Carpet of blue-eyed-Mary (Collinsia verna) at Russ Forest, Cass County, MI. 18 April 2010.
Collinsia verna has been collected from 13 counties in southern Michigan:
Michigan Flora Online: http://www.michiganflora.net/home.aspxI am aware of fewer than ten sites that currently support this species in Michigan, most of them in Berrien and Cass counties, with additional locations in Kalamazoo, Lenawee, and Eaton counties. The historical literature reveals additional sites that are likely no longer extant. For example, Emma Cole, in her 1901 Grand Rapids Flora, indicated blue-eyed-Mary was "abundant and local" in the Grand Rapids area, occurring at several places along the Grand River. Although I have not searched these locations, at least one site is now occupied by an array of gravel pits. Clarence and Florence Hanes, in their 1947 Flora of Kalamazoo County, Michigan: Vascular Plants, noted that C. verna was locally abundant but declining, and that the species had already disappeared from some former haunts. Duane McKenna, in his 2004 revisit of the Kalamazoo County Flora (see Michigan Botanist vol 43, no. 3) described blue-eyed-Mary as "rare" in Kalamazoo County, and stated that it "no longer occurs at several former sites."
My experience over the past 16 years suggests C. verna continues to decline in Michigan, although I lack quantitative data to substantiate these observations. The population at Russ Forest fluctuates year-to-year, and fares best along wide, seasonally wet trails through rich mesic forest dominated by sugar maple (Acer saccharum) and American beech (Fagus grandifolia). In 2010, the species was locally abundant, putting on the best display I had observed since 1996. The situation at Dowagiac Woods is another story. This sanctuary is unique in that its extensive population of Collinsia verna was apparently the impetus for its acquisition and preservation in the 1980s. My first couple visits in the mid-late 1990s were rewarded with acres of low, wet forest carpeted by this species, a remarkable but unfortunately short-lived attraction. By the early 2000s, the population of of blue-eyed-Mary at Dowagiac Woods had declined to a fraction of a percent of its previous numbers. The once aptly-named Blue-eyed Mary Trail, a short loop in the southwestern corner of the forest, is now bereft of its namesake. A few lonely stems appear each year at the margin of the forest along the roadside, reminders of the former spectacle that attracted naturalists and other aesthetes from the surrounding region. Even in the core forest, blue-eyed Mary is now apparently restricted to a few small, local refugia in the floodplain of the St. Joseph River. Numbers have not recovered since the initial decline, and it is unlikely many visitors now or in the future will leave the sanctuary impressed with the displays of blue-eyed-Mary. Theirs is an impoverished sanctuary.
So, why is Collinsia verna declining, and is there anything we can do about it? To some degree, the story of blue-eyed-Mary parallels the stories of many of our other spring flora, which are being battered by a combination of stressors. At Dowagiac Woods, the vicinity of the blue-eyed-Mary trail now exhibits a peculiar lack of leaf litter, and most other wildflower species that were once abundant in the area are now eliminated or reduced to depauperate, often sterile specimens. Deer browse and earthworms, which consume the moist duff that supports so many spring wildflowers, may be culprits here. Invasive plant species, especially garlic mustard, have also increased in this area since the 1990s, likely facilitated by deer and earthworms. Elsewhere in the forest, lush displays of spring wildflowers remain, and it is more difficult to pick up on ecological factors that may be responsible for the decline of C. verna. Maturation of the forest canopy and increased shading, lack of microsite disturbances that prevent or reverse encroachment by aggressive perennials, and a decline in pollinator diversity and numbers, perhaps driven (at least recently) by the application of nicotine-based pesticides (http://en.wikipedia.org/wiki/Imidacloprid_effects_on_bees), may also be factors in the decline of this and other native spring wildflowers. Susan Kalisz and colleagues have found that C. verna seedbanks are short-lived, making the species vulnerable to relatively rapid extirpation if reproductive success is poor and if new colonization events do not occur. This may explain the decline and disappearance of blue-eyed-Mary in small, isolated woodlots, as noted in many former Kalamazoo County sites, and its persistence in larger, more contiguous blocks of habitat such as Russ Forest.
To get 'em while they last, I recommend a few sites open to the public, including the aforementioned Dowagiac Woods and Russ Forest in Cass County, Love Creek Nature Center in Berrien County, and Kalamazoo Nature Center in Kalamazoo County. Floyd Swink apparently collected blue-eyed Mary at Warren Woods State Park in the 1940s, but there are no recent reports. Feel free to report any additional sites for this species in Michigan. Happy botanizing!