Rare Species Guide

  Synonyms

Osmorhiza obtusa

  Basis for Listing

Osmorhiza depauperata is widespread in the western cordillera of North America. It also occurs in northeastern North America; as scattered, disjunct populations across the northern Lake Superior region and Canada; and in southern South America.

Osmorhiza depauperata was first recorded in Minnesota in 1938 from the wilderness of northern Cook County. It occurs primarily in the Border Lakes subsection (Minnesota DNR 2003), but it is also locally concentrated along the Border Lakes and North Shore Highlands subsection ecotone (Minnesota DNR 2009). As of 2008, a total of 21 occurrences had been reported, all within 48 km (30 mi.) of each other in northern Cook County. It is difficult to determine the health of these populations for several reasons. Many of them have never been relocated, at least half of them are known to occur along trails, portages, or areas recently harvested, and none of the populations are being monitored. Given its rarity and restricted range, O. depauperata was listed as a special concern species in Minnesota in 1996.

  Description

Osmorhiza depauperata can be distinguished from the common O. claytonii (Clayton's sweet cicely) and O. longistylis (aniseroot) by the absence of involucels subtending the rays of the umbels. However, distinguishing O. depauperata from the rare O. berteroi (Chilean sweet cicely) is difficult and requires close examination of the mature fruit. In O. depauperata, the fruit is shorter and proportionately wider with a depressed stylopodium that is broader than it is high and with styles about 0.5 mm (0.02 in.) long. In O. berteroi, the body of the fruit is long and narrow with a conical-shaped stylopodium that is higher than it is broad and with styles about 1 mm (0.04 in.) long.

  Habitat

Osmorhiza depauperata most typically occurs in northern mesic hardwood forests, but has also been documented from Fraxinus nigra (black ash) swamps and cliff bases. Other Minnesota locations include openings located within these forested landscapes, drainages, trails, and portages. Soils are often cool and mesic, and comprised of duff over mineral soil or rock. Associated plant species include Betula papyrifera (paper birch), Populus tremuloides (quaking aspen), Abies balsamea (balsam fir), Acer spicatum (mountain maple), Aralia nudicaulis (wild sarsaparilla), Streptopus lanceolatus (rose twistedstalk), and Clintonia borealis (bluebead lily).

  Biology / Life History

Osmorhiza depauperata is a small flowered, short-lived perennial. It flowers in late spring to early summer, and produces fruits armed with antrose (upward directed) bristles that readily attach to clothing, and likely animal fur. Seeds are thus sometimes dispersed in this manner.

The best time to search for O. depauperata is when the plants have mature fruits, likely July to early August. Plants may be discernible mid-June to mid-August, but the presence of mature fruits is necessary to accurately identify the species.

  Conservation / Management

Although several O. depauperata populations have been relocated over the years, population monitoring has not occurred. At the time of their discovery, approximately half of the populations were estimated to have less than a dozen plants while the remaining populations were reported to have between 12-75 individuals. Greater than half of all known populations occur in habitats disturbed by trails, portages, or timber management activities. These populations are thus subject to trail maintenance, additional timber management, and assorted site preparation activities. Canopy removal, herbicide application, discing, and trampling are all potential threats. The spread of invasive plant species, which often accompanies human disturbances, is also a serious concern.

  Conservation Efforts in Minnesota

Approximately half of the known occurrences of O. depauperata in Minnesota are within the Boundary Waters Canoe Area Wilderness and one is within a Scientific and Natural Area. The remaining populations are in other forest lands managed by state, federal, and other ownerships. Well-designed monitoring efforts are necessary in order to better understand species ecology and how populations are responding to management activities and a changing environment. Opportunities currently exist across land ownerships to learn more about the biology and ecology of this species. The Minnesota Biological Survey is in progress in the Border Lakes subsection of northeastern Minnesota and there is good potential for new populations to be recorded.

  References and Additional Information

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. 2009. Ecological Classification System. . Accessed 13 April 2009.

Voss, E. G. 1985. Michigan Flora. Part II: Dicots (Saururaceae-Cornaceae). Cranbrook Institute of Science Bulletin 59 and the University of Michigan Herbarium. University of Michigan, Ann Arbor, Michigan. 727 pp.