Blue Curls Resurfaces

On a recent work trip in Muskegon County, Michigan, Linda VanAndel and I saw the State Threatened Blue Curls (Trichostema dichotomum) in bloom.  This annual mint has flowers that are small (only about 1 cm long) but that are quite interesting, with arching hair-like stamens (Trichostema in fact means "hair-like stamens") curled over the single lower lip.  Looking at the form of the flowers, you can see how the lower, purple-spotted lip serves as a nice landing pad for insects in search of nectar, while the curled stamens deposit pollen on the back of the oblivious feeding insect.  The style is also curled and arching, meaning that the next Blue Curls flower that the insect visits will be pollinated when the pollen on the insect's back rubs up against the receptive stigma.  This is an excellent pollination strategy, considering that bee species characterstically move from flower to flower of plants of the same species in search of nectar.

Blue Curls is known from many states and provinces in the eastern half of North America.  It grows in coarse, acidic soils in open areas including prairies, savannas, open woodlands, sandhills, and pine flatwoods.  Blue Curls relies on fire or other disturbance to persist as part of a local flora, as it is not tolerant of competition from other plant species.

Stable over its North American range, Blue Curls is also a species of concern in Indiana (State Rare).  The site where we saw it in Michigan was excavated a few years ago, creating disturbed, open soil that is ideal.  I have seen it at a few sites in Indiana, including one location in Porter County that historically was mined for sand and another along a recently excavated roadside berm in St. Joseph County (both, again, disturbed sandy soil).  The yet to be answered question is: where does this species come from when there is no apparent seed source and sandy soil is excavated?  Have the seeds been covered by years of sand and organic accumulation, just waiting for a disturbance to bring them back to the surface so that they can germinate?  Are the seeds brought in by excavating equipment?  My guess is the former, but then you have to wonder how long the seeds can remain viable.  Surely, it takes hundreds, if not thousands, of years for a foot or more of soil to accumulate, meaning that the seeds may remain viable for that long.  Nature is resilient.