Erysimum

1. Petals ca. 18–24 mm long, (4–) 6–9 mm broad.

E. capitatum

1. Petals much smaller (less than 11 mm long and 4 mm broad).

2. Sepals 2.2–3.2 mm long; petals 3.5–5 (–5.5) mm long; fruit 1.5–2.5 cm long, ca. 2–3 times as long as the distinctly more slender pedicels; hairs on upper surface of leaves mostly 3- and 4-pronged.

E. cheiranthoides

2. Sepals (4–) 4.5–6.5 (–7.5) mm long; petals (6–) 7–9 (–10) mm long; fruit 2.5–8 cm long, ca. (5–) 6–20 or more times as long as the thick pedicels (nearly as thick as the fruit); hairs on upper surface of leaves various.

3. Fruit ca. 5–8 cm long, widely spreading; leaves remotely denticulate or shallowly sinuate, without 4-pronged hairs (all 2- and 3-pronged); plant annual, usually many-branched.

E. repandum

3. Fruit 2.5–5 cm long, strongly ascending or erect; leaves entire and without 4-pronged hairs or toothed and with 4-pronged hairs above; plant biennial or perennial, usually stiffly erect and unbranched.

4. Cauline leaves remotely toothed or denticulate, elliptic-lanceolate, often more than 5 mm broad, with both 3- and 4-pronged hairs above.

E. hieraciifolium

4. Cauline leaves entire, essentially linear, up to 5 mm broad, without 4-pronged hairs (all 2- and 3-pronged).

E. inconspicuum

All species found in Erysimum

Erysimum capitatumWESTERN WALLFLOWER 
Erysimum cheiranthoidesWORMSEED MUSTARD 
Erysimum hieraciifoliumTALL WORMSEED MUSTARD 
Erysimum inconspicuumSMALL WORMSEED MUSTARD 
Erysimum repandumTREACLE MUSTARD 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 28, 2017. http://michiganflora.net/genus.aspx?id=Erysimum.