Linum usitatissimum L. (origin uncertain) – A very common but ephemeral escape from or relic of cultivation, birdseed alien, etc. First subspontaneous occurrences go back to at least the beginning of the 19th century (probably much longer). Linum usitatissimum is still more or less widely cultivated in Belgium and is commonly seen by road verges, on dumps, etc. It is furthermore frequently introduced from abroad as an oilseed crop, mainly for cattle fodder and as birdseed. Hence, Linum usitatissimum is a common plant in port areas or other places where seeds are transloaded or transported (it readily germinates from spoiled seeds).
Despite being a common alien it never seems to become naturalized in western Europe (see also Sell & Murrell 2009).
Two more or less distinct varieties can be distinguished (Sell & Murrell 2009). The plant cultivated for its fiber (linen) is var. usitatissimum (flax). It has single stems up to 90 cm tall (only branched in upper part) and indehiscent capsules with more or less glabrous septa and dark seeds. Var. crepitans Boenn. (linseed) is a smaller plant (up to 40 cm) with several stems often branched to base, subdehiscent capsules with ciliolate septa and paler seeds. Both varieties surely occur in Belgium but they have not been investigated yet.
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Selected literature:
Basu N.C. & Bose S. (1975) Preliminary studies on some botanical, anatomical and agronomical aspects of flax (Linum usitatissimum L.). Sci. Cult. 41(7): 323-325.
Kulpa W. & Danert S. (1962) Zur Systematik von Linum usitatissimum. Kulturpflanze 3: 341-388.
Nair P.K.K. & Sharma R.K. (1975) A study of the pollen morphology of some cultivars of Linum usitatissimum Linn. New Bot. 2(3-4): 135-147.
Sell P. & Murrell G. (2009) Flora of Great Britain and Ireland. Vol. 3 Mimosaceae – Lentibulariaceae. Cambridge University Press, Cambridge: XXVIII + 595 p.
Seegeler C.J.P. (1983) Oil plants in Ethiopia, their taxonomy and agricultural significance. Addis Ababa, College of Agriculture and Wageningen, Agricultural University: 368 p.
Seegeler C.J.P. (1989) Lectotypification of Linum usitatissimum L. (Linaceae): a rectification. Taxon 38: 277-278.