Calamagrostis purpurascens R. Br.
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Basis for Listing
Calamagrostis purpurascens (purple reedgrass) is extremely rare in Minnesota. It is known from only four locations, all in the Border Lakes region of northeastern Minnesota. It occurs in crevices and on ledges of tall cliffs. While its rarity was apparent when it was designated special concern in 1996, the lack of data prevented it from being assigned a more protective status. Since that time, however, northeastern Minnesota has been the subject of a comprehensive biological inventory, during which only one of the previously documented populations of C. purpurascens was relocated and no new sites were discovered.
There are relatively few human threats to the species’ habitat. Logging activities or other major disturbance on the land above occupied cliffs could result in increased erosion; and recreational rock climbing, an increasingly popular activity, can dislodge the small vegetation mats growing in rock crevices and on narrow ledges. Given the confirmation of only two populations since 1938, the limited amount of potential habitat in the state, and the potential vulnerability of the extant populations to degradation or destruction, in 2013 the status of C. purpurascens was elevated to endangered.
Calamagrostis purpurascens is a relatively large grass, 30-80 cm (12-31 in.) tall, and it superficially resembles other members of the genus, including the common C. canadensis (Canada bluejoint). The species is a strongly clumped perennial, often with rhizomes 1-4 cm (0.4-1.6 in.) long. The dense, often purple-tinged flower head is 4-13 cm (1.6-5.1 in.) long, with side branches that are held close to the main axis, not spreading. The leaves are 2-5 mm (0.08-0.20 in.) wide, shiny and flat when young but becoming inrolled with age. The leaf edges are rough, and the lower surface is hairy. Distinguishing this species from the other species of Calamagrostis requires an examination of the awn that originates from the lower portion of the back of the lemma. The awn is 4.5-9.0 mm (0.18-0.35 in.) long, twisted at the base, clearly distinct from a tuft of hairs on the floret; and it protrudes from the tip of the spikelet, typically becoming bent at maturity. Because it is twisted at the base, it appears to be attached at an odd angle.
All known occurrences of C. purpurascens in Minnesota are in crevices and on ledges of tall cliffs in the Rove Slate Formation in the Border Lakes region of northeastern Minnesota, specifically along the border between Cook County and Ontario, Canada. Elsewhere in North America, it occurs in arctic, boreal, alpine, and montane habitats, perhaps indicating a broad tolerance for cold, dry conditions and short growing seasons. Plants typically occur in sunny to lightly shaded settings.
Biology / Life History
As with all members of this genus, the flowers of C. purpurascens are wind-pollinated, and the seeds are dispersed by wind, gravity, and possibly animals. In far northern and high altitude parts of North America, this species can be an important part of native grasslands, yet very little is known, specifically, about the biology of this species. Based on observations in Minnesota, it is reasonable to conclude that C. purpurascens possesses specific adaptations for growing in the harsh conditions that prevail on exposed cliffs. Such conditions include desiccation, temperature extremes, increased wind speed, and erosion of the crumbly Rove Slate Formation substrate.
Conservation / Management
Although there are relatively few human threats to the habitat of C. purpurascens, there are still some things that can be done to increase the chances of populations surviving into the future. Logging or other major disturbance on the land above occupied cliffs, could result in increased erosion. Removal of the forest canopy below and adjacent to a cliff also results in increased wind and desiccation. Recreational rock climbing can dislodge the small vegetation mats growing in rock crevices and on narrow ledges. Once the habitats of C. purpurascens have been identified, it is a high priority to control such activities.
Best Time to Search
The best time to search for C. purpurascens is when mature reproductive structures are present, from late June through mid-August.
Conservation Efforts in Minnesota
To date, little if anything has been done to protect the habitat of rare and vulnerable plant species that occur on cliffs. This may be because of the common perception that cliff faces are safe from human activities. While this is true to some extent, there is still a need to closely examine the land use above and adjacent to such habitats.
Welby Smith (MNDNR), 2008 and 2018
Allison, H. 1959. Key to the grasses of Minnesota found in the wild or commonly cultivated as crops. Department of Botany, University of Minnesota, Minneapolis, Minnesota. 52 pp.
Butters, F. K., and E. C. Abbe. 1953. A floristic study of Cook County, northeastern Minnesota. Rhodora 55:21-201.
Coffin, B., and L. Pfannmuller, editors. 1988. Minnesota's endangered flora and fauna. University of Minnesota Press, Minneapolis. 473 pp.
Marr, K. L., R. J. Hedba, and C. W. Green. 2007. Calamagrostis. Pages 706-732 in Flora of North America Editorial Committe, editors. Flora of North America north of Mexico. Volume 24. Oxford University Press, New York, New York.
Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.
Minnesota Department of Natural Resources, Division of Ecological Resources. 2008. Rare species guide: an online encyclopedia of Minnesota's rare native plants and animals [Web Application]. Minnesota Department of Natural Resources, St. Paul, Minnesota. Accessed 1 July 2009.
Minnesota Department of Natural Resources, Division of Fish and Wildlife. 1995. Statement of need and reasonableness in the matter of proposed amendment of Minnesota Rules, Chapter 6134: endangered and threatened species. Minnesota Department of Natural Resources, St. Paul, Minnesota. 336 pp.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.