Rare Species Guide

  Basis for Listing

Trisetum spicatum (spike trisetum) is a wide-ranging grass found in many parts of the world. In North America, it is found most often in far northern or alpine habitats. Habitats in Minnesota are limited to the shore of Lake Superior (North Shore Highlands Subsection). Searches by botanists have discovered that most of the shoreline is unsuitable for T. spicatum. Only where large level sections of bedrock rise significantly above lake level do suitable conditions develop. 

Only a decade ago, it was assumed that rare plants along the bedrock shoreline of Lake Superior were adequately protected by the remoteness and inaccessibility of their habitat. Since then, the region has experienced a tremendous residential, recreational, and commercial boom. This has raised new concerns about the conservation needs of shore plants. For these reasons, T. spicatum was listed as a species of special concern in 2013. 

  Description

Trisetum spicatum is a clump forming grass that produces both fertile and sterile stems. The stems are usually 10-30 cm (4-12 in.) tall, erect, usually smooth, sometimes hairy. The leaf sheaths are variously pubescent or glabrous; leaf blades are 1-5 mm (0.04-0.07 in.) wide, flat, folded or involute. The inflorescence is a dense spikelike panicle. The spikelets are 5.0-7.5 mm (0.2-0.3 in.) long, with 2(3) florets; upper glumes equaling or exceeding the lowest florets; callus hairs to 1.0 mm (0.04 in.) long; lemmas each with an awn, 3.0-6.0 mm (0.12-0.24 in.) long, emerging from between 2 teeth of the apex; the teeth about 1/3 the length of the lemma; the awns are twisted at their base (Allison 1959; Rumely 2007).

  Habitat

All the Minnesota occurrences of T. spicatum are in full sunlight on exposed bedrock within a short distance of Lake Superior. The bare and smooth rock does not provide habitat, but where crevices or fissures develop in the rock, small amounts of soil will accumulate over time. Eventually these crevices will be colonized by a small number of highly specialized plant species, including T. spicatum.

The habitat is characterized by a cool summer microclimate, low winter temperatures, variable snow depth, high desiccating winds, intermittent wave action, and potentially scouring ice.

  Biology / Life History

Although T. spicatum is clearly terrestrial, there is something about the climate modifying effect of Lake Superior that provides the unique growing conditions required by this species (Randall and Khidir 1986).

The surface of the bedrock outcrops where this species occurs appears nearly devoid of plant life, yet the small crevices where this species actually grows are densely vegetated, and competition in the root zone is intense. It can be imagined that for T. spicatum to become established in such a habitat is a rare event that places a greater importance on persistence.

Laboratory studies have documented vivipary in T. spicatum (Clebsch and Billings 1976). Vivipary is the development of vegetative shoots among the reproductive organs. In effect, T. spicatum uses flowers to produce viable propagules, even if pollination does not occur. This is commonly thought to be an adaptation to harsh environments.

  Conservation / Management

Trampling by people is a concern for the conservation of the small vegetation mats where T. spicatum occurs. There is some evidence that T. spicatum, being a grass, may be better able to withstand foot traffic than non-grass species (Crisfield et al. 2012). Yet it should be noted that these small specialized habitats are home to other rare plant species, such as Allium schoenoprasum (wild chives), endangered; Castilleja septentrionalis (northern paintbrush), endangered; Sagina nodosa ssp. borealis (knotty pearlwort), endangered; and Tofieldia pusilla (small false asphodel), endangered, that are likely more sensitive to disturbance. It seems appropriate to manage these special habitats using the rarest and most sensitive species as indicators. 

Anecdotal reports indicate that the expanding population of Herring Gulls (Larus argentatus) reduces the diversity of native plants along the shore of Lake Superior, especially on the near-shore islands, but the effects upon T. spicatum have never been tested.

  Best Time to Search

For people familiar with grasses, this species is reasonably distinctive and can be identified during most of the growing season. However, the best time to search is when the florets are mature, during July and August.

  Authors/Revisions

Welby Smith (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

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.

Clebsch, E. E. C., and W. D. Billings. 1976. Seed germination and vivipary from a latitudinal series of populations of the arctic-alpine grass Trisetum spicatum. Arctic, Antarctic, and Alpine Research8(3):255-262.

Crisfield, V., S. Macdonald, and A. Gould. 2012. Effects of recreational traffic on alpine plant communities in the northern Canadian Rockies. Arctic, Antarctic, and Alpine Research 44(3):277-287.

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.

NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia.

Randall, J. L., and W. H. Khidir. 1986. Biosystematic studies of North American Trisetum spicatum (Poaceae). Systematic Botany 11(4):567-578.

Rumely, J. H. 2007. Trisetum. Pages 744-753 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 24. Oxford University Press, New York, New York.

Wisconsin Department of Natural Resources. 2007. Narrow False Oats (Trisetum spicatum) factsheet. <http://dnr.wi.gov/topic/endangeredresources/Plants.asp>. Accessed 27 June 2009.