Sooner or later, almost every conversation about growing in a small tent arrives at the same question: "Am I actually allowed to do this?" It usually comes with a reason attached. "I've got a prescription now." "It's one plant in a cupboard, not a farm." "The seeds were sold legally." "Hemp is legal, isn't it?" Each of these sounds reasonable, and each is repeated often enough on forums to feel like settled fact.

Elsewhere in this series we put grower practice next to research. Here the frame changes: common assumptions on one side, the official documents on the other. We use two Home Office factsheets, one on cannabis, CBD and other cannabinoids (updated 3 October 2024) and one on industrial hemp licensing (updated 18 December 2025). We also use the European Medicines Agency's 2006 guideline on Good Agricultural and Collection Practice, usually shortened to GACP, which describes how medicinal plants should be grown and handled when quality matters.

Before anything else: this is not legal advice. Both factsheets say the same about themselves: the drugs licensing factsheet is "general guidance only" and "not legal advice", and anyone in doubt should "seek their own independent legal advice" (Home Office, 2024, para. 2). CannaTinker is an educational project. Nothing here explains how to avoid the law or should be read as permission to grow.

What kind of documents these are

A factsheet is not an Act of Parliament. It is the department's summary of how it reads the law and runs its licensing system. The legislation itself is the Misuse of Drugs Act 1971 and the regulations made under it, chiefly the Misuse of Drugs Regulations 2001. Guidance can be revised: the hemp factsheet gives its THC limit as the figure that applies "at the time of drafting" (Home Office, 2025).

The Home Office considers licence applications "in England, Wales and Scotland" (Home Office, 2024, para. 9); Northern Ireland is not covered by these documents, or by this article. And the factsheets cover drugs law only, not "other (non-drugs) regimes such as medicines or foods" (para. 2), which may also apply to a product such as a CBD oil.

The starting point: Class B and the 1971 Act

Cannabis is a Class B controlled drug under the Misuse of Drugs Act 1971. The Act defines cannabis, "in essence", as "the plant or any part of the plant", with three exceptions: the mature stalk, fibre produced from the mature stalk, and the seed (Home Office, 2024, para. 3).

It is therefore unlawful to possess, supply, offer to supply, produce, import or export cannabis except under a Home Office licence. Separately, "it is also an offence to cultivate any plant of the genus Cannabis except under a Home Office licence" (Home Office, 2024, para. 3). The hemp factsheet repeats the same sentence word for word (Home Office, 2025).

The chemistry is controlled as well as the plant. The factsheet lists cannabinol (CBN) and "cannabinol derivatives", a legal category that includes delta-9-tetrahydrocannabinol, or THC, as Class B drugs in their own right (Home Office, 2024, para. 4). Growers who know their cannabinoids will notice that CBN, which some associate with older flowers, appears here by name.

Assumption: "A few plants in a tent are too small to matter"

The documents give this no support. The cultivation offence in the factsheet applies to "any plant of the genus Cannabis". Neither factsheet mentions a number of plants, a tent size, a floor area or a personal-use allowance below which the rule stops applying. Paragraph 14 restates it plainly: "It is unlawful to cultivate or possess cannabis plants ... without the requisite Home Office licence" (Home Office, 2024, para. 14).

Licensing is a regulatory process, not a plant count. The Home Office considers each application "carefully on its merits", including "the ability of the applicant to comply with regulatory standards" (Home Office, 2024, para. 9), and may weigh the views of other regulators such as the Medicines and Healthcare products Regulatory Agency (para. 10). There are "two separate licensing regimes relating to cannabis cultivation" (para. 14): one for low-THC industrial hemp, described below, and one for everything else.

This one contains a grain of truth. Seeds really are excluded from the legal definition of cannabis (Home Office, 2024, para. 3). But the cultivation offence is about the plant, not the seed. Once a seed germinates, there is a plant of the genus Cannabis, and the legality of the seed in the packet does not carry over to the plant in the pot.

Assumption: "A prescription lets me grow my own"

Since 2018 the UK has had a legal route to medical cannabis, and it is easy to see why people assume it extends to home growing. "Cannabis-based products for medicinal use in humans", abbreviated to CBPMs, are defined in the 2001 Regulations. In plain terms, they are preparations or products that are or contain cannabis, cannabis resin, cannabinol or a cannabinol derivative, are produced for medicinal use in humans, and are medicinal products or ingredients of one (Home Office, 2024, paras 7 and 15). In 2018 CBPMs were placed in Schedule 2 of the Regulations. They remain Class B drugs, with additional controls set out in Regulation 16A (Home Office, 2024, para. 7). Two licensed medicines, Sativex and Epidyolex, are scheduled separately (para. 8).

