser logs, pest-management reports, harvest dates and quality-control tests.
| Record type | What it must show | Common failure |
|---|---|---|
| Procedures | Approved, with version number and date | Two versions in use at the same time |
| Training | Who was trained, on which version, by whom, when | Training happened but was never recorded |
| Seed and propagation | Identity, origin, mother plant line | Genetics of unclear origin |
| Irrigation and fertiliser | Water source, product, rate, date, test results | Rates written from memory |
| Plant protection | Product, rate, date, days between spraying and harvest | Days to harvest left blank |
| Environmental monitoring | Temperature, humidity and other daily indoor readings | Data collected but never reviewed |
| Harvest and drying | Lot, dates, weights, water activity | Weights that do not add up |
| Deviations and self-inspection | Investigation, correction, owner, closure | Problems never logged, or logged and never closed |
Indoor farms must identify their critical process parameters, meaning the conditions that most affect quality, such as temperature and humidity, and keep them under control. In practice that means recording them daily and having someone review them. The review is the step that fails more often.
Translator’s note: In humid Thai rooms, paper logs get damp, fade and go missing. Keep a bound notebook with numbered pages outside the wet areas, or use a spreadsheet or app that stamps the date and time automatically. Choose temperature and humidity loggers with their own battery, so recording continues through a power cut.
What to do: For the next two weeks, fill in every log on the same day the work is done. At the end of each week, have a second person read the logs and sign them. This shows you which records your team skips before an auditor finds out.
4. Staff, Training and Hygiene
The guideline says staff must “have a high degree of personal hygiene”. Training must be recorded: the person trained, the procedure version taught, the trainer, and the date.
Hygiene protects in two directions. First, you protect the crop from people. Anyone with a known infectious disease that can spread must be kept away from areas where they would touch the material. Second, you protect people from the crop. Staff must be shielded from plant material that is toxic or may cause allergies.
Asking staff to report illness, wearing gloves and wearing hair covers are common industry practice. The guideline does not list them as separate requirements.
Responsibilities must be assigned to named people: the quality system, records, release of lots, and training. At harvest, named supervisors must oversee the workers who collect the crop.
Translator’s note: Many farms in the region hire day workers at harvest. Every person who handles the crop needs a training record, even for one day of work. Give a short briefing in the worker’s own language. Then have each worker sign a sheet that shows the procedure version covered.
What to do: Write one page that puts a name next to each of the four duties: quality system, records, release and training. That way each duty has an owner, and no task falls between two people.
5. Farm Site and Buildings
Medicinal plants “should not be grown in soil or substrate contaminated with sludge, heavy metals, residues”. So you must know how the land was used before. Settle this with a written land-use enquiry and a baseline soil analysis, meaning a soil test done before the first planting.
This matters for cannabis in particular. A 2020 review by Montoya and colleagues in Frontiers in Pharmacology notes that cannabis is a hyperaccumulator. It takes up metals from the soil and stores them in tissues throughout the plant.
Manure “should be thoroughly composted and should be void of human faeces.”
Translator’s note: Much farmland in Thailand and Southeast Asia has a history of rice, cassava, sugarcane or orchards, often with years of chemical inputs. Some plots sit near roads, factories or mines. Ask the previous owner and the neighbours what was grown and sprayed, and keep their answers in writing. If you grow in bought substrate such as coco coir or peat, keep the supplier’s batch number and any analysis they provide.
Water, drainage and keeping clean and dirty flows apart
Irrigation water “should comply with the country of destination’s regional/ national quality standards”. If you sell abroad, the buyer’s country’s water standard may apply instead of the local one.
Buildings used for processing “must be clean”. They “must provide adequate protection… against birds, insects, rodents and domestic animals”. In practice this means:
- sealed rooms and screened openings;
- bait stations outside the product areas;
- drains that never carry water from the washing area into a clean area;
- a layout that keeps wet incoming crop, waste and packed product apart.
Translator’s note: In the rainy season, drains overflow and blocked gutters back up. Check where wash water goes during a heavy storm, not only on a dry day. The quality of well and canal water also changes between seasons, so test it in both the dry and the wet season.
What to do: Draw a plan of your buildings. Use different colours to mark the paths of fresh crop, waste, packed product and wash water. Wherever two paths cross, change the layout or the timing, because crossing points are where clean material gets contaminated.
6. Seeds and Planting Material
The identity of your starting material is the first thing an auditor checks. It is also the first thing many farms cannot prove.
Seeds “should originate from plants that have been accurately identified in terms of genus, species, variety/ cultivar/ chemotype”. A chemotype is the plant’s chemical type, for example THC-dominant or CBD-dominant (chemotypes explained). Seeds must be “free from pests and diseases”. They should also be free of seeds from other species, especially species that contain toxic compounds.
Each mother plant needs its own code and a record of its source, health, treatments and cuttings taken (mother plants explained). A disease or pesticide residue on a mother plant passes into every lot grown from her cuttings.
Translator’s note: Buying clones from other farms is common in Thailand, but it is risky. Clones can bring in pests, hop latent viroid (HLVd, a disease that often shows no symptoms; explained here), or the wrong variety under a familiar name. Keep new plants in a separate quarantine area before they go near your mothers. Ask the seller for written proof of origin. For seed, keep the packet, the invoice, the breeder’s name and any lot number.
What to do: This week, tag every mother plant with a code. Start a one-line record for each cutting session. If a problem shows up later, you can then find the mother plant and every lot affected.
7. Crop Records
The guideline states that “the chosen method of cultivation should be described in a standard operating procedure”. A standard operating procedure (SOP) is a written, step-by-step work instruction. Because the method is written down, any departure from it (a deviation) must also be recorded and justified.
