Treacle Mustard

Records in FRPS of Erysimum cheiranthoides from provinces and autonomous regions other than the ones listed above are likely based on misidentified plants of E. macilentum. The two species are quite distinct and are easily distinguished by the characters in the above key.

Although the present authors have not examined the type of Erysimum brevifolium, it is almost certain that the species is a synonym of either E. cheiranthoides or E. macilentum because in the protologue the interior of the fruit valves was described as densely stellate. It is here placed in the synonymy of E. cheiranthoides based on the shape of the petals, which were said to be narrowly obovate; in E. macilentum the petals are linear to linear-oblanceolate.

Herbs annual, (7-)15-100(-150) cm tall. Trichomes primarily 3- or 4-fid, sometimes mixed with 5-fid ones, malpighiaceous trichomes primarily on stem and pedicels. Stems erect, often branched above, ribbed. Basal leaves rosulate, withered by fruiting. Middle and upper cauline leaves shortly petiolate or sessile; leaf blade lanceolate, linear, or elliptic-oblong, (1-)2-7(-11) cm × (2-)5-10(-20) mm, base cuneate, margin subentire or denticulate, rarely sinuate-dentate, apex acute or obtuse. Racemes corymbose, densely flowered, ebracteate, elongated considerably in fruit. Fruiting pedicels divaricate or ascending, 5-13(-16) mm, slender, much narrower than fruit. Sepals oblong, 1.8-3 × 0.5-1 mm, not saccate. Petals yellow, narrowly spatulate, 3-5 × 1.5-2 mm, apex rounded; claw distinct, subequaling sepals. Filaments yellow, 2-3.5 mm; anthers oblong, 0.5-0.7 mm. Ovules (20-)30-55 per ovary. Fruit linear, 4-angled, (1-)1.5-2.5(-4) cm × 1-1.3 mm, somewhat torulose, suberect or divaricate-ascending, straight; valves with a distinct midvein, outside with 3-5-forked trichomes, inside densely pubescent; style slender, 0.5-1.5 mm, cylindric; stigma slightly 2-lobed. Seeds oblong, 1-1.5 × 0.4-0.6 mm. Fl. May-Aug, fr. Jun-Sep. 2n = 16.

Heilongjiang, Jilin, Nei Mongol, Xinjiang [Japan, Kazakhstan, Korea, Mongolia, Russia; N Africa, Europe, North America].

Dry beds, moist areas; 800-3000 m.

Erysimum brevifolium Z. X. An; E. cheiranthoides var. japonicum H. Boissieu; E. japonicum (H. Boissieu) Makino; E. parviflorum Persoon.