Rare Species Guide

  Basis for Listing

Crataegus douglasii (black hawthorn) has two distinct and widely disjunct ranges. Its main range is centered in the Cordillera region of the Pacific Northwest, where it may be locally common. It has a smaller secondary range in the Upper Great Lakes region, where it is generally rare or at least less-widely distributed. This secondary range actually consists of several small discontinuous populations or population centers restricted to the immediate vicinity of Lake Superior and Lake Huron. The climatic influence of the lakes presumably provides an important component of this species’ habitat. In Minnesota, C. douglasii has been found only near Lake Superior in Lake and Cook counties (North Shore Highlands Subsection).

When C. douglasii was listed as a threatened species in 1996, it was known from only a handful of locations, and the populations were quite small. Since that time, it has been found at several more locations, and we have a better understanding of its habitat requirements and population trends. For these reasons, in 2013 its status was downgraded from threatened to special concern.

  Description

Crataegus douglasii is a tall shrub or small shrub-like tree, with 1-5 or more upright stems growing to a height of 7.7 m (25 ft.) and a diameter of 25 cm (10 in.). Compound thorns are absent, but simple thorns are usually abundant and 1.5-3.0 cm (0.6-1.2 in.) long. Mature leaf blades are obovate to elliptic, 4-7 cm (1.6-2.8 in.) long, and 2.5-5.0 cm (1-2 in.) wide; the base is acutely or occasionally obtusely angled; the lower surface has tufts of relatively long straight or wavy hairs in the axils of the lower lateral veins, otherwise glabrous. Inflorescences are glabrous, with 5-18 flowers each; flowers are white; sepals are glandular-serrate; stamens, 5-10; anthers pale pink to nearly white. Fruits are black to purple-black pomes, 11-15 mm (0.4-0.6 in.) long, and 9-13 mm (0.4-0.5 in) wide (Smith 2008). 

Its closest look-alike, and the only other hawthorn to regularly occur with it, is C. chrysocarpa (fireberry hawthorn). Crataegus douglasii differs from it, and from all other Minnesota hawthorns, by the shortness of its thorns and the black color of its fruit.

  Habitat

All known populations of C. douglasii in Minnesota are found within about ten miles of Lake Superior (North Shore Highlands Subsection) in a narrow band from the Gooseberry River (Lake County) northeastward to the Canadian border at Grand Portage (Cook County), a distance of about 161 km (100 mi.).

Within this narrow band it can be found in a variety of habitat types but primarily in streamside thickets with rocky, gravelly, or clayey substrates. These habitats are often flooded in the spring but rarely experience much sedimentation. Other habitats include bedrock outcrops, brushy meadows, and forest openings.

  Biology / Life History

The flowers of C. douglasii are effectively pollinated by a number of flying insect species, though bees are likely the most important class of pollinator. The fruits are eaten by a variety of animals, such as insect larvae, rodents, bear, deer, and especially birds (Martin et al. 1951), which are likely the primary agent for long-range dispersal. The seeds usually take 2 years to germinate. Once established in a favorable habitat, C. douglasii is notably slow-growing, taking several years to reach maturity. Once mature, they normally flower annually and often produce abundant fruit. Older individuals are often surrounded by a younger generation, produced by seeds falling directly from the parent tree and possibly by root suckering. The role of suckering in hawthorn ecology is unclear, but observations of C. douglasii in Minnesota would indicate that they do not sucker or that they sucker weakly or infrequently (Smith 2008).

Although habitats of C. douglasii have a relatively low risk of fire, they are still exposed to periodic natural disturbances, such as erosion, windthrows, and insect outbreaks. In general, C. douglasii appears rather mobile and well-adapted to habitat disturbances. It seems to tolerate competition from similar size shrubs but needs a fair amount of sunlight from above and apparently does not reproduce in a closed-canopy forest. It is tenacious and relatively long-lived, with credible evidence of larger individuals being 60-70 years old, with 80 to 90 years possible (Smith 2008).

  Conservation / Management

Crataegus douglasii inhabits a complex landscape and is regularly subjected to a wide variety of ecosystem perturbations, such as stream flooding, beaver activity, blowdowns, insects, disease, fire, and ice-scouring. The best, and possibly only way to conserve this species in its natural habitat is to maintain its ecosystem and all the natural disturbances associated with it.

  Best Time to Search

With experience, it is possible to identify C. douglasii by the shape of the leaves and the shortness of the thorns. Without experience, searches should be conducted when plants are in flower, from about June 12 to June 25, or when in fruit, from about August 20 to Sept 10.

  Conservation Efforts in Minnesota

The Minnesota Biological Survey has been completed in most of the anticipated range of this species in the state.  A number of C. douglasii populations occur in state parks, offering opportunities to conserve this species on public land.

  Authors/Revisions

Welby Smith (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

Coffin, B., and L. Pfannmuller, editors. 1988. Minnesota's endangered flora and fauna. University of Minnesota Press, Minneapolis. 473 pp.

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.

Judziewicz, E. 1995. Inventory and establishment of monitoring programs for special floristic elements at Isle Royale National Park, Michigan. Unpublished report submitted to the National Park Service, Houghton, Michigan. 772 pp.

Lakela, O. 1965. A flora of northeastern Minnesota. University of Minnesota Press, Minneapolis, Minnesota. 541 pp.

Martin, A. C., H. S. Zim, and A. L. Nelson. 1951. American wildlife and plants: a guide to wildlife food habits. McGraw-Hill, New York, New York. 512 pp.

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, Division of Ecological Resources. 2008. Rare species guide: an online encyclopedia of Minnesota's rare native plants and animals [Web Application]. Minnesota Department of Natural Resources, St. Paul, Minnesota. Accessed 1 July 2009.

Minnesota Department of Natural Resources, Division of Fish and Wildlife. 1995. Statement of need and reasonableness in the matter of proposed amendment of Minnesota Rules, Chapter 6134: endangered and threatened species. Minnesota Department of Natural Resources, St. Paul, Minnesota. 336 pp.

Monson, P. H. 1988. Endangered, Threatened, and Special Concern plants. Grand Portage National Monument, Grand Portage, Minnesota. Olga Lakela Herbarium, University of Minnesota, Duluth. Unpublished report submitted to the National Park Service. 15 pp.

Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis. 320 pp.

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

U.S. Forest Service. 1999. Population viability assessment in forest plan revision. Statement of purpose and reason. Draft species data records: Crataegus douglasii. United States Forest Service, Region 9.

U.S. Forest Service. 2000. Population viability assessment in forest plan revision. Questions for plant population viability assessment panel: Crataegus douglasii. United States Forest Service, Region 9, Duluth, Minnesota.