Rare Species Guide

  Synonyms

Scirpus clintonii

  Basis for Listing

In spite of the fact that it is widely distributed in Minnesota, Trichophorum clintonii (Clinton’s bulrush) is very rare here, as well as in adjacent states. The reason for its rarity is not entirely clear. Habitats appear to be very specific, though not easily defined and not easily found on the landscape. They seem to be small and ecotonal in nature, meaning they occur as small inclusions in larger habitat mosaics. Even though there is some uncertainty about the nature of T. clintonii's habitat requirements, habitat trends are clear. Habitats are being lost at both the ecotonal level and the landscape level, especially in the northwestern and southeastern portions of the state (Tallgrass Aspen Parklands and Eastern Broadleaf Forest provinces), and land development is the major cause. Trichophorum clintonii was listed as special concern in Minnesota in 1996. Given that negative habitat trends seem to have continued, the species’ status was elevated to threatened in 2013.

  Description

Trichophorum clintonii has small slender stems that are triangular in cross-section, 10-20 cm (4-8 in.) tall, and they occur in dense clumps. The leaves are less than 1 mm (0.04 in.) wide and are slightly shorter than the stems. Each stem has only 1 spikelet. The spikelet occurs at the top of the stem, though it may appear to be slightly below the top. The achenes are 3-sided and ellipsoidal, 1.5-2.0 mm (0.06-0.08 in.) long, with a rounded base and a barely beaked summit. The perianth bristles are about equal in length to the achene or slightly shorter (Crins 2002).

Trichophorum clintonii looks very similar to T. cespitosum (tufted bulrush). However, stems of T. cespitosum are round in cross-section, and there are virtually no leaf blades; while stems of T. clintonii are triangular in cross-section, and there are at least as many leaf blades as stems. They look very much like the stems except they are flat in cross-section, not triangular.

Superficially, all members of the genus Trichophorum (bulrushes) resemble members of the genus Eleocharis (spike rushes). The difference being that the achenes of Trichophorum lack a clearly differentiated tubercle at the tip (the enlarged persistent base of the style), and the lowest floral scale is somewhat elongated.

Technical Description: Plants perennial. Culms densely cespitose, triangular in cross-section, sharply scabrous on the angles; 8--22 cm (3-9 in.) long at anthesis, ultimately to 35 cm (14 in.) long; 0.2--0.4 mm (0.008-0.02 in.) wide. Rhizomes short or not apparent. Leaves basal or nearly so; lowermost reduced to bladeless sheaths, those above with progressively longer blades, the longest 5--25 cm (2-10 in.) and nearly equaling the culms in length; 0.5--0.8 mm (0.2-0.3 in.) wide. Inflorescence terminal, consisting of a single spikelet. Spikelet 3.5--5.5 cm (1.4-2.2 in.) long, with 3--6 flowers. Involucral bract simulated by an empty scale at the base of the spikelet, this with a short blunt-tipped awn about equaling the spikelet in length. Fertile floral scales yellow-brown to orange-brown; apex obtuse. Perianth bristles 3--6, equaling or slightly exceeding the achene, ± terete, distinctly scabrous. Achenes trigonous, brown, 1.6--1.9 mm (0.6-0.7 in.) long, 0.9--1.1 mm (0.35-0.43 in.) wide, beakless. Maturing early May to mid-June.

  Habitat

In Minnesota, T. clintonii occurs in a variety of habitats, with few obvious features in common. Conditions are usually sunny or partially shaded and range from dry to moist. Soils are often sandy or sandy-loams, though sometimes heavy clay-loams. In the southeast portion of the state, typical habitats of T. clintonii would be considered prairie or savannah communities or sometimes openings or edges in fire-dependent forests of Quercus spp. (oak). Habitats in the northwest portion of the state are in aspen parkland communities, which are also fire-dependent. There is only one record from the northeast portion of the state, and at this time it is unclear how to classify the habitat. It appears to be within a fire-dependent forest system, though details of the micro-habitat that supports the population of T. clintonii are not known.

  Biology / Life History

Among the bulrushes, T. clintonii is notable for being a physically small and ecologically marginal component of its habitat. It is usually found in small and scattered tufts or patches, which appear to be short-lived. On the other hand, populations or metapopulations appear to be stable and long-lived. Flowers are wind-pollinated, and seeds are dispersed by gravity and perhaps small animals.

  Conservation / Management

Management of T. clintonii may require broad thinking. Because most of the recent collections are from habitat fragments in rapidly developing areas of the Twin Cities Metropolitan Area, there is concern that these fragments may not have retained the ecosystem processes necessary to create ideal habitat conditions and assure the perpetuation of the species. Simply protecting the small patches of habitat where this species is found, while ignoring larger landscape dynamics may not be enough. It may be that scattered patches of habitat, though outwardly separate and unconnected, are in fact maintained by the same landscape level processes such as fire or regional groundwater hydrology. In the absence of natural ecological processes, active management in the form of prescribed fire or brush removal may be necessary to control competing vegetation and maintain open habitat conditions. One of the populations in Anoka County was observed to have increased abundance and vigor following a fire in 2000. The spread of invasive species, particularly Phalaris arundinacea (reed canary grass), and Rhamnus cathartica (common buckthorn) also present a serious risk to the long-term viability of the remaining populations.

  Best Time to Search

The best time to search for Trichophorum clintonii is when reproductive structures are present, from early May through the end of June in southern Minnesota, and from late May through June in the northern part of the state.

  Conservation Efforts in Minnesota

Trichophorum clintonii is known to occur in a number of places that are in public ownership and managed for conservation purposes. However, the current status and viability of these populations is unknown.

  References and Additional Information

Crins, W. J. 2002. Trichophorum. Pages 28-31 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.

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. 320 pp.

Smith, W. R. 2018. Sedges and rushes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 696 pp.