Who may do what? The factsheet explains that "specialist medical practitioners can prescribe CBPMs without requiring a Home Office licence". Companies that possess, supply, produce, manufacture, import or export these products need Home Office licences, and a limited exemption lets pharmacists acting in their professional capacity handle them (Home Office, 2024, para. 17).

That is the whole chain the factsheet describes: a specialist prescribes, a licensed supply chain produces the product, and a pharmacist dispenses it. The patient receives a product. Nowhere does the factsheet give an exception that lets a patient cultivate the plant. The plain summary runs through this whole series: in the UK, growing cannabis, even with a prescription, requires a Home Office licence. A prescription is permission to be supplied with a specific medicine. It is not permission to produce it.

Hemp may be grown in the UK, but only under licence and only for particular purposes. Licences "may be issued for the cultivation of cannabis plants with a low tetrahydrocannabinol (THC) content for the production of hemp fibre for industrial purposes or the obtaining of seeds which are then pressed for their oil" (Home Office, 2025). Only the non-controlled parts may be used, "seeds and fibre/ mature stalk", and the factsheet is explicit that the policy "does not allow for use of 'green' material- i.e. the leaves and flowers as these are controlled parts of the plant". After harvest, the controlled parts have to be retted at the licensed location (the controlled rotting used to free the fibres) or otherwise lawfully disposed of.

Applications that seek "to produce so-called CBD oils from controlled parts of the plant" will not be considered under the hemp licensing provision, "irrespective of what 'variety' of cannabis is intended to be cultivated". A low-THC variety does not turn its flowers into a legal product.

The often-quoted THC figure needs care. Licences cover only "approved seed types" with THC not above the percentage in the Misuse of Drugs (Fees) Regulations 2010, which "at the time of drafting is 0.2%". The factsheet stresses that this number is used "solely to identify varieties which may potentially be cultivated" and to set the fee level. It is a filter for which seed may be sown, not a legal threshold that makes any plant under 0.2% THC uncontrolled.

The practical requirements show what a licensed hemp grow looks like:

  • Each grower and each site must be licensed individually, and the licence covers both cultivation and possession.
  • Every applicant must pass an enhanced DBS (criminal records) check.
  • There must be a defined commercial end use, backed by record-keeping documents and seed invoices.
  • Licence holders "should inform your local police of your growing locations".
  • A new low-THC licence costs £580, a renewal £326, and a compliance visit, if needed, £1,371. A licence to grow high-THC cannabis, or to use the controlled parts of so-called hemp varieties, costs £4,700.
  • Growers "should not sow until they hold a licence".

(All from Home Office, 2025.) This is farming under a light-touch but real regulatory regime, and it has nothing to do with flowers in a tent.

Pure CBD, "as an isolated substance, in its pure form", is not controlled under the 1971 Act (Home Office, 2024, para. 20). The difficulty is that CBD products are rarely pure. The Home Office view is that "it is nearly impossible to extract and isolate CBD from the cannabis plant or to create CBD synthetically without traces of other controlled cannabinoids, such as THC and THC-V" (Home Office, 2024, para. 22). A product containing a controlled cannabinoid is itself controlled. Unless it is a CBPM or a separately scheduled medicine, it is a Class B, Schedule 1 drug (para. 23).

What lets most retail CBD exist is the "exempt product" definition in Regulation 2 of the 2001 Regulations. A product that meets it is not subject to the prohibitions on import, export, production, supply and possession (Home Office, 2024, para. 26). It has three limbs, and the factsheet stresses that "all three limbs of the definition must be met" (para. 28):

  1. The product "is not designed for administration of the controlled drug to a human being or animal".
  2. The controlled drug is packaged or combined in such a way that "it cannot be recovered by readily applicable means or in a yield which constitutes a risk to health".
  3. "No one component part" of the product contains more than one milligram of the controlled drug.

Two details matter more than people expect. The limit applies to the container, "such as a bottle of oil", and "not ... the supposed typical dose" (Home Office, 2024, para. 33). It applies to each controlled cannabinoid separately, and the Home Office expects producers to be able to show compliant levels of delta-9-THC, delta-8-THC and CBN (para. 34). Showing this requires "a full spectrum analysis" by a laboratory accredited to ISO/IEC 17025 (para. 32).

