Sisymbrium irio

Annuals; glabrous or sparsely pubescent. Stems erect, branched proximally and distally, (1-)2-6(-7.5) dm, glabrous or sparsely pubescent at least basally. Basal leaves not rosulate; petiole (0.5-)1-4.5(-6) cm; blade oblanceolate or oblong (in outline), (1.5-)3-12 (-15) cm × (5-)10-60(-90) mm, margins runcinate to pinnatisect; lobes (1-)2-6(-8) on each side, oblong or lanceolate, smaller than terminal lobe, margins entire, dentate, or lobed. Cauline leaves similar to basal; (distalmost) blade (smaller, to 2 cm wide), margins entire or 1-3-lobed. Fruiting pedicels divaricate or ascending, slender, much narrower than fruit, (5-)7-12(-20) mm. Flowers: sepals erect, oblong, 2-2.5 × 1-1.5 mm; petals oblong-oblanceolate, 2.5-3.5(-4) × 1-1.5 mm, claw 1-1.5 mm; filaments 2.5-4 mm; anthers ovate, 0.5-0.9 mm. Fruits (divaricate to ascending, young fruits overtopping flowers), narrowly linear, straight or slightly curved inward, slightly torulose, slender, (2.5-)3-4(-5) cm × 0.9-1.1 mm; valves glabrous; ovules 40-90 per ovary; style 0.2-0.5 mm; stigma prominently 2-lobed. Seeds 0.8-1 × 0.5-0.6 mm. 2n = 14. Flowering Dec-May. Rocky slopes, orchards, roadsides, fields, pastures, waste grounds, prairies, disturbed sites; 0-1700 m; introduced; Ariz., Calif., Colo., Conn., Fla., Idaho, Mass., Mich., Nev., N.Mex., Ohio, Pa., Tex., Utah, Wyo.; Europe; w, c Asia; n Africa; introduced also in South America, Australia.

Erect, to 6 dm, spreading-hairy below; lower lvs deeply pinnatifid with oblong to ovate, entire to dentate or angularly lobed segments, the upper lvs with fewer and smaller lobes; infl very contracted, the young frs elongating rapidly and projecting beyond the fls; sep 2-3 mm; pet 3-4 mm; anthers ca 0.7 mm; pedicels slender, divergent, 5-10 mm; frs linear, 2.5-5 cm; 2n=14, 28, 42, 56. Native of Eurasia, occasionally found in our range, and becoming a weed in the Pacific states. May, June. (Norta i.)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.

Martin and Hutchins 1980, Kearney and Peebles 1969, Correll and Johnston 1970, FNA 2010, USDA GRIN, Heil et al 2013

Duration: Annual Nativity: Non-Native Lifeform: Forb/Herb General: Annual herb, up to 75 cm tall, from a taproot; stems erect, branching from base and above; herbage glabrous to sparsely pubescent. Leaves: Basal leaves petiolate, not arranged in a rosette; stem leaves alternate, petiolate; blades oblanceolate or oblong in outline, 3-12 cm long, pinnately divided into 2-6 pairs of lobes; margins entire, dentate, or lobed; uppermost stem leaves sometimes not lobed. Flowers: Yellow, in usually several terminal racemes per plant; pedicels ascending, 5-14 mm, slender, much narrower than the fruit; sepals 4, green; petals 4, 3-4 mm long, yellow; Fruits: Capsules linear, slender, < 1 mm in diameter, 2-5 cm long, curving upward. Seeds oblong, yellow, less than 1 mm long. Ecology: Fairly widespread weed of all disturbed areas below 4,500 ft (1372 m); flowers February-May. Distribution: Native to the Asia and the Mediterranean; now found throughout the world. In the US from CA, NV, AZ, UT, CO, NM, TX, the midwest and FL. Notes: Introduced from Eurasia, this is an abundant weed distinguished by being an erect annual with mostly glabrous foliage; pinnately lobed leaves with broad lobes which are not filiform; yellow flowers and elongated, slender, linear, terete fruits 3 cm or longer with a very small thickened section near the end. The common name London rocket is misleading, as this plant is also an introduced species in the British Isles. Distinguish from S. altissimum based on the fruiting pedicels, which are slender on S. irio and stout on S. altissimum, about the same width as the seed pod. Ethnobotany: Used by the Pima as food. Seeds were parched and made into pinole and leaves were eaten raw, boiled, or fried. Etymology: Sisymbrium is from sisymbrion, an ancient Greek name referring to a number of different mustards; irio is a reference to an old kind of cress. Editor: SBuckley 2010, FSCoburn 2015, AHazelton 2015, AHazelton 2017