Our common species, Corydalis aurea, plus also Capnoides sempervirens, share an interesting ecological situation with a few other plants, such as Chenopodium capitatum and Leucophysalis grandiflora. These are most typical of disturbed ground (especially sand and calcareous gravels) at previously forested sites about 1-3 years after disturbance (clearing, bulldozing, fire, pasturing, etc.). Unless the area continues to be disturbed, these species quickly retreat back into the soil seed bank. On rock outcrops, shores, and places where soil is disturbed by erosion or overthrown tree roots, there are more natural niches for some of these species than the easily noticed human-disturbed ground.

An Asian species, Corydalis incisa, a tuberous rooted biennial with racemes of purplish flowers and finely dissected leaves, can become a pest in gardens where accidentally or purposely introduced, and will very likely become established in southern Michigan. It can be distinguished from the perennial C. solida, also purple flowered, by the first year vegetative rosettes noticable in populations, its larger size, and its relatively thick, fleshy upright stem with evident cauline leaves. Two European species of Pseudofumaria, P. alba and P. lutea with white and yellow flowers respectively, look rather like Corydalis and are sometimes cultivated. They seed readily into settings with bare soil and may appear as weeds in gardens and disturbed areas nearby. They are fleshy branched, short-lived fibrous rooted perennials easily distingiuished from Corydalis by their deciduous stigmas, leaving the capsules blunt-tipped.

1. Plants perennial from a conspicuous, round corm; flowers purple.

C. solida

1. Plants tap-rooted, biennial or winter-annual (or sometimes annual); flowers yellow.

2. Mature flowers (10-) 11-14 mm long, including a spur ca. (2.5-) 3.5-4 mm long; seeds very smooth and shiny.

C. aurea

2. Mature flowers 7-10 (-11) mm long, including a spur ca. 1-1.5 (-2) mm long; seeds shiny but reticulate.

C. flavula