Rare Species Guide

  Basis for Listing

Salix pseudomonticola (false mountain willow) was not known to occur in Minnesota until 1993, when a series of previously misidentified herbarium specimens, collected between 1939 and 1952 along the St. Louis River near Fond du Lac (St. Louis County), were correctly identified by Robert Dorn. Efforts to relocate the Fond du Lac population have been unsuccessful but, in the process, another population was found a short distance away. This newly discovered site is also along the St. Louis River (Carlton County) (North Shore Highlands Subsection), and consists of fewer than ten individuals. Subsequent searches in the northwestern counties (Aspen Parklands Subsection) have discovered a few additional sites. Although habitats in the northwest are not particularly rare, very few of them harbor S. pseudomonticola. The populations in the northwest appear to be continuous with populations in Canada, while the populations along the St. Louis River seem to be anomalous disjuncts. Additional survey work is needed to clarify the species abundance and distribution in the state; however, based on its apparent rarity, S. pseudomonticola was listed as a special concern species in 2013.

  Description

Salix pseudomonticola is a large shrub, with multiple bushy stems, reaching a height of about 3.5 m (11 ft.) in Minnesota. The bark is gray and somewhat rough. The leaves are ovate to elliptical or oblong, 4-11 cm (1.6-4.3 in.) long, and 2.5-6.0 cm (1.0-2.4 in.) wide. The leaf apex is acute to abruptly acuminate, the base is cordate to round, and the margins are serrulate. The stipules are leaf-like, 8-20 mm (0.3-0.8 in.) long. Like the flowers of all willows, those of S. pseudomonticola are borne in unisexual catkins, with each plant bearing either male catkins or female catkins. The catkins appear early in the spring, before the leaves appear. The female catkins are 3-9 cm (1.2-3.5 in.) long and are sessile or borne on flowering branchlets to 0.5 cm (0.2 in.) long. The fruit is a smooth capsule, 4-7 mm (0.2-0.3 in.) long (Dorn 1975; Smith 2008).

When in the field, look for the broad  and finely serrated leaves, large stipules, and strongly red-colored juvenile leaves. Even the mature leaves will usually have a reddish petiole and midvein. The leaves of S. pyrifolia (balsam willow) are similar but lack the prominent stipules, and those of S. eriocephala (heart-leaved willow) are not as broad or as reddish.

  Habitat

In the northwestern counties, S. pseudomonticola occurs in wet brush prairies and shrub swamps, usually in the company of S. discolor (pussy willow), S. bebbiana (Bebb’s willow), and S. eriocephala (heart-leaved willow). The substrate is usually wet mineral soil and shallow peat.

This habitat type is common in that region, and yet S. pseudomonticola appears to be rare or at least uncommon. The habitat along the St. Louis River is more difficult to characterize but appears to be a wet seep on a steep clay bank in a sunny or partially shaded forest opening.

  Biology / Life History

Little is known about the ecology of S. pseudomonticola in Minnesota. Populations in the northwest part of the state have been observed to re-sprout vigorously after fire and after heavy browsing by moose and deer, though being forced to re-sprout for several years in a row is likely deleterious. Sprouts will not produce flowers or seeds for several years. The flowers are pollinated by wind and, to a lesser extent, by flying insects. The seeds are light and have a tuft of long, white hairs that facilitate wind dispersal (Smith 2008). Mature female plants typically produce seeds in abundance, and they do so nearly every year. The seeds germinate quickly upon contact with moist soil but are viable for only a short period of time. Those seeds that do not germinate the first year will not survive into the second year. There appears to be high mortality among seedlings, though actual data are hard to come by.

  Conservation / Management

Most occurrences of S. pseudomonticola are in the northwestern counties, where it appears to be a rare, but established, component of the indigenous “brush prairie” community. As brush prairie has become fragmented by agriculture, the total acreage of this habitat has been reduced to a small percentage of its original extent (Minnesota's Remaining Native Prairie). This has disrupted the normal cycle of wildfire that maintained the character of the community, allowing the brush component to expand to problematic levels. The intervening agricultural areas have exacerbated the problem, by increasing the rate of drainage and introducing exotic species. To the extent possible, it will be necessary to reverse these disruptions, primarily by reinstating a carefully planned fire regime (dormant season fires on a 4-8 year rotation) and protecting or restoring natural drainage patterns.

  Best Time to Search

Salix pseudomonticola can be identified anytime of the year that mature leaves or reproductive structures are present. That will be from mid-May (for flowers) through late September (for leaves).

  Authors/Revisions

Welby Smith (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

Dorn, R. D. 1975. A systematic study of Salix section Cordatae in North America. Canadian Journal of Botany 53(15):1491-1522.

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. 2005. Field guide to the native plant communities of Minnesota: the prairie parkland and tallgrass aspen parklands provinces. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 362 pp.

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

Smith, W. R. 2008. Trees and shrubs of Minnesota. University of Minnesota Press, Minneapolis. 703 pp.