Irrigation and fertiliser logs must be written at the time of the work, not rebuilt later. Each entry shows the block, date, product and its batch number, rate, volume and operator. Keep batch numbers on your nutrient stocks too. If one input turns out to be faulty, you can then trace every crop that received it.
Sensor calibration, meaning checking each sensor against a reference and recording the result, belongs in the environmental records.
Translator’s note: Before you buy a fertiliser, check that it is registered for sale in Thailand (how to verify a fertiliser). Photograph the label of each new batch and file the photo with your log.
Spray records and the days between spraying and harvest
The guideline says: “Pesticide and herbicide applications should be avoided as far as possible.” When a product is used, “the application should be carried out only by qualified staff using approved equipment”. National maximum residue limits must be respected. A maximum residue limit is the highest amount of a pesticide legally allowed to remain on the crop.
Each spray record shows the product, active substance, rate, date, area treated and operator. It must also show the number of days between treatment and harvest. That last field is the one most often left blank.
Translator’s note: In Thailand, use only pesticides registered with the Department of Agriculture (กรมวิชาการเกษตร), and use them only as the label directs (what you may legally spray under Thai GACP).
What to do: Add a “days to harvest” column to your spray form. Do not let anyone file a record with that column empty. Without it, you cannot show that residue risk was managed for that lot.
8. Pest Control Under This Standard
Prevention comes first. Chemical control costs you in chemicals, and it also adds a lot of paperwork.
Preventive methods create few records: keeping pests out, cleaning, resistant genetics, scouting (regular checks for pests) and biological control (integrated pest management explained). Every chemical treatment, by contrast, raises four questions in every market you sell to. What residue is left? What is the legal limit? How many days to harvest? How will you test for it?
So your list of allowed products should be short. The 2020 Montoya review shows why this matters. Citing earlier work by Russo (2016), it reports that 84% of 26 cannabis samples from Washington state (USA) dispensaries contained pesticides, with up to 24 different agents detected.
What to do: Write your restricted product list now. List the few registered products you would use, the pest each one targets, and the days to harvest from each label. Decisions made in advance are better than decisions made during an outbreak.
9. Harvest, Drying, Trimming and First Processing
Harvest the crop “at the best possible quality”, “avoiding wet soil, dew, rain, or exceptionally high air humidity”. Cutting tools “must be appropriately cleaned and adjusted”. Harvested material “should not come into direct contact with the soil or floor”.
For open-air drying, material “must be spread out in a thin layer”. Keep the use of wood-fired and petrol-fired ovens to a minimum. This limits polycyclic aromatic hydrocarbons, harmful compounds produced when fuel burns.
Water activity, moisture and proving your cleaning works
Water activity (written aw) measures how much of the water in dried material is free for moulds and bacteria to use. It runs from 0 to 1. It is not the same as moisture content, which is the total water in the material.
A 2023 review by Gwinn and colleagues in Frontiers in Microbiology reports that water activity below 0.7 “prevents the growth of most fungi”. However, Penicillium and Aspergillus moulds “can survive at aw of 0.62–0.7”. The authors call this range suboptimal for the moulds, not safe. They also report that drying time and final moisture both strongly affect mould levels.
Machine parts “must be cleaned after use to ensure that remaining residue does not result in subsequent cross-contamination”. Many operators also carry out cleaning validation: swab tests or visual checks that prove a cleaning method actually removes residue. This is common industry practice rather than a written guideline requirement.
Drying in a tropical climate
In Southeast Asia, drying is where a GACP operation most often succeeds or fails (drying at very high humidity: Thai setups compared). At 80% outdoor humidity, flower dried in an open shed with a fan is at real risk of mould. Mould toxins (mycotoxins) such as aflatoxins stay in the flower even after the mould dies.
A drying room here should be enclosed and climate-controlled. Temperature and humidity should be recorded throughout every batch. The room must be large enough for your biggest harvest. In this climate it is usually the largest single facility cost of a GACP farm, so design it before anything else.
Translator’s note: Thai conditions add three problems: daytime heat of 30–35 °C, even higher humidity in the rainy season, and power cuts. When the power fails, the dehumidifier and air conditioner stop and room humidity rises. Plan backup power big enough to run them. Record every outage as a deviation, including how long it lasted and what you did with the batch. For outdoor and greenhouse crops, plan harvest days around the rain forecast, because the guideline asks you to avoid harvesting in rain or dew. For sizing, see dehumidifier and air-conditioner sizing for a Thai flowering room.
What to do: Before you build, work out the wet weight of your biggest single harvest and size the drying room for it. Then dry one trial batch in the rainy season. Log temperature and humidity throughout and measure water activity at the end. This shows whether the room can reach below 0.7 before a real crop depends on it.
References for Part 1
- European Medicines Agency, Committee on Herbal Medicinal Products. Guideline on Good Agricultural and Collection Practice for starting materials of herbal origin, EMA/HMPC/246816/2005 Rev. 1 (adopted by the HMPC on 9 July 2025; replaces the first version, in effect from August 2006).
- European Commission. EudraLex Volume 4: Good Manufacturing Practice guidelines, Part I, Annex 7 and Annex 16.
- Montoya and colleagues (2020). Cannabis contaminants limit pharmacological use of cannabidiol. Frontiers in Pharmacology 11:571832 (heavy metal uptake; pesticide findings in Washington state).
- Gwinn and colleagues (2023). Review in Frontiers in Microbiology on microbial and mycotoxin risks in cannabis.
This article is part of the Asiannabis Community educational series on cultivation standards, testing and export. It is general information, not legal or regulatory advice, and is meant for places where growing cannabis is legally permitted.
Continued in Part 2: Good Agricultural and Collection Practice for Cannabis: Storage, Testing, Release, Audits and the Thai Rules (Part 2 of 2)