Verbena simplex Lehm.
Basis for Listing
Verbena simplex is primarily found in the eastern continental U.S. and eastern Canada. It is rare at the edges of its range, including in New England, North and South Carolina, Nebraska, Wisconsin, and Minnesota. The species was first collected in Minnesota in 1891 and it has only been observed four times since then. Furthermore, only one of the observations has been made in the last 20 years (1991). While it is possible that a few populations may have been overlooked, it is clear that V. simplex is quite rare in Minnesota. It was listed as a special concern species in 1984.
Verbena simplex is a slender plant that may branch or have single stems. It has spikes of small lavender flowers and square stems. The stems and leaves have minute hairs that are short, sharp, and stiff, and they lie against the leaf or stem surfaces. In Minnesota, the species ranges in height from 30-60 cm (11.8-24.0 in.). One to several stems emerge from the base of the plant and each stem may be simple or branched above. The leaf shape may be linear or narrowly oblong and tapering to a narrow base. The leaves attach almost directly to the stem, with no leaf stalk. Leaf dimensions are typically 3-8 cm (1.2-3.1 in.) long and up to 15 mm (0.59 in.) wide. Leaves are serrate, at least toward their tips.
Verbena simplex seems to prefer open, dry conditions on circumneutral soils (Elliman 2002). The few Minnesota habitats where V. simplex has been observed include thin soil over quartzite bedrock outcrops, a roadside prairie, and a dry hillside adjacent to a road. Throughout its range, V. simplex is found in early successional fields, edges of woods, and rock outcrops (Elliman 2002). In Wisconsin, it has been found in sandy open fields, basalt bedrock glades, and along gravel roads.
Biology / Life History
Verbena simplex is insect pollinated (Moldenke 1958 as cited in Elliman 2002), although specific pollinators are not known. Other species of Verbena are known to be pollinated by bees, wasps, flies, and butterflies (Perkins et al. 1975 as cited in Elliman 2002). Verbena simplex can reproduce without being cross-pollinated with pollen from another individual (Barber 1982). Hybrids within the Verbena genus are common and V. stricta (hoary vervain) in particular can hybridize with each of the other species (Barber 1982).
Conservation / Management
Since there are very few records of this species in Minnesota, it is hard to draw conclusions about appropriate conservation and management practices. We do know that it occurs in open, upland habitats, such as rock outcrops and prairie settings, and that fire is important in the maintenance of these dry, open habitats (Minnesota DNR 2005). It is possible that V. simplex needs some form of disturbance to persist (Elliman 2002), and prescribed fire would provide this by reducing shading from woody species and creating patches of bare ground where seeds could easily germinate.
Best Time to Search
The best time to search for Verbena simplex is when it is flowering or fruiting, from mid-June through September.
Conservation Efforts in Minnesota
The most recently observed Minnesota population occurs on rock outcrops within Blue Mounds State Park. However, no known conservation efforts have been undertaken specifically on behalf of V. simplex at this or other sites.
References and Additional Information
Barber, S. C. 1982. Taxonomic studies in the Verbena stricta complex (Verbenaceae). Systematic Botany 7(4):433-456.
Elliman, T. 2002. Verbena simplex Lehm. (Narrow-Leaved Vervain) conservation and research plan for New England. New England Wild Flower Society, Framingham, Massachusetts.
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.
Moldenke, H. N. 1958. Hybridity in Verbenaceae. American Midland Naturalist 59(2):333-370.
NatureServe. 2010. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia.
Perkins, W. E., J. R. Estes, and R. W. Thorp. 1975. Pollination ecology of interspecific hybridizations in Verbena. Bulletin of the Torrey Botanical Club 102(4):194-198.
Tans, W. E., and H. H. Iltis. 1979. Preliminary reports on the flora of Wisconsin. No. 67: Verbenaceae - the Vervain Family. Transactions of the Wisconsin Academy of Sciences, Arts and Letters 67:78-94.
The Great Plains Flora Association. 1986. Flora of the Great Plains. University Press of Kansas, Lawrence. 1,402 pp.
Wisconsin Botanical Information System (WBIS). 2010. Wisconsin Herbaria Plant Specimen Database. <http://www.botany.wisc.edu/herb/specimenSearch.html>. Accessed 13 March 2010.