The plants that made this region famous in the 1970s are largely gone, and most of what circulates about them was written to sell seed rather than to record what was found.
1. How to Read This Article
Landrace history is saturated with folklore, so every claim below carries a marker, and where the record is thin this article says so rather than filling the gap.
| Marker | Meaning |
|---|---|
| documented | traceable to a paper, book, cookbook, notification or news report |
| commonly reported | repeated by growers and collectors, no primary record |
| seedbank claim | from a commercial seed listing, not verifiable |
Cultivation is a criminal matter in Vietnam, Laos and Cambodia, and Thai inflorescence is again tightly controlled. Nothing here is a cultivation guide, nothing explains how to obtain seed, and no vendor is named. Preservation is treated only as work for legal jurisdictions, institutions and licensed operators.
2. What a Landrace Actually Is
A landrace is a locally adapted, farmer-maintained crop population: variable rather than uniform, shaped by one climate and one set of human habits, with no formal breeding records. The standard references are Zeven’s 1998 review in Euphytica and Camacho Villa and colleagues’ 2005 paper in Plant Genetic Resources. Both make the point cannabis writing loses: a landrace is a population, not a strain.
| Landrace | Heirloom | Modern stabilised line | |
|---|---|---|---|
| Maintained | in its region of origin | outside it, by keepers | by a breeder |
| Uniformity | low, wide internal variation | moderate, narrowed away from origin | high, by design |
A Thai population still reseeded in Thailand is a landrace; the same material grown in Europe for fifteen generations is an heirloom of Thai origin. A crossed, selected line sold under a strain name is neither.
Cannabis was domesticated in East Asia in the early Neolithic — documented in Ren and colleagues, Science Advances, 2021, from 110 accessions containing no Southeast Asian material. Halpin-McCormick and colleagues’ 2024 comparison of nine collections identifies none either, so claims that “Thai sativa” forms a distinct clade rest on commercial material of claimed descent.
3. Thailand: The Deepest Written Record in the Region
3.1 Kitchen and traditional pharmacy
Mae Khrua Hua Pa, first printed in 1908 and generally treated as Thailand’s oldest printed cookbook, calls for tender cannabis leaves in an eel curry — documented, and a recipe this ordinary implies an older practice. Beyond it there is testimony, not documentation: leaf in boat noodle broth as a “secret ingredient”, and practitioners at Chao Phraya Abhaibhubejhr Hospital saying publicly that cannabis featured in Thai traditional medicine as far back as Sukhothai.
3.2 The Thai stick was a preparation, not a variety
Every row below is documented in Peter Maguire and Mike Ritter’s Thai Stick (Columbia University Press, 2013).
| Claim | Verdict |
|---|---|
| It was a strain | No — flowers tied to a piece of bamboo, often with hemp thread |
| It was dipped in opium | Maguire calls this an urban myth outright |
| It began as an export product | No — a northeastern kitchen habit traders later found |
| It ran for decades | No — export window roughly 1974 to 1977, ended by oversupply |
| Authentic sticks are still sold | No; products under that name are modern cannabis cigars |
The fame attached to a method of curing and packaging, so “Thai stick genetics” is a category error. Collector writing also splits Thai material into a later, open highland type and a faster lowland type — a seedbank claim, unsurveyed.
3.3 Named Thai selections in the formal record
Four indigenous selections recur in official and press accounts: Hang Kra Rog Phu Phan ST1, Hang Suea Sakonnakhon TT1, Tanao Si Kan Khaw WA1 and Tanao Si Kan Dang RD1. Registration was expected in 2021 per press coverage; no certificate has been seen. A 2024 study by Watanakul and colleagues in the Journal of Pharmacy profiled leaves of the Thai ‘Hang Krarok’ type: over fifty terpenoids led by ocimene, limonene and terpinolene, with caryophyllene prominent. A 2023 paper measured cannabinoids in flowers claimed to be Hang Kra Rog Phu Phan — that phrasing in a title is the lesson.
3.4 What the changes from 2022 to 2026 mean for local genetics
| Date | Change | Effect |
|---|---|---|
| Cannabis Act B.E. 2477 (1935), then Narcotics Act B.E. 2522 (1979) | criminalisation | seed keeping hidden; late-1970s eradication removed standing plants |
| June 2022 | inflorescence delisted, household registration opened | the one open window in fifty years, and the moment imported seed arrived at scale |
| 26 June 2025 | Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568 | prescription-only on the PT 33 form; flower only from sites under Good Agricultural and Collection Practice |
2022 was the best moment in half a century to survey surviving Thai populations; the energy went into imported cultivars instead.
