Hudsonia tomentosa Nutt.
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Hudsonia tomentosa var. intermedia, Hudsonia ericoides ssp. tomentosa
Basis for Listing
Hudsonia tomentosa (beach heather) occurs at several locations in Minnesota; however, all of the populations are very small and restricted to active sand dunes. It seems that every intact, well-developed dune field in the state has a population of H. tomentosa, but it should be noted that sand dunes are very rare in Minnesota, and dunes with active blowouts are rarer still. Furthermore, humans have a destructive tendency to plant pine trees on dunes or use them as recreational areas for off-highway vehicles. Because sand dunes are so rare in Minnesota, they harbor a disproportionate number of rare or highly specialized plant species. This has always attracted the attention of botanists, so it is unlikely that a significant number of sites have gone undiscovered. Given this, the protection of known sites is vitally important to the conservation of this rare species.
Hudsonia tomentosa was listed as special concern in Minnesota in 1996. Subsequent surveys, which are ongoing, have not seen an improvement in state-wide population trends. In fact, threats to existing populations seem to have intensified, primarily from development projects but also from agriculture and invasive species. For this reason, the status of H. tomentosa was elevated to threatened in 2013.
Hudsonia tomentosa is a low, mat-forming, evergreen shrub, usually about ankle high. The flowers are at the ends of short, lateral branches and have bright yellow petals, 3-5 mm (0.1-0.2 in.) long. The fruit is a smooth, brown, ovoid capsule, 2.5-3 mm (0.10-0.12 in.) long. The actual leaves are reduced to tiny, green slivers that turn brown after their first summer and press tightly to the thin, wiry stem. Although H. tomentosa is "evergreen", in the sense that the leaves last through winter, the overall color is more of a pale, gray green, even in summer. The entire plant would be inconspicuous, were it not for its habit of growing in the open, on bare sand (Smith 2008).
In Minnesota, H. tomentosa is sometimes found on high, sandy beaches of large lakes, well beyond the reach of normal wave action; however, most occurrences are on active sand dunes that are not directly associated with lakes. Dunes are rare and local features, yet they can be found at several widely scattered locations across the state. There are a few dunes (Northern Dry Prairie) in the northwestern counties (Prairie Parkland and Tallgrass Aspend Parklands provinces), all of which formed from sand deposited on the shores of Lake Agassiz (a large, extinct glacial lake), and there is an active dune system along Lake Superior, near Duluth (Northern Superior Highlands). There are also dunes on terraces of the Mississippi River (Southern Dry Prairie) that formed from sand deposited by streams of glacial meltwater originating from the Grantsburg sublobe (Paleozoic Plateau). Most dunes in Minnesota, however, are found on the Anoka Sandplain (Cooper 1935) (Southern Dry Prairie), a large outwash plain in the east-central counties that also formed from sand carried by glacial meltwater, only in this case, deposited over a broad, level plain (Wright 1972). In all cases, the sand arrived by water, yet the actual dunes were created by wind and began to form during a particularly warm, dry period about 8,000 years ago (fide Wovcha et al. 1995).
Biology / Life History
Dunes are dynamic habitats, with high crests and bowl-shaped depressions. The depressions are called blowouts and are generally devoid of vegetation except for H. tomentosa and a small group of other rare species such as Aristida tuberculosa (seaside three-awn) and Antennaria parvifolia (small-leaved pussytoes). If these blowouts are not kept open by wind, they become overgrown by grasses and other plants, and H. tomentosa will disappear. On active dunes, H. tomentosa can become nearly buried by blowing sand, but it produces new roots (adventitious roots) along the buried portions of the stem, allowing it to continue to grow upwards.
Conservation / Management
Active, intact dunes require very little, if any, direct management. In most cases they just need to be left alone. Unfortunately, many of the dunes in Minnesota have either been planted to conifers or converted to some form of agricultural use. If trees or shrubs have been planted on the dunes, they need to be carefully removed. Normal foot traffic, if kept to a minimum, may not harm the dunes, though such traffic should be discouraged, and formal footpaths ought to be routed around dunes. Motorized vehicles, on the other hand, can cause severe damage in a very short period of time and must be kept away from dunes. Dune vegetation is just too fragile to sustain any vehicle use, even in the winter.
Best Time to Search
Hudsonia tomentosa is evergreen and can be seen even in winter, if it is not covered by snow. It is perhaps easier to spot during the summer months, when new growth is present.
Conservation Efforts in Minnesota
There are a number of populations of H. tomentosa in state Scientific and Natural Areas, Wildlife Management Areas, and other protected sites. Unfortunately, all of these sites are merely fragments of much larger habitats that have been lost to development of one sort or another.
Welby Smith, MN DNR, 2008 and 2017
Cooper, W. S. 1935. The history of the Upper Mississippi River in Late Wisconsin and postglacial time. University of Minnesota, Minnesota Geological Survey Bulletin 26:84-95.
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 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.
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.
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, 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.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.
Skog, J. T., and N. H. Nickerson. 1973. Variation and speciation in the genus Hudsonia. Annals of the Missouri Botanical Garden 59:454-464.
Smith, W. R. 2008. Trees and shrubs of Minnesota. University of Minnesota Press, Minneapolis. 703 pp.
Wovcha, D. S., B. C. Delaney, and G. E. Nordquist. 1995. Minnesota's St. Croix River Valley and Anoka Sandplain:a guide to native habitats. University of Minnesota Press, Minneapolis. 248 pp.
Wright, H. E., Jr. 1972. Quaternary history of Minnesota. Pages 515-547 in P. K. Sims and G. B. Morey, editors. Geology of Minnesota: A centennial volume. Minnesota Geological Survey, University of Minnesota, St. Paul, Minnesota.