Annual herb with a large taproot to 1 m tall Stem: upright, usually branched near the apex, sometimes purplish at the nodes, hairy on the basal one-fourth, and with a waxy coating (glaucous) above. Flowers: in compact, branched clusters (racemes), which are borne terminally and laterally on the stems. Racemes about 15 cm long. Flower stalks 7 - 8 mm long. Sepals four, upright to spreading, green, 5 - 6 mm long, 1.3 mm wide, linear, tips rounded, involute (rolled inward along the margins above). Petals four, exserted, spreading in the apical half, pale yellow, to 1 cm long, 2 - 3 mm wide at apex, spoon-shaped, bases narrowed, tips rounded. Stamens six, upright. Fruit: a long, narrow pod (silique), ascending to upright, stalks thick (nearly as thick as pods), 5 - 10 cm long, 1 - 1.5 mm wide, angled, sickle-shaped, on stalks to 1 cm long. Lower leaves: alternate, pinnately divided, stalked (purplish at base), leaf axes sparsely hairy. Segments five to eight pairs, 1 - 1.5 cm long, about 5 mm wide, awl- to lance-shaped, tips pointed, sometimes coarsely toothed and often involute (rolled inward along the margins above), shortly hairy. Terminal segments wider than the laterals and involute. Upper leaves: alternate, pinnately divided, stalked, small, leaf axes sometimes sparsely short-hairy. Segments fewer than lower leaves, about 2.5 cm long, about 1 mm wide, linear, bases often with smaller divisions, pointed at the tip, involute (rolled inward along the margins above).
Similar species: No information at this time.
Flowering: mid-May to mid-October
Habitat and ecology: Introduced from Eurasia. Frequent on railroad ballast. It also grows in waste ground and recently disturbed sandy soils.
Occurence in the Chicago region: non-native
Etymology: Sisymbrium is the Ancient Greek name for various plants. Altissimum means very tall; tallest.
Erect, to 1 m, commonly simple below and much-branched above, glabrous or sparsely pilose; lvs petioled, pinnatifid, the lower with 5-8 pairs of linear and entire to lanceolate and serrate segments, the upper small, with fewer segments; pet pale yellow, 6-8 mm; pedicels nearly or quite as thick as the fr, ascending, 5-10 mm; frs ascending or spreading, slender, 5-10 cm נ1-1.5 mm; 2n=14. Native of Eurasia, established as a weed of fields and waste places throughout most of the U.S. and adj. Can., especially northward. June-Aug. (Norta a.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
ERI 2003, Kearney and Peebles 1969, USDA FEIS accessed 2015, FNA
Duration: Annual Nativity: Non-Native Lifeform: Forb/Herb General: Weedy annual herb with stems 30-150 cm tall, generally highly branched, hirsute up to the inflorescence. Leaves: Basal leaves petioled, 7-15 cm long, deeply pinnately lobed with lanceolate segments. Stem leaves alternate, gradually reduced, petioled, deeply pinnately lobed with linear segments near top. Flowers: Raceme with sepals 4-5 mm long, outer two with erect horns, petals 5-9 mm long, pale yellow to nearly white. Fruits: Spreading siliques, linear and cylindric, 5-10 cm long, about 1 mm wide, branch-like. Ecology: Found in disturbed sites from 3,000-8,000 ft (914-2438 m); flowers April-September. Distribution: Native to Eurasia and natualized throughout most of the US and Canada. Also occurs in Africa and South America. Notes: This annual weed is distinguished by large, deeply pinnately lobed basal leaves and very narrow, delicate leaves on the upper part of the stem; long, narrow fruits that are only about as wide as their pedicels (fruiting stalks); and pale, cream or white colored flowers. S. irio is common annual weed in the genus; it has yellow flowers, is not as tall, with a maximum height of about 0.7 m, and the cauline leaves are the same size and shape as the basal leaves, or only a little reduced in size. S. linifolium also has yellow flowers, generally is not taller than 0.7m, and has much smaller leaves than S. altissima. Ethnobotany: Used as an emetic and the seeds were eaten in a porridge. Etymology: Sisymbrium is from a Greek name for some plants of the mustard family, while altissimum means very tall, or tallest. Synonyms: Norta altissima Editor: SBuckley, 2010; AHazelton 2015