Rare Species Guide

  Basis for Listing

Dicentra canadensis was probably a more common woodland plant in parts of southeastern Minnesota at the time of settlement, which began in the region around 1850. However, the subsequent loss of habitat as a result of clearing native forests for human activities such as agriculture, industry, road building, and other urban uses has caused the species to become quite rare. This progressive loss of habitat has been ongoing for perhaps 150 years, but likely reached its peak in the late 19th century or early 20th century.

By the 1950s, only small habitat fragments remained and they were often degraded by livestock grazing and timber cutting. As a result, D. canadensis was classified as a special concern species in 1984. Although the threat of habitat conversion remains a concern, a serious new threat has emerged that was unforeseen only a generation ago; the seemingly unstoppable invasion of non-native species into native habitats. The number of invasive species seems to be increasing almost daily, but the ones that most threaten the habitat of D. canadensis are Rhamnus cathartica (common buckthorn), Alliaria petiolata (garlic mustard), and a number of non-native earthworms.

  Description

Dicentra canadensis is a small, woodland wildflower that closely resembles the common and better-known D. cucullaria (Dutchman's-breeches), which invariably occurs in the same habitat. The most obvious difference is the shape of the flower. In D. canadensis, "spurs" at the top of the flower are rounded giving the whole flower an oval or heart shape, while the "spurs" of D. cucullaria are more pointed giving the flower a triangular or arrow-head shape. The leaves and the stalk that bears the flowers arise separately from a cluster of small, globe-shaped, yellow bulblets. The flower stalks may reach 30 cm (12 in.) in height, but are usually shorter. The leaves are compound, meaning they are divided into 4 orders of progressively smaller segments, and they are nearly as long as the flower stalk.

  Habitat

The habitat of D. canadensis in Minnesota is rather consistent and can be broadly described as mesic hardwood forest. There are several types of mesic hardwood forests in the geographic range of the species, but it mostly inhabits the richest types including southern mesic maple-basswood forest and southern wet-mesic hardwood forest (Minnesota Department of Natural Resources 2005). These are rich hardwood forests on loamy soils derived from calcareous till or wind-deposited silt over bedrock on sites that have been historically protected from fires. Most populations of D. canadensis occur on north facing slopes (usually at the base of the slope) or in forested bottomlands of narrow valleys. The canopy trees are most often Acer saccharum (sugar maple), Tilia americana (basswood), and Quercus rubra (northern red oak). Common herbaceous species in this habitat type include Hydrophyllum virginianum var. virginianum (Virginia waterleaf), Sanguinaria canadensis (bloodroot), Uvularia grandiflora (large-flowered bellwort), and Allium tricoccum (wild leek). A shrub layer in this type of habitat is rare or intermittent and includes mostly Carpinus caroliniana ssp. virginiana (blue beech), Staphylea trifolia (bladdernut), and saplings of the dominant tree species (Minnesota Department of Natural Resources 2005).

  Biology / Life History

Dicentra canadensis is considered a spring ephemeral. This means it sends up flowers and leaves very early in the spring, even before the leaves of the canopy trees appear. By the time the canopy leaves are fully grown and the forest floor becomes deeply shaded, the flowers of D. canadensis have been pollinated and the seeds have developed and dispersed. The below-ground bulblets then become dormant and the leaves wither and disappear. The plant does not become active again until fall when the flower buds and leaf primordial are produced below ground. It then becomes dormant again until spring when the process begins again (Stern 1961, 1997). Although D. canadensis spreads primarily by seed, the small bulblets that form underground can, under certain circumstances, become detached from the plant and exposed above ground. They may then be transported (usually downhill by gravity) to another suitable habitat where they may grow into a new plant.

Many other forest plants besides D. canadensis produce flowers in the spring, but most remain photosynthetically active all summer. Even those species that flower in the summer or fall are generally active throughout the growing season. The number of true spring ephemerals in Minnesota is quite small, with fewer than ten known species. The closely related D. cucullaria has a nearly identical life history. Both species are pollinated in the same manner, and by the same bumblebee (Bombus spp.) queens. Yet populations of the two species remain distinct; hybridization is not known to occur (Macior 1978).

The best time to search for D. canadensis is from about the middle of April through the end of May.

  Conservation / Management

The typical forest habitat of D. canadensis is a late successional or climax community that is able to perpetuate itself without major disturbance or intervention. From a management perspective this means the habitat can and, in most cases, should be left alone. Forest management practices that open gaps in the canopy or disturb the soil, and livestock grazing should be avoided. Hunting, maple syrup harvesting, nature study, and other low-impact uses will probably cause no harm as long as motorized vehicles are not used.

One notable exception to this "hands-off" recommendation pertains to ecologically invasive species, particularly such aggressive invaders as Rhamnus cathartica (common buckthorn) and Alliaria petiolata (garlic mustard). Both these species, and others which are appearing on the scene almost daily, are capable of destroying a biotic community in relatively few years. Use of the term "destroy" is not hyperbole; there are all too many examples of intact, full-functioning forest communities turning into ecological wastelands in the wake of relentless invasions of non-native species. Unfortunately, the course of action is not always clear and the amount of labor and money needed to fight the invasion is usually prohibitive.

  Conservation Efforts in Minnesota

Populations of D. canadensis are known to occur at a number of sites that are owned or managed by public land management agencies, primarily the Minnesota Department of Natural Resources. Some of these sites are managed specifically for the perpetuation of healthy forest communities; others are managed for human recreation such as camping, hiking, and hunting, and others for timber production. At this time, there is no coordinated effort to track the effects of these management activities on populations of D. canadensis.

  References and Additional Information

Macior, L. W. 1978. Pollination interactions in sympatric Dicentra species. American Journal of Botany 65(1):57-62.

Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf 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. 394 pp.

Stern, K. R. 1961. Revision of Dicentra (Fumariaceae). Brittonia 13:1-57.

Stern, K. R. 1997. Dicentra. Pages 341-347 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 3. Oxford University Press, New York, New York.