4. Laos: Fibre, Seed and Cloth
Laos is the region’s clearest case of cannabis as a fibre and seed crop rather than a drug crop, documented through textile research among Hmong communities. Clarke and Gu’s 1998 paper in the Journal of the International Hemp Association records hemp interplanted with maize, fields rotated after two years, a long process of retting, beating and spinning before weaving, and Hmong women carrying hemp seed when they moved settlement. But it covered Yunnan and northern Vietnam, not Laos, so extending it southward is inference.
Cultivation is illegal in Laos and penalties are severe, with reference sources noting a mandatory death penalty for certain drug offences from 2009. Traditional Lao growing regions appear only in tourist and collector writing, and the “happy” menu trade in Vang Vieng is a modern commercial phenomenon.
5. Vietnam: A Thin Record and One Very Loud Claim
Cannabis is prohibited in Vietnam, where it is called cần sa.
| Item | Status |
|---|---|
| Arrival around the sixteenth century, used in food and medicine | commonly reported, no primary source |
| Hemp and fibre use by Hmong communities in Lào Cai, Lai Châu and Yên Bái | documented — Clarke and Gu, 1998 |
| Eradication from 1969 by the United States aid mission, with aerial spraying in the Mekong Delta | documented |
No collection report, herbarium survey or chemical study of any Vietnamese population exists.
5.1 The Đà Lạt question
Đà Lạt sativa is the region’s most repeated landrace claim, and tracing it leads to commercial listings and forum threads rather than a collection record. One principal listing calls the material more a rescue of an old seed lot than a preservation, gives Đà Lạt only as a geographic tag, and provides no named collector, no year, no village or altitude, and no flowering-time data. It may be genuine, but there is nothing to check, and no documented Đà Lạt population appears in the literature. An article stating its flowering time or aroma with confidence describes a product, not a place.
6. Cambodia: Kitchen Herb and Tourist Attraction
| Claim | Status |
|---|---|
| Traditionally grown, used in food and medicine | documented, without recipe or region detail |
| It appears in named traditional Khmer soups | commonly reported; no cookbook or ethnographic record found |
| Illegal from 1961 under the Single Convention, again in 1992; enforcement intermittent | documented |
| Tourist “happy” pizza existed by the mid-2000s | documented — New York Times, April 2006, Sihanoukville |
| “Happy” restaurants continue Khmer tradition | not documented — a tourist-economy phenomenon of the last two decades |
The real loss is quiet: a household herb tradition never written down, in a country whose documentary record suffered catastrophically in the 1970s.
7. Traits of Southeast Asian Sativa Populations
Everything below is what these populations are reported to do; almost none has been measured on documented in-situ plants.
7.1 Flowering duration and photoperiod
Near the equator daylength barely changes, so a plant that waits for short days waits a long time. Documented, in Zhang and colleagues’ 2021 study in Frontiers in Plant Science: critical photoperiods across cannabis run from roughly 13 hours 45 minutes to beyond 15 hours 30 minutes, southern material flowered markedly later than northern, and fifteen minutes of daylength changed initiation in sensitive types. Fourteen to twenty weeks of flowering is commonly reported here, on grower figures rather than measurement.
7.2 Structure, stretch and flower density
Commonly reported across independent accounts: extreme internode extension after the switch to flowering, a tall open frame, low flower density in long airy clusters, thin leaflets, and late uneven ripening on one plant.
7.3 Humidity and mould
Monsoon conditions mean months of high humidity during flowering, exactly when Botrytis cinerea — grey mould, bud rot — does its damage. Pathology work on greenhouse cannabis, notably from Punja’s group, identifies high humidity and dense inflorescence structure as the principal drivers: a loose airy flower dries after rain, a dense one holds water. Regional mould tolerance is therefore plausible, but genetic resistance in named populations is commonly reported only, and structural escape is a different trait.
7.4 Aroma chemistry
That Thai leaf profile — ocimene, limonene and terpinolene dominant, caryophyllene present — is unlike the myrcene-led profiles typical of commercial cultivars. But it is one data point on leaf from one Thai type, not a regional fingerprint; linalool, pinene and humulene appear in regional descriptions with no published quantification.
7.5 Why these plants struggle at northern latitudes
Long summer days delay or prevent flowering; autumn arrives before ripeness, so frost and rain land mid-flower; a sixteen-week flowering period does not fit a short frost-free season; the stretch exceeds most indoor rooms; and cool humid nights mean slow ripening in the conditions that most favour mould. This is not fragility, it is fit: a plant tuned to a twelve-hour year and a monsoon is behaving correctly when it refuses to finish in Poland in October.
