Bast fiber

Bast fibres are the long, strong fibres that run up the outer bark of the hemp stalk, within the tissue layer botanists call the phloem. They are the part of the plant prized for textiles and cordage, and rank among the longest and strongest natural plant fibres known.

Because the bast sits on the outside of the stem and is bound to the inner woody core (the hurd) by natural pectins, it has to be separated before use. That is done by retting — letting microbes or moisture break down the binding pectins — followed by mechanical decortication to strip the fibre from the core.

Once cleaned, bast fibre is graded by fineness. Longer, finer line fibre goes into textiles, rope and twine; shorter tow fibre is used in paper, insulation, and increasingly in composite materials that can replace fibreglass in cars and panels.

Bast typically makes up only a minority of the stalk's mass — the woody hurd is the larger fraction — so the economics of a fibre crop depend on finding good uses for both streams.