Piptatherum canadense (Poiret) Dorn
Basis for Listing
Piptatherum canadense (Canadian ricegrass) is a perennial grass that is broadly distributed across forested regions of Canada, New England, and the northern Great Lakes States. In spite of its expansive range, it is not a common species. In fact, it is considered rare in 12 of the 15 states or provinces in which it is known to occur (Lapin 2004). It has also been reported that, in most of its range, populations are relatively small, often with fewer than 100 plants (Lapin 2004).
Perhaps because of the general scarcity of P. canadense, it went undiscovered in Minnesota until 2003. To date, there are less than ten populations known in Minnesota, all are concentrated in the Arrowhead region (Northern Superior Uplands) (Gerdes 2013).
Piptatherum canadense is cespitose and non-rhizomatous. The stems are smooth and 30–90 cm (1-3 ft.) long. The leaves are concentrated at the base of the plant; the leaf blades are 4–15 cm (1.6-6.0 in.) long, 1.0–1.5 mm (0.04-0.06 in.) wide when flat, 0.5–0.8 mm (0.02-0.03 in.) wide when folded or convolute. The inflorescence is a panicle, 9–15 cm (3.5-6.0 in.) wide; the lower nodes of the panicle have 1-2 branches, which are 1–6 cm (0.4-2.4 in.) long. The spikelets consist of 1 floret each and are clustered near the ends of the panicle branches. The glumes of the floret are subequal in length, 3–6 mm (0.12-0.24 in.) long, and 1.3–2.0 mm (0.05-0.08 in.) wide, ovate, 1-3-veined, apices acute to mucronate. The florets are 2.2–4.5 mm (0.09-0.18 in.) long and dorsally compressed; the callus is 0.2–0.5 mm (0.008-0.020 in.) long and is hairy. The lemma of the flower is coriaceous, evenly pubescent; the awn is 5–15 mm (0.2-0.6 in.) long, once- or twice-geniculate. The palea is similar to the lemma in length, texture, and pubescence. The seed is about 2.5 mm (0.1 in.) long and 0.5 mm (0.02 in.) thick (Barkworth 2007).
Piptatherum canadense closely resembles P. pungens (mountain ricegrass), which is a common species in northern Minnesota. Both species are loosely tufted grasses, with narrow leaves; both species grow in dry and nutrient-poor soils, and they may grow together or in close proximity. The two can be easily distinguished by the long awn (6-10 mm vs. less than 2 mm [0.24-0.40 in. vs. 0.08 in.]) and the more open panicle of P. canadense; also, P. canadense is a taller plant.
The Minnesota populations of P. canadense occur primarily on dry and sandy or sandy-gravel soils. Habitat conditions are variable and include the top of a narrow and steep esker, under pine (Pinus spp.), birch (Betula spp.), and aspen (Populus spp.); brushy abandoned logging trails; younger pine plantations; thinned mixed forest of pine and spruce (Picea spp.); and openings and clearings of various sizes (< 0.4- 3.6 ha [<1-9 ac.]). These habitats are all in a fire-prone landscape. However, the major source of habitat disturbance is forestry and forestry-related activities.
Biology / Life History
Piptatherum canadense is a perennial grass that produces wind-pollinated flowers in June and July. The seeds mature and disperse within several weeks of anthesis. Although the act of dispersal has never been studied directly, the seed is equipped with a long awn, which is often thought to catch in the fur or feathers of animals and be carried some distance from the place of origin. Apparently, P. canadense does not possess any structures that would indicate vegetative reproduction (Barkworth 2007), so normal reproduction is probably limited to seeds. Seed dormancy and germination characteristics are unknown. It is possible, perhaps even probable, that P. canadense can lie dormant in a soil seed bank.
Conservation / Management
Management recommendations for P. canadense in Minnesota are difficult to formulate. It is clearly a species of the Laurentian Mixed Forest Province (MNDNR 2003), and it clearly has a complex ecological relationship with forest communities. Yet it appears to survive, perhaps even thrive, in certain heavily managed forest tracts. Under some circumstances, small-scale tree cutting and thinning activities may actually improve conditions for P. canadense, at least in the short term. It appears to reduce competition for sunlight and perhaps enhance the germination of buried seeds (Penskar and Crispin 2009).
Best Time to Search
Searches for P. canadense are best timed to coincide with the maximum development of the inflorescence. This is believed to occur in all of July and the first half of August.
Welby Smith (MNDNR), 2018
(Note: all content ©MNDNR)
References and Additional Information
Barkworth, M. E. 2007. Piptatherum. Pages 144-151 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 24. Oxford University Press, New York, New York.
Gerdes, L. B. 2013. Canada rice-grass. Species new to Minnesota! Minnesota Biological Survey, Minnesota Department of Natural Resources. <https://www.dnr.state.mn.us/eco/mbs/canada_rice_grass.html>. Accessed January, 2013.
Lapin, M. 2004. Piptatherum canadense (Canada ricegrass) conservation and research plan for New England. New England Wild Flower Society, Framingham, Massachusetts.
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.
Penskar, M. R., and S. R. Crispin. 2009. Special plant abstract for Oryzopsis canadensis (Canada rice-grass). Michigan Natural Features Inventory. Lansing, Michigan.
United States Forest Service. 2008. Superior National Forest Rare Plant Guide [web application]. United States Forest Service, Duluth, Minnesota. <http://www.fs.fed.us/r9/forests/superior/documents/SwampBeggar.pdf>. Accessed 10 July 2009.