Flixweed, Descurainia sophia (L.) Webb ex Prand, is a native North American taxon. It is very similar to tansy-mustard, D. pinnata (Walt.) Britt., an Old World species, and is often confused with it. Flixweed can be distinguished from tansy mustard by its glandular hairs, seeds in two rows in each half of the silique (a two-carpelled fruit peculiar to the Cruciferae), and siliques about 15 to 30 mm long on stalks 7 to 12 mm long (6, 17). Tansy mustard, on the other hand, has leaves divided into fine segments and shorter siliques, 12 mm long, on stalks of nearly the same length. Tansy mustard, introduced from Europe, has become well established throughout the U.S., Canada, and Alaska (5). Depending on circumscription, there are nine native North American species and 17 subspecies of Descurainia. In a recent work, D. J. Mabberley (13) states that there are 55 species. They are extremely variable. Their center of distribution is in the southwestern U.S., and the least stability of characters is found here. Most of the species presumably originated in this region (5).
Whence the name flixweed? Formerly, D. sophia was a supposed remedy for flux or dysentery. In 1742 flux first appeared in print in the English language in the 4th edition of London and Country Brewer: "Brewers servants ... formerly scorned what they call Flux Ale." Flux ale is likely to cause diarrhea and fluxweed was prescribed as a treatment. Flixweed, of course, is a corruption of fluxweed and perhaps was considered a more socially acceptable name, especially when it was demonstrated that the plant did not cure dysentery (22). E. J. Salisbury (21) offered a different explanation for the name. Since the weed also was used in helping to mend broken limbs, it was called flux-weed, i.e., it was applied to bones to fuse them together. In 17th century England, flixweed was a very common plant of waste ground. Gerard states that it "groweth inmost places of England almost everywhere in ruins of old buildings by high wales and in filthie obscure base places" (21).Other common names for flixweed are herb-sophia and fine-leaved hedge mustard (2).
HISTORY AND ETYMOLOGY
Descurainia is in the Cruciferae (mustard family), a large natural family (about 380 genera and some 3000 species) of major economic importance, containing a wide array of crop plants grown as salads, vegetables, for oil-seed, animal feed, and condiments, and several well-known garden ornamental plants such as wallflower, honesty or money plant (Lunaria annua), and aubretia. It also contains numerous weeds (10). The genus Descurainia is named for French botanist F Decourain (1658-1740). Relationships and characters of species are difficult within the genus (11). The type species is D. sophia. The species name, sophia, means wisdom, an allusion to its reputed medicinal properties (7). Originally D. sophia was named Sisymbrium sophia by Linneanus in Species Plantarum, in 1753, and earlier American botanists also included descurainias in that genus. But in 1763, the genus was reclassified as Sophia by Michel Adanson (1727-1806) in Familles des Plantes. Some systematists held that the presence of branched pubescence in this group of species, combined with certain other rather distinctive characters, warranted that it should be considered a separate genus (5). Consequently, a third major classification occurred in 1892. Philip Barker Webb (1893-1854) designated it as Descurainia sophia, and it was published eventually by Karl Prand in Adolph Engler and Karl Prand's Die Natiirlichen Pflanzenfamilien.
However, Nathaniel Lord Britton (1859-1934) and Addison Brown (1872-1913) restored Adanson's old name of Sophia sophia (2) in vol. 2 of their 1897 publication, An Illustrated Flora of the United States, Canada and the British Possessions. This is the earliest reference in scien-tific literature to any of the native North American species of Sophia (5).The first extensive treatment of the species in a flora was that by John Torrey (1796-1873) and Asa Gray (1810-1888) in A Flora of North America published in 1840 (27). With the exception of the introduced Sisym-brium sophia and the arctic and subarctic S. sophioides, these authors listed and described all of the American forms known to them as six varieties of Thomas Nuttall's S. canescens (5). Later Eugene Pierre Nicholas Fournier (1834-1884) made an extensive study of the genus Sisymbrium (sensu lato), incorporating the results in Recherches sur les Cruciferes, published in 1865. The Pacific Coast species were treated by Sereno Watson (1826-1892) in 1871 in the Botany of the King Expedition, and again in 1876 in William Henry Brewer (1828-1910) and Sereno Watson's Botany of California (5). An exhaustive monograph of Descurainia (40 species) is included in Cruciferae-Sisymbrieae by O. E. Schulz in Das Pflanzenreich, 1924.
In 1840 flixweed was found near Quebec, Montreal, and in other parts of Canada (28) and was considered a Canadian native. In actuality it moved across Europe with human migration and reached Canada with the French settlers (1). The earliest specimens (1901) in the Ottawa herbarium are from Manitoba and Saskatchewan (1). Willis L. Jepson (1867-1946) collected flixweed al Yreka, California, in 1908 (20). It was introduced intc North Dakota about 1910. In 1933 John Thomas Howell (1903-1994) collected it on the sandy open Mojave Desert in Kern County; it was the first record of the plant it Southern California.
