How kratom is processed: from leaf to the bag on your doorstep

Every bag of kratom powder in Canada started as fresh leaves on a tree in Indonesian Borneo and passed through six or seven hands before it was repacked by a Canadian vendor. Understanding those steps explains most of what a lab test can find: where salmonella gets in, why heavy metals show up, why “red” and “green” are mostly about drying, and why the batch number on your bag matters. This is a description of the supply chain, not a how-to.

Last reviewed: November 9, 2026. Part of the KratomSource knowledge base.

1. Harvest

Leaves are picked by hand from cultivated or semi-wild trees, often along the Kapuas River in West Kalimantan, where smallholders can harvest the same trees every few weeks year-round. Pickers take mature leaves; very young leaves are low in alkaloids and the oldest leaves are tough and discoloured. The leaf is a living plant product at this point: wet, warm and carrying whatever bacteria were on the tree, the picker’s hands and the collection sacks. Nothing about a kratom leaf is sterile, which is why microbiological testing of the finished powder is not optional.

2. De-stemming and de-veining

Workers strip the central vein and stem from each leaf, usually by hand. Stems and veins contain less alkaloid and more fibre, so removing them raises the alkaloid concentration of the final powder and improves its texture. Powder sold as “stem and vein” is the by-product. This step is labour-intensive and is one of the reasons processed kratom costs more than the raw leaf price suggests.

3. Drying, and where the colours come from

Drying is the step that creates most of the product variety on a vendor’s menu. Leaves are dried indoors, outdoors in sun, in shade, or in some combination, for hours to days. The vein of a fresh leaf can be reddish or greenish, but the “red”, “green” and “white” categories buyers see are dominated by processing: longer drying, sun exposure and a period of fermentation (leaves bagged while damp, so they heat and darken) push the powder toward “red”; shorter, shaded drying keeps it “green”; drying young or shade-grown leaf indoors is often sold as “white”. “Yellow” and “gold” are usually further drying or fermentation variants of the same leaf, and “Bentuangie” names a deliberately fermented process. Laboratory analyses of commercial powders have not found that these colour labels reliably predict alkaloid content; see our strains guide.

Drying is also where moisture is or is not removed. Leaf that is bagged with too much residual moisture grows mould in the sack or shipping container, and mould is where mycotoxins such as aflatoxin and ochratoxin A come from. Our lab panel includes mycotoxins for that reason.

4. Grinding and sieving

Dried leaf is ground, in small operations with hammer mills and in larger ones with industrial grinders, then sieved to a fine, consistent powder; the “micronized” or “nano” powders some vendors sell are simply finer sieve grades. Grinding is a contamination point in two ways. Metal-on-metal wear in the mill can shed nickel and other metals into the powder, which is one reason nickel appears in heavy-metal results for kratom more often than for most botanicals. And a grinder that handles many farmers’ leaf mixes batches, so a contamination problem in one lot can spread across a processor’s whole output. The 2018 salmonella outbreak in the United States, 199 cases across 41 states, could not be traced to a single source, consistent with contamination upstream of the brands that sold it.

5. Blending, naming and bagging for export

Processors and exporters blend powders to hit a colour and texture, then label them with the names the market expects. “Maeng Da” (Thai slang roughly meaning “pimp grade”), “Bali”, “Borneo”, “Malay”, “Thai”, “Hulu Kapuas”, “Sumatra” and the rest are, at this stage, product designations rather than botanical facts: the leaf for all of them typically comes from the same region of Borneo. Powder is packed in 20–25 kg sacks, often double-bagged in plastic, and documented for export. Since September 2024 Indonesian exports must meet standards for microbiological contamination, heavy metals and adulteration under Ministry of Trade regulations; a certificate from an Indonesian lab may travel with the shipment. That certificate describes the lot as it left the processor, which is useful, and is also what vendors mean when they post a “supplier COA”.

6. Import and repacking in Canada

Sacks arrive by sea or air freight and clear customs as a botanical. The Canadian vendor stores them, then weighs powder into retail bags of 25 g to 1 kg, seals them, labels them with a strain name and often a lot number, and ships orders. Repacking is the last place contamination can enter and the first place a Canadian company is responsible for the product. A vendor that tests at this stage, after repacking, and posts the result for the lot on the bag, is doing the one thing that lets a buyer check the product they actually received. A vendor that posts only the supplier’s certificate is showing the powder before it travelled, sat in storage and was handled again. Our rubric scores those differently, and our own testing buys the retail bag.

What this means for reading a certificate

• Microbial results reflect harvest hygiene, drying and storage. Salmonella and E. coli should be absent; total aerobic counts and yeast and mould have limits.
• Heavy metals reflect soil (lead, arsenic, cadmium) and equipment (nickel, sometimes chromium). River-flood soils in Borneo and wear in grinders both contribute.
• Mycotoxins reflect moisture control in drying and shipping.
• Alkaloid content reflects the leaf and the drying; mitragynine around 1–2% is typical for powder, and 7-OH should be a trace. Elevated 7-OH in a leaf powder suggests either oxidation during processing or deliberate spiking, and is a red flag either way.
• Lot numbers are what tie a certificate to a bag. A certificate with no lot number, or a bag with no lot number, cannot be matched.

Our certificate of analysis guide walks through a real report line by line, and How we test explains the panels and limits we use.

Sources

• Antara News, Indonesia officially regulates kratom trade, 9 September 2024.
• CDC, Multistate outbreak of Salmonella infections linked to kratom products, final update May 2018: 199 ill, 41 states, no single common source identified.
• US FDA, statements on kratom testing, 2018–2019, including heavy-metal findings (lead and nickel) in 30 products.
• Kruegel AC, Grundmann O. Neuropharmacology 2018;134:108–120 (alkaloid content of leaf). PubMed 28830758.
• Lydecker AG et al. Suspected adulteration of commercial kratom products with 7-hydroxymitragynine. J Med Toxicol. 2016;12(4):341–349 (elevated 7-OH in commercial products).

Frequently asked questions

Where do red, green and white kratom come from?

Mainly from drying. Longer sun drying and fermentation darken leaf toward red; shorter shaded drying keeps it green; indoor-dried or younger leaf is often sold as white. The colours describe process more than origin.

How does salmonella get into kratom?

Kratom is a hand-harvested, sun-dried agricultural leaf handled many times before packaging and is never sterile. Contamination can occur at harvest, drying, grinding or repacking, which is why microbiological testing of the finished powder is essential.

Why are heavy metals found in kratom?

Lead, arsenic and cadmium come from soil; nickel and chromium come mainly from wear in grinding equipment. US FDA testing in 2019 found lead and nickel in most products sampled.

What is the difference between a supplier COA and a retail-lot COA?

A supplier COA describes bulk powder before export. A retail-lot COA tests the powder after the Canadian vendor repacked it, with a lot number matching the bag. Only the second describes what a customer receives.