Whether a given product is exempt "will be a matter of fact, determined on a case-by-case basis" (Home Office, 2024, para. 29). The Home Office does not assess such claims for the public (para. 11), and its licensing unit "is not an enforcement agency" (para. 35). Even when the end product is exempt, the grow behind it is not: producing exempt products still requires a licence if the process involves cultivating the plant, "including hemp", or handling its controlled parts (para. 36). And rules abroad "do not override UK legislative requirements" (para. 12).

Assumption: "THCA flower isn't THC, so it isn't controlled"

The factsheet addresses this newer claim directly. THCA, which the factsheet calls THC-A, is the acid form of THC that the living plant actually makes. As a pure, isolated substance, the factsheet says, THC-A "would not be controlled". But it adds that "THC-A readily degrades both naturally, and with a catalyst or environmental change (e.g. heat) to THC", which is controlled (Home Office, 2024, para. 19). (That chemistry is the subject of our post-harvest article.) There is also a simpler point: a flower is part of the plant, and the plant is controlled as cannabis whatever the label says about its chemistry.

What GACP is

The European Medicines Agency's Guideline on Good Agricultural and Collection Practice (GACP) for starting materials of herbal origin was adopted by the agency's Committee on Herbal Medicinal Products in January 2006 and came into effect on 1 August 2006 (EMA/HMPC, 2006). It applies to any plant used to make herbal medicines. It does not mention cannabis by name.

Its purpose is to "ensure appropriate and consistent quality" of medicinal plants, and its reasoning explains why a grow can matter as much as a factory. For herbal preparations, the guideline says, the growing and primary processing of the plant "has a direct influence on the quality" of the active ingredient. Because plants are complex and analytical methods have limits, reproducible quality "requires an adequate quality assurance system for the collection and/or cultivation, harvest and primary processing" (EMA/HMPC, 2006, section 1). In other words, the guideline does not rely on testing the finished product alone.

The guideline's main aim is "to ensure consumer safety". It singles out two things: that plants are "produced hygienically, in order to reduce microbiological load to a minimum", and that they are handled with care at every stage (section 2.2).

Documentation

"All processes and procedures that could affect the quality of the product must be documented" (section 7.1). That includes extreme weather and pests (7.2), the location and history of the field (7.3), and the type, quantity and date of harvest with every fertiliser, pesticide and growth promoter used (7.4). Audit reports are kept for at least ten years (7.10).

Traceability

"Batches of medicinal plant materials should be unambiguously and unmistakeably traceable to their sources", with labelling and batch numbers assigned "as early as possible" (section 7.7). Seeds should come from plants identified by genus, species, "variety/cultivar/chemotype" and origin, and should themselves be traceable (8.1).

Hygiene, harvest and drying

Staff need training and a "high degree of personal hygiene" (section 4.1), and buildings must be clean and protected from pests (5.1–5.2). Plants should be harvested "when they are at the best possible quality", avoiding "wet soil, dew, rain or exceptionally high air humidity" (11.1, 11.3). For open-air drying, the material "must be spread out in a thin layer", raised off the ground, and "attempts must be made to achieve uniform drying ... and thus avoid mould formation" (12.3). For other drying methods, conditions such as temperature, duration and air circulation must suit the plant part and the nature of its active constituents, "such as essential oils", and "must be recorded in detail" (12.4). Dried material should be stored somewhere dry and well aerated, with limited daily temperature swings (14.1).

Why "a standard, not a manual"

The guideline gives no light levels, no feeding schedule and no drying temperature for any particular plant. It tells a producer what must be controlled, recorded and traceable, and leaves the method to them. That is what a quality standard does, and it is why GACP is neither a home-grow guide nor any kind of permission.

One caveat about our copy. The PDF in CannaTinker's collection carries a "Superseded" watermark, so a later revision of the guideline exists. The principles quoted here are the 2006 text, and the factsheets in our collection do not say which version, or which quality standard, UK licensees are expected to meet.

Why GACP matters for medicine quality

A patient needs a prescribed product to be the same from batch to batch and free of contamination. Two studies in CannaTinker's library show how much is at stake.

Danziger and Bernstein (2021) studied a high-CBD medical cultivar, 'Topaz', grown at about one plant per square metre in a naturally lit commercial greenhouse in Israel, to a height of roughly 2.5 m. The lowest flowers on the plant, where light barely reached, had cannabinoid concentrations reduced "by up to 40%" compared with flowers higher up. Contrary to a common industry belief, the main top flower was not always the most potent. Without batch control and testing, a "dose" is not a fixed quantity.

