6. Linum usitatissimum L. (common flax)
Pl. 447 g, h;
Map 2023
Plants annual,
Stems 25–80 cm long, solitary or more commonly several, glabrous, usually with
fine longitudinal lines but not prominently ridged (circular in cross-section).
Leaves alternate. Stipules absent. Leaf blades 2.5–3.0 cm long, 3–5 mm wide,
linear-elliptic, narrowed or tapered to a sharply pointed tip, the margins
entire. Sepals 7–9 mm long, ovate, those of both whorls with the margins thin
and entire, those of the inner whorl often with minute spreading hairs. Petals
10–15 mm long, blue. Styles distinct, 2.5–5.0 mm long. Fruits usually tardily
dehiscent, often remaining on the plant for some time after maturity, 7–10 mm
long, 6–9 mm in diameter, ovoid to subglobose, breaking into 10 mericarps, each
1-seeded, rounded across the dorsal surface, the septa glabrous or occasionally
sparsely hairy along the ventral margins, the mature fruits lacking purple
stripes. Seeds 4–6 mm long, brown. 2n=30. May–September
Introduced,
uncommon and sporadic, mostly in eastern and southwestern Missouri (an Old
World cultigen unknown from natural populations, introduced nearly throughout
North America). Roadsides, railroads, old fields, and open disturbed areas.
Common flax has
an extremely long history of cultivation. It is not widely grown in Missouri,
but is a common crop plant in the northern states from Minnesota to Montana.
The seeds of flax are the source of linseed oil, and they are also a minor
component of some animal feeds. They are also an ingredient in some bird seed
mixes, which may be how some of the recently collected populations in Missouri
became established. Linseed oil formerly was important as a drying agent in
inks and paints, and in the manufacture of linoleum, varnishes, and soaps.
Today it is no longer commonly used in human foods, but is still occasionally
used in medicinal preparations. The stem fibers are used in linen cloth and
sometimes also in canvas, thread, twine, paper (including cigarette rolling
papers, fine writing papers, legal documents, and paper currency), and carpet
material (Steyermark, 1963).