Stuckenia vaginata (Turcz.) Holub
Coleogeton vaginatus, Potamogeton vaginatus
Basis for Listing
By 1996, Stuckenia vaginata (sheathed pondweed) had been found only five times in Minnesota. For this reason, and because it was known to be rare in adjacent states and throughout much of its total range, it was strongly suspected S. vaginata was rare in Minnesota. However, a systematic inventory of aquatic plants had never been undertaken in the state, so there was much uncertainty. Due to this uncertainty, a status of special concern was conferred in 1996. Subsequent to 1996, the DNR’s Minnesota Biological Survey initiated a thorough survey of the lake flora of Minnesota. By 2015, when 2,025 lakes had been surveyed, S. vaginata had been found in only five of them. This is indicative of a very rare species. Potential threats were identified and included lakeshore development, declining water quality, invasion of non-native species, and artificial water and shoreline manipulation. For these reasons, the status of S. vaginata was up-graded from special concern to endangered in 2013.
Stuckenia vaginata roots in sediments at the bottom of lakes. It produces rhizomes and sometimes tubers, which are the over-wintering structures. The stems are 20-50 cm (8-20 in.) long, and the lower portion is usually branched. The leaves are narrowly filiform to linear, 1-10 cm (0.4-3.9 in.) long, but only 0.2-2.9 mm (0.008-0.114 in.) wide. The leaf apex is rounded and obtuse or slightly notched. The leaves either lack ligules altogether or leaves near the top of the stem may have ligules up to 2 mm (0.08 in.) long. The stipules are inflated to at least twice the width of the stem. The inflorescence is a submerged terminal spike, 1-8 cm (0.4-3.1 in.) long, with 3-12 clusters of flowers. Each fruit is 3.0-3.8 mm (0.12-0.15 in.) long, with an inconspicuous beak.
Given the extreme rarity of S. vaginata in Minnesota, it is difficult to get an accurate profile of its habitat needs. Where found, it has been growing in deepwater zones and near-shore areas of very large fairly alkaline lakes. This is consistent with habitat descriptions provided for populations west of Minnesota, where the species is more common (Hammer and Heseltine 1988).
Biology / Life History
Stuckenia vaginata is a submerged aquatic species that completes its entire life cycle under water. Even flower pollination occurs under water. Seeds are easily carried throughout a lake and between connected lakes by water currents. Dispersal between unconnected lakes is probably accomplished by waterfowl and possibly mammals.
Conservation / Management
Established populations of S. vaginata should have no trouble maintaining themselves, as long as lakes are kept clean, free of exotic species, and free of shoreline and littoral zone manipulation. From the perspective of S. vaginata, a clean lake means a lake free of added plant nutrients that are found in fertilizers and manure, free of herbicides, and free of elevated levels of sediments. Exotic species control can be accomplished by boat inspections. Good shoreline management involves keeping the natural grade and substrate of the shoreline intact, as well as maintaining the natural vegetation. The direct traffic and wave action produced by large watercraft, which can cause aquatic plants to be uprooted, has also been identified as a concern for two of the known S. vaginata populations.
Many resources and tools regarding shoreland management, including lakescaping and shoreland restoration, are available for landowners and land managers, and any opportunity to incorporate these concepts would benefit S. vaginata as well as many other aquatic species.
Best Time to Search
The best time to search for S. vaginata is from early June through the end of July.
Welby Smith (MNDNR), 2008 and 2018
(Note: all content ©MNDNR)
References and Additional Information
Hammer, U. T., and J. M. Heseltine. 1988. Aquatic macrophytes in saline lakes of the Canadian prairies. Hydrobiologia 158:101-116.
Haynes, R. R., and C. B. Hellquist. 2000. Potamogeton. Pages 48-70 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 22. Oxford University Press, New York, New York.
Hellquist, C. B. 1977. Observations on some uncommon vascular aquatic plants in New England. Rhodora 79:445-452.
Les, D. H., and R. R. Haynes. 1996. Coleogeton (Potamogetonaceae), a new genus of Pondweeds. Novon 6(4):389-391.
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. 320 pp.
Pip, E. 1987. The ecology of Potamogeton species in central North America. Hydrobiologia 153:203-216.