Rare Species Guide

  Synonyms

Rubus deaneanus, Rubus malus, Rubus unanimous, Rubus singulus

  Basis for Listing

In Minnesota, Rubus vermontanus (Vermont bristle-berry) occurs in low numbers at widely scattered locations (Laurentian Mixed Forest). Most habitats, especially those in central Minnesota, are small remnants of original vegetation that may be suffering the effects of ecological isolation and fragmentation. Such effects include increased invasion of non-native species, loss of pollinators, and reduced resilience to ecological perturbations, such as storm damage, drought, and animal grazing.

On the basis of the small number of known populations despite a ten-year statewide survey of blackberries and their habitats, the limited amount of remaining habitat, and potential threats, in 2013 Rubus vermontanus was listed as a species of special concern.

  Description

Rubus vermontanus is a midsize shrub, with bristly biennial stems about 1 m (3 ft.) long. The stems invariably arch, sometimes low to the ground, but they do not tip-root. The leaves of the first-year stems are palmately compound, with 5 or 3 leaflets. The leaflets are noticeably narrow in comparison to the other bristle-berries; even the largest are usually less than 4.5 cm (1.75 in.) wide and are smooth to the touch. Also, the shape is elliptical or even obovate in outline. The inflorescence is a relatively compact raceme, with 5-10 white flowers. The fruit is black, spherical or somewhat conical, 8-13 mm (0.3-0.5 in.) across (Davis et al. 1968; Smith 2008).

  Habitat

In Minnesota, R. vermontanus occurs in partially wooded habitats and woodland edges, particularly where edges constitute ecotones between uplands and lowlands. Shallow wetlands in oak and pine woodlands are excellent habitats, where such habitats exist.

  Biology / Life History

Rubus vermontanus is a fire-adapted shrub that needs direct sunlight and a stable habitat dominated by native plant species. Reproduction is accomplished by both vegetative means (growth from rhizomes) and sexual means. Second-year stems produce relatively large white flowers, designed to be pollinated by a variety of non-specialized flying insects, primarily bees. The seeds are dispersed in the droppings of birds and mammals that eat the fruit.

  Conservation / Management

Maintaining populations of R. vermontanus is dependent on maintaining the integrity of the habitat in which they occur. These days, most habitats are small remnants of larger habitats and are subject to significant edge effect. This is important because, in most cases, invasion of non-native plant species begins at the edge of a habitat, where the soil or vegetation has been disturbed. The smaller the remnant, the greater the proportion of edge habitat to interior habitat. So as a practical matter, small habitats (those less than perhaps 65 ha [160 ac.] need closer monitoring to insure that any problems are caught early. Such a monitoring program must also be alert to problems such as vehicle trespass, trash dumping, and herbicide drift. A program of prescribed fire is needed. Burns ought to be conducted in the early spring, while the plants are still dormant, and should be scheduled no more often than once every 3 - 4 years. The efficacy of the burn plan needs to be reevaluated on a regular basis and must take into account the direct response of R. vermontanus as well as any other rare species occurring there.

  Best Time to Search

Making a positive identification of a suspected R. vermontanus requires there to be fully developed leaves on the primocane and fully developed inflorescences on the floricane, which usually occurs in August. Even though flowers are present earlier in the year (and the plants are highly visible when in flower), identification is difficult because the features needed for identification will not be fully developed at that time.

  Conservation Efforts in Minnesota

Since high-quality woodland habitats have become increasingly rare, several small remnants have been preserved for conservation purposes. A few of these protected habitats have R. vermontanus occurring in them. However, it is not known if these occurrences represent viable populations. It is also unknown how R. vermontanus is responding to existing management regimes.

  Authors/Revisions

Welby Smith (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

Davis, H. A., A. M. Fuller, and T. Davis. 1968. Contributions toward the revision of the Eubati of eastern North America. II. Setosi. Castanea 33(1):50-76.

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. 2006. Tomorrow's habitat for the wild and rare: An action plan for Minnesota wildlife, comprehensive wildlife conservation strategy. Division of Ecological Services, Minnesota Department of Natural Resources. 297 pp. + appendices.

Minnesota Department of Natural Resources. 2009. Map of Minnesota's remaining native prairie 100 years after the public land survey. . Accessed 19 June 2009

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

Widrlechner, M. P. 1998. The genus Rubus L. in Iowa. Castanea 63(4):415-465.