Lechea tenuifolia var. tenuifolia
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Basis for Listing
Lechea tenuifolia var. tenuifolia has been documented at four locations in Minnesota. One of the four is a historical population in Rice County that is now believed to be extinct. The three remaining sites were found during the course of a recent Minnesota Biological Survey. In all cases, the habitat was high-quality sand prairie or sand savanna. The species is clearly very rare in Minnesota, and its habitat is limited in extent and very fragile. For these reasons, L. tenuifolia var. tenuifolia was listed as a state endangered species in 1996. Maintaining healthy sand prairie and sand savanna habitat requires active management such as prescribed fire to maintain conditions suitable for L. tenuifolia var. tenuifolia. Potentially conflicting land uses and increasing pressure for residential development may make such land management difficult. With these threats and so few populations, the species' survival in Minnesota is tenuous.
Foliage of L. tenuifolia var. tenuifolia is green, with soft, short, downy hairs on the underside of the leaves, on the midrib and the margins. The flowers of species in the genus Lechea are very numerous, minute, red, and in a leafy cluster. Flowers have 3 petals that are shorter than the 5 sepals. Lechea tenuifolia var. tenuifolia has 2 outer sepals that are as long as or longer than the 3 inner sepals. The other 2 Minnesota species of Lechea, L. intermedia (intermediate pinweed) and L. stricta (prairie pinweed), have 2 outer sepals that are noticeably shorter than the 3 inner sepals. Like the other two Lechea species, typical plants of L. tenuifolia var. tenuifolia are 10-25 cm (4-10 in.) tall (Great Plains Flora Association 1986; Gleason and Cronquist 1991).
In Minnesota L. tenuifolia var. tenuifolia inhabits dry, sandy prairies or openings in sand savannas. In neighboring states it is found in similar habitats such as sandstone outcrops, sandy slopes, and open, sandy woods. Associated species include Cyperus lupulinus (slender nut sedge), Koeleria macrantha (Junegrass), and Solidago nemoralis (gray goldenrod).
Biology / Life History
It is a rare event for the tiny flowers of L. tenuifolia var. tenuifolia to open, but it is alleged that they will open in the early morning light of bright days. Each fruit has 2-5 seeds. Sterile shoots develop at the base of plants late in the season (Great Plains Flora Association 1986; Gleason and Cronquist 1991).
Conservation / Management
The type of dry, sandy prairies that contain L. tenuifolia var. tenuifolia are often threatened by agricultural conversion, shrub and tree encroachment, noxious weed invasion, and residential development. Although L. tenuifolia var. tenuifolia habitats may not be prime for housing development, the increasing demand for real estate has resulted in the development of relatively marginal sites in recent years, and the trend seems to be continuing. One of the L. tenuifolia var. tenuifolia sites found in recent years is on an abandoned railroad right-of-way, which have been coming under significant development and agricultural pressure in recent decades. It is essential that prairie remnants, including those in railroad rights-of-ways be protected.
Conservation Efforts in Minnesota
The Dakota and Fillmore county populations of L. tenuifolia var. tenuifolia exist on public land, offering good prospects for long-term conservation of this species and its habitat. One population is on a Wildlife Management Area and the other is on a Scientific and Natural Area.
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.
Great Plains Flora Association. 1986. Flora of the Great Plains. University Press of Kansas, Lawrence, Kansas. 1,402 pp.