Wormseed mustard (Treacle-mustard)
Erysimum cheiranthoides

General Description: Annual or winter annual, reproducing only by seed. It is distinguished from other mustards by its slender leaves which do not clasp the stem, the 2-branched hairs on the stems and 3-branched hairs on leaves which can be seen with magnification, a slightly bluish-green cast to leaves and stems, the small, pale yellow flowers, and the slender, angular seedpods about 2 cm (4/5 in.) long which are tipped with a short blunt beak.
Stems & Roots: Stems 15 - 100 cm (6 - 40 in.) high, erect, usually branched, firm, apparently hairless but slightly rough due to tiny, flat-lying, 2-branched hairs; leaves alternate (1 per node), nearly linear or broader near the middle and tapering to both ends, without teeth or with a few wavy or slightly pointed teeth, slightly rough on both surfaces with tiny 3-branched hairs.
Flowers & Fruit: Flowers similar to those of Wild mustard but paler yellow and much smaller, about 6 mm (¼ in.) across and crowded in clusters at the ends of the stems and branches, these lengthening as the pods begin to develop; seedpods on slender stalks about 1 cm (2/5 in.) long which stand out from the stem, the pod itself standing upwards or nearly parallel to the stem, 15-25 mm (3/5-1 in.) long, usually somewhat 4-angled in cross-section and tipped by a short blunt beak; seeds dull reddish-yellow, very small, about 1 mm (1/25 in.) long and usually less than half as wide. Flowers from mid-June to late autumn and sheds mature seeds soon after flowering begins; plants often turning purplish at maturity.
Habitat: Wormseed mustard is common throughout Ontario, growing in a very wide variety of habitats from dry, rocky, shallow soils to moist sandy shores, to rich loam and clays, and is found in grainfields, hay and pastureland, waste places, gardens, poorly kept lawns, roadsides and railways, riversides, sandy beaches and limestone talus.