Growing and Harvesting Kratom in a Tropical Climate: Thai Varieties, Soil, Drying, Storage and Research Gaps (Part 2 of 2)

Kratom_4U · October 21, 2026, 4:40pm

Kratom (Mitragyna speciosa) is a tropical tree in the coffee family, native to southern Thailand and nearby countries. This part covers what is known, and not known, about Thai kratom types, soil and feeding, harvest, drying and storage. It also lists the research questions Thai growers could answer themselves. It separates results from controlled studies from common practice that has no published support.

Where this applies (status as of October 2026). Kratom is illegal or controlled in Malaysia, Singapore, Vietnam and Myanmar, and restricted in several other countries. This guide is only for places where growing kratom is legal. In Thailand, the Kratom Plant Act B.E. 2565 (2022) has been in force since 27 August 2022, and growing for personal use needs no licence. For details, read Kratom Law in Thailand After 2021, and Across the Region.

This guide is about growing the tree, not about using it. Nothing here encourages you to consume kratom.

This is Part 2. Part 1: Growing and Harvesting Kratom in a Tropical Climate

Thai varieties: no comparison data yet

Thai growers and traders name local types by the look of the leaf and its veins:

ก้านแดง (Kan Daeng): red-vein
ก้านเขียว (Kan Khiao): green-vein
หางกั้ง (Hang Kang, literally “mantis-shrimp tail”): named for its jagged leaf tip

The cultivars in the 2025 US propagation study (see Part 1) were US trade names. A search for this article found no published controlled data comparing Thai types on rooting, growth or alkaloid profile. Claims that one Thai type is “stronger” or “easier” come from traditional knowledge, not measurements. This is one of the clearest research gaps listed at the end of this part.

Translator’s note: A name based on leaf appearance does not prove which genetic line a plant comes from. When you buy plants or cuttings, see the mother tree if possible. Tag each tree with its type name, where it came from and its planting date. These records let you compare types on your own land later.

Soil, water and nutrition: what could not be verified

The published record on this topic is very thin. No controlled studies could be found on kratom’s best soil pH (acidity), nutrient needs, response to fertiliser, watering schedule or plant spacing.

A Thai study (Chongdi and colleagues, International Journal of Plant Biology, 2025) compared kratom growth and leaf traits in the south, centre and northeast of Thailand. Leaf traits here means measurable features such as leaf thickness and chlorophyll content. Leaf thickness and chlorophyll content did not differ between regions. Trees in the northeast had lower photosynthetic efficiency. The study does not give a fertiliser programme.

For that reason, this guide gives no nutrient schedule. An N-P-K table for kratom would look precise, but it would be invented. Following an invented table can cost you a whole season.

Some points can be inferred from the plant’s natural habitat, though not from a trial:

Kratom is native to moist lowlands that often flood for part of the year. So it is probably not drought-tolerant. It probably copes with waterlogged roots better than most trees.
As an understorey tree in the coffee family, it probably prefers acidic soil rich in organic matter, roughly the same range as coffee.
It is a perennial that loses a lot of leaf to harvest every year. So it will need regular feeding over the years, not one feed at planting.

Treat all three as reasoning from the plant’s habitat, not as measurements. If you plant at scale, a soil test and a small trial block will tell you more than anything published.

Translator’s note: In Thailand, ask your local Land Development Department (กรมพัฒนาที่ดิน) station about soil testing. If kratom is not drought-tolerant, plan irrigation for the dry season, especially in areas with long dry months such as the Northeast. Use only fertilisers that are legally registered in Thailand. The forum topic Verifying a Fertiliser Is Legally in Thailand explains how to check. For a simple trial, split one block into two or three feeding levels. Record leaf yield per tree at every harvest to see which level pays.

Harvest and drying: where the leaf chemistry is decided

Growers often underestimate this step. The reason is a finding explained in more detail in Kratom: Botany, Alkaloids, and How It Actually Works.

A 2022 study in PLOS One tested young kratom plants under three light levels in Florida (see Part 1). It used a team led by Zhang M. at the University of Florida. 7-hydroxymitragynine (7-OH), a minor alkaloid, could not be detected in living leaf under any treatment. The researchers concluded that 7-OH forms after harvest. They believe it forms through oxidation of mitragynine, a chemical reaction with oxygen in the air.

