This is a difficult genus, and the species are not easy to distinguish. The nature of the beak (which develops from the style) can usually be predicted from immature fruit. However, there are an annoying number of specimens that have contradictory features, such as ± pinnatifid upper leaves or short petals, but long stylar beaks. More well made collections and work are needed here.
1. Uppermost leaves (and bracts at base of peduncles) with angular teeth but no lobes (other than basal auricles); fruit with beak ca. (1.3–) 1.5–3.1 mm long (except in the rare waif B. stricta).
2. Fruit with beak ca. (1.3–) 1.5–3.1 mm long; petals 5–9 mm long.
2. Fruit with beak ca. 0.2–1.5 (–2) mm long; petals 2.5–4.5 mm long.
1. Uppermost leaves ± pinnatifid with 1 or usually 2 pairs of narrow lateral segments; fruit with beak rarely as long as 1.5 mm.
3. Principal mid-cauline leaves with 2–3 pairs of lateral lobes; mature fruit less than 3 (–3.4) cm long; petals ca. 4–5 mm long.
3. Principal mid-cauline leaves with at least 4–5 pairs of lateral lobes; mature fruit at least 3.5 cm long; petals ca. 5–8 mm long.
All species found in Barbarea
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 11, 2017. http://www.michiganflora.net/genus.aspx?id=Barbarea.