Birenboim et al. (2024) dried small samples of two Israeli medical chemovars, a high-THC type ('240') and a hybrid ('Gen12'), in two ways: in laboratory controlled-atmosphere chambers, or in open air at 15 °C and 50–55% relative humidity. After open-air drying, about 80% of the high-THC flowers were "highly infested" with the mould Alternaria alternata, with some Botrytis cinerea, by day 12. Their main cannabinoid, THCA, fell from 9.5 to 7.6% of dry weight. In the hybrid, both moulds stayed below the detection limit, and its THCA and CBDA held steady. One post-harvest step changed both safety and chemistry, differently in two chemovars: exactly the variation GACP's drying and documentation rules are meant to catch.

Neither study tests GACP itself; they measured cannabinoids and mould at commercial and laboratory scale. They show why a medicines regulator would want growing and drying controlled and written down rather than left to habit.

What this means for a 1×1 tent

For a reader in England, Wales or Scotland the conclusions are about understanding, not technique.

  • Size does not change the rule. The cultivation offence applies to any plant of the genus Cannabis grown without a Home Office licence.
  • A prescription is not a growing licence. The route the factsheet describes for patients is a prescription from a specialist doctor, dispensed by a pharmacist from a licensed supply chain.
  • Hemp and CBD rules do not cover flowers. Hemp licences cover fibre and seed only; leaves and flowers remain controlled. CBD products depend on the exempt-product conditions.
  • When buying CBD, the factsheet's own criteria are a useful guide to what good evidence looks like: a full-spectrum test from an ISO/IEC 17025-accredited laboratory, reported for the whole container.
  • GACP is a way of thinking about quality: records, traceability, hygiene and controlled drying. It is not a manual and grants no permissions.
  • CannaTinker is educational. This series explains the plant; it is not a set of instructions. For your own circumstances, ask a solicitor.

What we know, and what we don't

What the documents say clearly. Cannabis is a Class B drug under the Misuse of Drugs Act 1971. Cultivating any cannabis plant without a Home Office licence is an offence. Seeds are excluded from the definition, but growing one is cultivation. CBPMs have been in Schedule 2 since 2018 and may be prescribed by specialists, but the factsheet sets out no cultivation exception for patients. Hemp licences cover approved low-THC seed for fibre and seed only; leaves and flowers stay controlled. Pure CBD is not controlled, but most CBD products contain controlled cannabinoids and are lawful only if they meet all three limbs of the exempt-product definition. GACP is a quality standard for producers of medicinal plants, built on documentation, traceability and hygiene.

What they do not cover. Neither factsheet discusses penalties, sentencing or how the law is enforced in practice, and this article does not either. They cover England, Wales and Scotland, not Northern Ireland. They exclude medicines, food and other non-drugs regimes. They are guidance, not the legislation, and they can change: the hemp factsheet gives its 0.2% figure as the one that applies "at the time of drafting". Whether any particular CBD product is exempt is decided case by case, and the Home Office does not give that assessment to the public. The GACP copy in our collection is marked as superseded, and our documents do not say which quality standard UK licence holders must follow. Everything here reflects the documents as we hold them, and it is not legal advice.

Sources

Birenboim, M., Brikenstein, N., Duanis-Assaf, D., Maurer, D., Chalupowicz, D., Kenigsbuch, D. and Shimshoni, J.A. (2024) 'In pursuit of optimal quality: cultivar-specific drying approaches for medicinal cannabis', Plants, 13(7), 1049. doi:10.3390/plants13071049.

Danziger, N. and Bernstein, N. (2021) 'Shape matters: plant architecture affects chemical uniformity in large-size medical cannabis plants', Plants, 10(9), 1834. doi:10.3390/plants10091834.

EMA/HMPC (European Medicines Agency, Committee on Herbal Medicinal Products) (2006) Guideline on Good Agricultural and Collection Practice (GACP) for starting materials of herbal origin. EMEA/HMPC/246816/2005. London: EMEA. Available at: https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-good-agricultural-and-collection-practice-gacp-starting-materials-herbal-origin_en.pdf.

Home Office (2024) Drug licensing factsheet: cannabis, CBD and other cannabinoids. Updated 3 October 2024. London: Home Office. Available at: https://www.gov.uk/government/publications/cannabis-cbd-and-other-cannabinoids-drug-licensing-factsheet/drug-licensing-factsheet-cannabis-cbd-and-other-cannabinoids.

Home Office (2025) Industrial hemp licensing factsheet. Updated 18 December 2025. London: Home Office. Available at: https://www.gov.uk/government/publications/industrial-hemp-licensing-guidance/industrial-hemp-licensing-factsheet.