In early April I made a trip down to extreme southern Indiana with Mike Homoya and Roger Hedge to see a unique spring ephemeral native mustard in bloom. Our target was Michaux's Gladecress (Leavenworthia uniflora), and we weren't disappointed. We met up with Jason Larson and Derek Luchik to see this little gem.
Michaux's Gladecress is a tiny plant, with the largest specimens only reaching about seven inches tall when in flower; most plants are much shorter than this. As an annual calciphile that can't tolerate competition from other plants, Michaux's Gladecress is restricted to areas with limestone at or near the surface, such as glades, rocky old fields, roadsides, and rocky ledges. In Indiana, this habitat is only found in the southeastern part of the state, near the Ohio River.
Limestone glades aren't common in Indiana, and as a result Michaux's Gladecress isn't common in the Hoosier State. Even within the glades that are present, this little mustard is really only found in areas of nearly bare soil; it is more common in areas with exposed limestone that are near but not in the glades. In areas meeting this description, the species can be rather abundant, growing in tiny cracks in the limestone or areas where a miniscule amount of soil has accumulated.
Michaux's Gladecress is only known from Missouri, Arkansas, Alabama, Georgia, Tennessee, Kentucky, Ohio, and Indiana. In Indiana, its populations are restricted to Clark County, and as a result it is listed as endangered; globally it is apparently secure (G4).
What a great way to start off the botanical year!