Descurainia sophia (L.) Webb ex Prantl. (Sisymbrium Sophia)
Annual Broad-leaved Weeds
Flixweed is an annual, overwintering or rarely biennial herb, possibly native or a long-term introduction. It was a common plant of waste ground in the 17th century but is now uncommon and scattered through England and Wales. In a survey of arable weeds 1971-73, it was found in less than 2% of the areas surveyed. It is found on sandy and peaty soil in East Anglia and is said to be an indicator of sand. The Breckland area of East Anglia is the centre of distribution. Flixweed is not recorded above 1,000 ft in Britain.
Flixweed flowers from May to October. The average seed number per plant ranges from 6,000 to 75,650. A large plant can produce 700,000 seeds but in a competitive cereal crop a plant may have just 150 seeds. Seed matures early and the pods shatter easily.
Seed germination occurs only in the light or following a light flash. Nitrate promotes germination. Flixweed seed germinates in spring and autumn. There are peaks of emergence in April-May and September.
Persistence and Spread
Flixweed seed can probably retain viability for long periods. Seeds recovered from house demolitions and dated at 20-30 years are reported to have germinated. Seed buried in soil under sub-arctic conditions had 3% viability after 9.7 years. Dry-stored seed gave 3% germination after 5 years. Flixweed seeds submerged in water gave 8% germination after 6 months.
Seed has been found as an impurity in cereal and forage seeds. Flixweed seeds become mucilaginous when moistened. The seeds are spread by wind, animals and by man. Seed has been recovered from irrigation water. Ensilage for 8 weeks, rumen digestion for 24 hr or a combination of both killed most seeds but up to 3% remained viable.
Seedlings that emerge in the autumn can be controlled by autumn or early spring cultivations.
Updated October 2007.