Annual or winter annual, usually with an aromatic but rank odor, the whole plant grayish-green due to minutely branched, forked or starlike hairs; stems 2 to 10 dm high, commonly branching; fern-like leaves are alternate, finely dissected two to three times; flowers clustered at top of stem, petals whitish to yellow, 2 to 2.5 mm long and not longer than the sepals; siliques narrowly linear, 15 to 30 mm long, 0.5 to 1.0 mm wide ascending at right angles to the stem on short stalks 7 to 12 mm long; seeds 10 to 20 in one row in each half of the silique, oblong-ellipsoid, bright orange, about 0.8 mm long (9, 14, 17).
In addition to Canada and the U.S., where it is widely established, flixweed is native throughout temperate Europe to 65° latitude, and is also found in Iran, Russia, Turkey, South Africa, North Africa, in Asia from Kashmir to Kumaon and extending to Buluchistan and to China and Japan, and in Argentina and New Zealand (4, 12). In Europe, flixweed is found primarily on open, warm, nutrient-rich sandy or stony soils; it is often an indicator of sand (8). After World War 11, it frequently occurred in the rubble of bombed cities where ecological aspects were favorable (18). In North America, flixweed ranges from Quebec to Washington, south to Delaware, New York, Illinois, Missouri, Kansas, and California, being more common in eastern Oregon, Washington, and the Great Basin region (14, 15). A likely distribution was from ballast deposited around northern seaports (2). Flixweed is a troublesome weed in cultivated lands, grain fields, disturbed areas, city streets, roadsides, and waste places. In the southwest it is found in moist spots on sandy, rocky, or disturbed soil of riverbeds, washes, mesas, canyons, slopes, and swales in creosote desert, grassland, sagebrush, oak, and pinyon-juniper associations (9, 17). In California it is found mostly above 2700 m (11).
GROWTH HABIT AND WEEDINESS
In northern grain-growing areas, flixweed is generally associated with field pennycress (Thlaspi arvense L.), especially on uncultivated fields in fall. It may overwinter as seeds in the soil or as compact rosettes. The low, rosette habit of flixweed protects overwintering plants from low temperatures and drying winds, enabling them to gain maximum advantage from the insulating effect of snow cover (1). Rosettes may vary in size and number of leaves depending on their stage of development at freeze-up. On summer fallow land in the fall, flixweed seedling stands are very dense at times, resulting in stunted growth (1). Flixweed is not as competitive with small grains as is wild mustard (Sinapis arvensis L.), another widespread crucifer (3). However, an extra cultivation is needed frequently in the spring to control rank growth from heavy infestations of overwintering flixweed. The competition crowds out the crop plants and reduces yields (16). In the spring the plants rapidly develop numerous leaves and up to 15 lateral branches. If growing conditions are favorable, the racemose inflorescence and the plant's capacity to produce numerous additional inflorescence from lateral branches largely explain its prolific seed production (1).
The average date of first flowering in North Dakota is 28 May, and flowering continues throughout the summer (25). The estimated average number of seeds from a single plant is 75 650 (24), but one large plant may produce 700 000 seeds (21). O. A. Stevens recorded a maximum seed population of 704 582/mz in a North Dakota soil (26). At harvest, many flixweed seeds are scattered in the vicinity of the parent plants, while others are included as impurities in cereal and forage seed (23). Seed germination averages about 70% and seeds can retain their viability for considerable periods in the soil. This probably accounts for the curious fact that the 17th century botanist Morison held the belief that this weed could develop spontaneously without seeds (21). Flixweed seeds are spread by wind, animals, and man. Mucilaginous seeds may become attached to the feathers of birds feeding in infested areas and are moved into new areas by preening (21).
Species of Descurainia resemble each other closely and probably all of them can be used as food in the same way. Flixweed has been used, particularly by Native Americans, as a source of seed for making pinole. They pounded the dry pods in various ways, and the accumulated seeds were then parched and ground into a meal. This was cooked into a mush, made into bread or used to thicken soup. While it may be rather tedious to gather a sufficient quantity of seeds, flixweed is so abundant that it may be used in certain local areas (9). Native Americans used the young tender growth of flixweed as a potherb, often baking it in a firepit lined with stones. By piling alternating layers of the greens and hot stones, then covering the top, they were able to secure a kind of fireless cooker. They let the plants steam for about 30 min and used them at once, or let them dry out for future use. Compared to boiling, this method produced a better product (9).When sampled raw, flixweed's scent and bitter taste repel many people. To prepare, boil fresh plants for 3 or 4 min, with two changes of water. This removes some of the objectionable smell and taste, but a lingering, bitter after-taste remains; a taste must be acquired for flixweed. How-ever, it can be considered an emergency food, largely because of its abundance (9). Flixweed is used as minor oil-seed crop (13). Its pun-gent seeds are occasionally made into a mustard (19). Flixweed seeds are exported from Shanghai and Hankow to Chinese pharmacies, and are considered to be demulcent (a mucilaginous substance capable of soothing or protecting an abraded muscos membrane), laxative, and antipyretic (reduces fever). The fatty oil from the seeds contains linolenic, linoleic, oleic, erucic, palmitic, and stearic acids. Additional oils are obtained from steam-distillation of the seeds (19). Whether its prevalence is due in part to its cultivation as a medicinal herb is doubtful (21).
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