8. Why These Genetics Matter to Modern Breeding
| Trait carried | Why it is scarce elsewhere | Who needs it |
|---|---|---|
| Tolerance of near-constant twelve-hour days | temperate breeding never had to select for it | licensed tropical cultivation |
| Escape from wet-season bud rot | dense-flowered cultivars were bred under dehumidifiers | humid greenhouse and outdoor crops |
| Terpinolene- and ocimene-led aroma | the pool narrowed to myrcene and limonene | breeding off the standard profile |
Cannabis is dioecious and wind-pollinated, so a landrace hybridises with anything flowering nearby, and no certification system or variety register protects it. One season of stray pollen is enough.
9. Genetic Erosion: How a Landrace Disappears
The dominant mechanism is dilution, not eradication. Once imported photoperiod-fast, dense-flowered cultivars — descendants of OG Kush, Blue Dream, Girl Scout Cookies and Gorilla Glue — grow in a village, their pollen reaches whatever flowers nearby. The hybrids finish sooner and yield denser flower, so those are the seeds growers keep, and within a few cycles the local population is a hybrid swarm. The second mechanism is the end of seed saving: growing becomes criminal, younger generations leave farming, bought seed is cheaper, and oral knowledge dies with its holders.
Halpin-McCormick and colleagues in 2024 found broader genetic diversity in modern cultivars than in the landrace accessions available to them, which says as much about how few landraces sit in collections as about the plants. Welling and colleagues in Frontiers in Plant Science in 2016 named the cause: narcotics conventions have constrained cannabis genetic resource collections, leaving East Asian material a priority yet poorly represented. Prohibition suppressed not only cultivation but the archiving.
10. What Preservation Actually Requires
The framework is the same as for any outcrossing crop, set out in the Food and Agriculture Organization’s Genebank Standards for Plant Genetic Resources.
Isolated seed increase. Cannabis is wind-pollinated and dioecious, so an increase that is not isolated is a cross; isolation means distance, enclosed structures, or pollination of bagged branches.
Adequate population size. A landrace’s value is its internal variation, so increase from two or three plants gives a bottlenecked line that no longer represents the source. Standards require a population adequate to maintain genetic integrity but set no number for cannabis; a precise figure quoted as official is improvised.
Documentation of origin. Locality with coordinates where possible, altitude, date, collector, local name and use, number of parent plants, generations since collection. Every one is missing from the Đà Lạt material.
Lawfully this work belongs to regional research institutes and universities, which alone can sample in the field; to licensed cultivators where cultivation is legal; to public genebanks; and to herbaria holding lawfully collected specimens. Community members can contribute oral history and photographs, nothing involving seed. Informal cross-border seed movement is not on that list: it is a crime in most of the region and destroys provenance anyway.
10.1 Ethics and the legal reality
- The origin community holds the knowledge and the material; benefit-sharing obligations under national law and the Convention on Biological Diversity are not optional.
- A local name is not a brand: attaching a place name to a product with no collection record is misrepresentation, and it is this subject’s largest source of pollution.
- Collect from many plants, record how many, and never ask anyone to break their own country’s law on your behalf.
| Country | Cultivation | Seed movement |
|---|---|---|
| Thailand | licensed only; inflorescence prescription-controlled since June 2025 | licensing and plant import rules apply |
| Laos | illegal, severe drug penalties | criminal matter |
| Vietnam | illegal | criminal matter |
| Cambodia | illegal since the 1990s, enforcement intermittent | criminal matter |
Tolerated is not legal: an unenforced law is still a law, and priorities change without notice. Carrying cannabis seed across a border here is a drug offence regardless of intent, and preservation framing is no defence.
Now the part that is genuinely yours. If your family grew cannabis for fibre, for the cooking pot, or for a grandmother’s remedy — in Isan, in the northern Thai hills, in Lào Cai or Lai Châu, in the Lao uplands, in a Khmer village — that is primary evidence, and very little of it has ever been written down. Tell us the local name and what it means, what it was used for and which part, how tall it grew, how long it took, and who kept the seed. If you have old photographs, or plants growing near you today, post them with a rough location and a date. Corrections are especially welcome: if something above is wrong, say how you know.
This article is part of the Asiannabis Community educational series on cannabis genetics and heritage. Content is for educational purposes within jurisdictions where cannabis cultivation is legally permitted.