If they are right, drying does more than keep or spoil the leaf. It may partly decide the leaf’s chemical makeup. Temperature, drying time, exposure to air and light during drying probably affect how much mitragynine turns into 7-OH. Two batches from the same trees, dried differently, can end up chemically different.

What this means for processed products

This also matters if you make processed products. Thai FDA rules for food supplements and herbal products containing kratom set daily limits for mitragynine. Thai news reports show these limits have changed more than once since 2024. According to the law firm Tilleke & Gibbins (2024), adding 7-OH to food supplements is not allowed. Check the current rules in the Kratom Law post.

Either way, the practical step is the same. Send each finished lot to a lab for testing. Do not assume its alkaloid content.

Drying method: traditional practice and an experiment worth running

No controlled data could be found on the best drying temperature or time for alkaloid content. In southern Thailand, the traditional method is drying whole leaves in the shade. This fits with keeping heat and light low. With no data available, the traditional method is a reasonable default.

For anyone producing at scale, this is the most valuable experiment available, and almost nobody has run it. Split one harvest into equal portions and dry each a different way. Have a lab test every portion. You will then know something the published research does not.

Translator’s note: In the Thai rainy season, outdoor humidity often sits at 85–95%. Shade-drying then becomes slow, and leaves can go mouldy. Mouldy leaf is both a quality and a safety problem. Dry in thin layers on racks, under a roof, with fans moving air. Use a room with a dehumidifier if you have one. The forum topic Drying Cannabis at 85–95% Ambient Humidity covers the same problem for cannabis. For alkaloid testing, ask other growers in the forum’s B2B Services section which Thai labs they use. For a first trial, split one harvest into two portions, such as a shade rack and a fan room. Record temperature and drying hours for each, then test both.

Leaf age at harvest

The PLOS One study ran from September to December 2018. It did not test whether leaf age changes alkaloid content. No other controlled data could be found. Common practice is to pick mature leaves and leave young growth on the tree. That makes sense for tree health either way. Note which leaves you pick at each harvest, so later lab results can be linked to leaf age.

Storage

If 7-OH forms by oxidation, storage carries on the chemistry that drying started. The obvious approach is to store leaf cool, dark, dry and sealed against air. No data could be found on how much this matters. Put a date on every lot.

Translator’s note: In a Thai room, dried leaf can quickly take up moisture from the air again. Use airtight containers with food-grade desiccant packs, and keep them out of sunlight. Label each container with harvest date, drying method and source tree or type. If a lot tests differently later, the label shows you what changed.

Open research questions

Thailand has a legal framework for growing kratom and suitable growing conditions. It also has farmers with generations of experience and universities able to do the research. The open questions are simple ones:

How Thai types (ก้านแดง, ก้านเขียว, หางกั้ง) compare in alkaloid profile and rooting under standard conditions
How the drying method affects final alkaloid content
How leaf age at harvest affects alkaloid content
How kratom responds to fertiliser, and which soil conditions suit it best
What shade level works best for mature trees in Thai fields, beyond the three light levels already tested

Answering any one of these would add new knowledge. A grower who runs a careful trial with lab analysis is doing work no one has published yet. If you run such a trial, post your method and results below this topic so other growers can compare.

Sources: Zhang M, Sharma A, León F, Avery B, Kjelgren R, McCurdy CR, Pearson BJ. “Plant growth and phytoactive alkaloid synthesis in kratom [Mitragyna speciosa (Korth.)] in response to varying radiance.” PLOS One 2022;17(4):e0259326. doi:10.1371/journal.pone.0259326; Zhang M, Montanez C, Pearson BJ, Li Y, Chen J. “Aeroponics enables consistent cutting propagation of kratom (Mitragyna speciosa): impacts of photoperiod, cultivar, and rooting hormone.” Frontiers in Plant Science 2025;16. doi:10.3389/fpls.2025.1650327 (the correction doi:10.3389/fpls.2025.1697035 changes figures only); Kratom Plant Act B.E. 2565 (2022), published in the Royal Thai Government Gazette 26 August 2022, in force 27 August 2022; Tilleke & Gibbins, “Thailand’s New Legal Framework for Kratom” (2022) and “Thailand’s Updated Guidelines on Kratom in Food and Herbal Products” (2024).