Hemp fiber comes from the stalk of the industrial hemp plant (Cannabis sativa), specifically from a layer of long, strong fibers just beneath the outer bark. These outer fibers, called bast fibers, make up roughly one-third of the stalk by weight and are the primary source of the material used in textiles, paper, and composites. The remaining two-thirds of the stalk is a woody inner core called hurd or shiv, which has its own set of uses.
The Two Parts of the Hemp Stalk
If you were to cut a hemp stalk in cross-section, you’d see two distinct layers. The outer layer, sitting just under the bark, contains bundles of bast fibers. These fibers are 57% to 77% cellulose with relatively low lignin content (5% to 9%), which makes them flexible, strong, and well suited for spinning into yarn or pressing into sheets. They’re considered the strongest and longest natural fiber available, outlasting cotton and costing less to produce.
The inner core is the hurd: a lightweight, woody material made of shorter fibers with a different chemical profile. Hurds contain 40% to 48% cellulose but significantly more lignin (21% to 28%), giving them a stiffer, more wood-like character. For decades, hurds were treated as low-value waste. Today they’re used in animal bedding, insulation boards, and hempcrete, a carbon-negative building material with strong thermal insulation properties.
How the Plant Grows
Industrial hemp grows fast. Planted in spring, it reaches harvest maturity in roughly 70 to 100 days, typically by late August or early September. The plants grow densely and tall, which encourages long, straight stalks with minimal branching. This growth habit is ideal for fiber production because it maximizes the length of usable bast fiber per stalk. Varieties bred specifically for fiber tend to have thinner stalks with a higher proportion of bast to hurd, sometimes reaching up to 48% bast fiber by mass, though 30% is more typical.
Separating the Fiber: The Retting Process
Getting usable fiber out of a hemp stalk requires breaking down the pectin, a natural glue that binds the bast fibers to the woody core and to each other. This process is called retting, and it’s the most critical step in determining fiber quality.
Dew retting is the oldest and simplest method. Cut stalks are spread across a field and left for several weeks. Morning dew, rain, and naturally occurring microorganisms slowly break down the pectin. It’s low-cost but hard to control: too little time and the fibers won’t separate cleanly, too much and they start to weaken.
Water retting produces more consistent results. Stalks are submerged in tanks or ponds where bacteria that specialize in breaking down pectin flourish in the warm, wet environment. Research from lab-scale water retting trials shows a strong spike in pectin-degrading enzyme activity between 14 and 21 days of submersion. Interestingly, stalks that go straight into water retting without any prior field exposure develop a more uniform population of these pectin-eating microbes, which leads to higher enzyme activity and more even fiber separation.
Enzyme retting is a newer approach that applies commercially produced enzymes directly to the stalks, cutting processing time and giving manufacturers tighter control over fiber quality. It’s more expensive, but it produces the cleanest, most uniform fibers for high-end textile applications.
After retting, the stalks go through mechanical processing. They’re crushed to break the woody core, then scutched (scraped) to separate the bast fibers from the hurd pieces. Finally, the fibers are hackled, or combed, to align them and sort them by length.
Bast Fiber vs. Hurd Uses
The long bast fibers are the high-value product. Aligned long fibers are spun into yarn for clothing and woven textiles. Hemp fabric is breathable, UV-resistant, and naturally antimicrobial. Testing has shown hemp garments provide thermal comfort nearly identical to conventional long-sleeve clothing standards. Shorter or less uniform bast fibers go into non-woven fabrics, paper, or composite reinforcement materials for automotive panels and biocomposite boards.
Hemp has been used to make paper for centuries, and its high tensile strength makes it an ideal non-wood raw material for specialty papers. In the composites industry, hemp fiber’s length and strength make it a strong candidate for reinforcing biodegradable plastics and thermoplastic packaging. Chopped hemp stalks, including both bast and hurd material, are also pressed into particle boards and insulation panels with densities ranging from 300 to 1,100 kg/m³.
How Hemp Compares to Cotton
One reason hemp fiber is attracting renewed attention is its environmental profile. A comparative study drawing on 28 published sources found that hemp requires 38% less water overall than cotton, has a 60% lower water footprint, needs 84% less irrigation, and carries a 91% lower irrigated water footprint. Hemp also grows well without heavy pesticide use, partly because its dense canopy shades out weeds and its natural compounds deter many pests.
Long fiber yields from hemp fields typically range from 0.6 to 1.4 tons per hectare, and the crop reaches harvest in a single growing season. Cotton, by comparison, demands far more water and chemical inputs to achieve comparable textile output.
Legal Classification
Industrial hemp is legally distinct from marijuana based on its concentration of THC, the psychoactive compound. In the United States, the legal threshold is less than 0.3% total THC on a dry weight basis. A 2025 amendment (P.L. 119-37) updated this definition to cover total THC rather than only the delta-9 form, closing a regulatory gap. Hemp and hemp-derived products at or below this limit are not classified as controlled substances, which means fiber hemp can be grown, processed, and sold commercially throughout the country.