Caltha palustris

Kartesz (1999) recognizes two varieties in North America: var. palustris and var. radicans. Bruce Ford in the Flora of North America (1997) acknowledges that while infraspecific taxa (varieties pubescens and flabellifolia=var radicans) are distinct in their extremes, they represent a morphologic continuum rather than separate taxonomic entities. A complete series of intermediates are present due to environmental plasticity. Schuettplez and Hoot (2004) also note that Caltha palustris displays a considerable amount of morphological variation, as a result of environmental conditions, and do not endorse the recognition of segregates.

Caltha palustris is common and widespread throughout the most of its range.

Caltha palustris is a widespread species with a circumboreal distribution. It is found in Europe, Asia and North America. Its range is strongly associated with moist temperate and cooler climate regions. In North America, the species ranges from the island of Newfoundland and the mid-eastern seaboard states and provinces, through the Great Lakes region and boreal forest regions of Quebec, Ontario, Manitoba, Saskatchewan and Alberta, to the northern areas of Yukon, Northwest Territories, Nunavut and Alaska. Caltha palustris is disjunct in distribution to southern British Columbia, Washington and Oregon.

Caltha palustris is dependent on wet habitats hence it is affected by any landscape alterations involving changes to the water table, or climate variations such as changes to precipitation patterns or temperature. Shoreline development, draining of wetlands, or unrestricted access to streams in pastures for grazers, are some examples of conditions causing declines in populations and reduced vigour of individual plants. One study found the species highly threatened by grazing and sedimentation, and to a lesser extent by forest management practices (Southern Appalachian Species Viability Project 2002).