Rare Species Guide

  Synonyms

Arnica chionopappa, Arnica lonchophylla ssp. chionopappa

  Basis for Listing

Arnica lonchophylla (long-leaved arnica) has strong subarctic affinities and occurs in small isolated populations. Like other far northern species that have disjunct populations in Minnesota, this species seems to persist here because of the climate-modifying effect of Lake Superior and the presence of exposed rocky shores and cliffs. There are only six known locations for A. lonchophylla in Minnesota, and the populations are quite localized. The Arnica plants that occur in Minnesota are the typical variety, and they do not occur elsewhere in the United States but range to the north and east into Canada. The plants called A. lonchophylla that are found in South Dakota, Wyoming, and Montana belong to a different subspecies, ssp. arnoglossa (Greene) Maguire.

The first Minnesota collection of A. lonchophylla was from the cliffs on the south side of Clearwater Lake in Cook County in 1932. It was collected at that site again in 1936 and 1938 by Butters and Abbe (1953), who described it as locally abundant. They were unable to find it elsewhere in Cook County in spite of several years of intensive collecting. This population was finally rediscovered in 1994. Arnica lonchophylla was also found in the 1930s by botanist Olga Lakela on cliffs in what is now Tettegouche State Park. This species was reconfirmed at that location in 2001 and found on a separate cliff area in Tettegouche in 2000.

Two other collections were made in 1941 along the Gooseberry River in what is now Gooseberry Falls State Park. Some of these sites were described as at the upper falls and others at the lower falls. After intensive searching in 1998-2001, it was found at both the lower falls and the uppermost falls. It was also found in 1999 at the mouth of the Manitou River in George Crosby-Manitou State Park. That population is composed of only about 100-150 shoots. Arnica lonchophylla has been listed as a threatened species in Minnesota since 1984. 

  Description

Arnica lonchophylla is a yellow-flowered member of the Aster family, similar to a Packera (ragwort), but distinguished by having opposite leaves. Arnica lonchophylla can be reliably identified in the field with a hand lens. Seeds (achenes) are rimmed with a snowy white pappus. Leaves are opposite and petioled, definitely not clasping, and reduced in size up the flowering stem. Basal leaves are three-nerved and have widely spaced teeth.

  Habitat

In Minnesota, populations of A. lonchophylla occur on mesic cliffs of slate, diabase or basalt bedrock on mossy ledges, or in crevices and cracks. This species was previously thought to occur only in calcareous microhabitats (Gleason and Cronquist 1991). While it is indeed found on calcareous slate, it also occurs on basalt and diabase, which are only weakly calcareous. The presence of mineralized veins or fractures that are calcareous do not seem to be required. The key feature for this subarctic species is that the microhabitat must be consistently cool, shady, and fairly mesic (not too wet or too dry). Such conditions are found on north-facing and west-facing cliffs, most are near the shore of Lake Superior (North Shore Highlands Subsection), while others are as much as 35 km (22 mi.) inland (Border Lakes Subsection).

  Biology / Life History

Arnica lonchophylla is an herbaceous perennial species that persists primarily from rhizomes. Botanical records indicate that in Minnesota populations only a small proportion of the shoots were observed to produce a flowering stem (5-50% flowering). Like similar members of the Aster family, the achenes ripen soon after flowering (late July) and are ready to disperse. Details of the germination, the vegetative longevity of patches, and other aspects of the life history of Minnesota's populations have not been studied.

  Conservation / Management

This subarctic species has a very limited amount of suitable cliff habitat in Minnesota. The currently known A. lonchophylla populations are within the boundaries of managed areas such as State Parks and State Forests, which increases the odds that conservation actions can be taken. Because cliffs are attractive to people, cliff species are sometimes subject to accidental injury such as by rock climbing or off-trail scrambling.

  Best Time to Search

The best time to search for Arnica lonchophylla is when it is in flower from late-June through July. 

  Conservation Efforts in Minnesota

Although the baseline survey of potential habitat has been completed, there remains a rather limited amount of habitat in northern Lake and Cook counties that could potentially harbor this species. Information obtained to date is a great contribution to conservation, giving land managers a sound basis for establishing protection plans.

  Authors/Revisions

Welby R. Smith (MNDNR), 2021

(Note: all content ©MNDNR)

  References and Additional Information

Butters, F. K., and E. C. Abbe. 1953. A floristic study of Cook County, northeastern Minnesota. Rhodora 55:21-55.

Downie, S. R., and K. E. Denford. 1988. Taxonomy of Arnica (Asteraceae) subgenus Arctica. Rhodora 90(863):245-275.

Gleason, H. A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. Second Edition. New York Botanical Garden, Bronx, New York. 910 pp.