Photo by Robert W. Freckmann
Aquatic plant of shallow softwater lakes; leaves submerged, very slender and thread-like (0.5 mm), alternate; floating leaves leathery, opposite, narrow (<1 cm), with 3-7 impressed veins.
Status and Rank
- State Status: T
- State Rank: S2
- Global Rank: G4
|County Name||Number of Occurrences||Year Last Observed|
Updated 5/15/2018. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.
Waterthread pondweed is found in seasonally flooded wetlands formed in shallow depressions and potholes in glacial lakeplain and outwash landscapes.
Natural Community Types
For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.
Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.
Robbin's spike-rush, pickerel weed, spatterdock, pipewort, water smartweed, floating bladderwort, Small's spike-rush, bluejoint grass, mermaid weed, and brown-fruited rush.
This species requires protection of habitat and maintenance of hydrology. It is susceptible to excessive recreational use and ORV traffic during low water periods.
General Survey Guidelines
Random meander search covers areas that appear likely to have rare taxa, based on habitat and the judgement of the investigator.
- Meander search
Survey Period: From fourth week of July to fourth week of September
- Elzinga, C.L., D.W. Salzer, and J.W. Willoughby. 1998. Measuring and Monitoring Plant Populations. The Nature Conservancy and Bureau of Land Management, Denver. BLM Technical Reference 1730-1. 477pp.
- Goff, G.F., G.A. Dawson, and J.J. Rochow. 1982. Site examination for Threatened and Endangered plant species. Environmental Management 6(4): 307-316
- Nelson, J.R. 1984. Rare Plant Field Survey Guidelines. In: J.P. Smith and R. York. Inventory of rare and endangered vascular plants of California. 3rd Ed. California Native Plant Society, Berkeley. 174pp.
- Nelson, J.R. 1986. Rare Plant Surveys: Techniques For Impact Assessment. Natural Areas Journal 5(3):18-30.
- Nelson, J.R. 1987. Rare Plant Surveys: Techniques for Impact Assessment. In: Conservation and management of rare and endangered plants. Ed. T.S. Elias. California Native Plant Society, Sacramento. 8pp.
- Crow, G.E. and C.B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. Volume 1. Pteridophytes, Gymnosperms, and Angiosperms: Dicotyledons. University of Wisconsin Press, Madison. 480pp.
- Deam, C. C. 1940. Flora of Indiana. Department of Conservation, Indianapolis. 1236pp.
- Flora of North America Editorial Committee. 2000. Flora of North America, North of Mexico. Volume 22: Magnoliaphyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford University Press, New York. 352pp.
- Gleason, H. A., and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Second edition. The New York Botanical Garden, Bronx. 910pp.
- Gray, A. 1950. Gray's Manual of Botany; eighth ed. Van Nostrand Reinghold, New York. 1632pp.
- Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the vascular plants of Northeastern United States and adjacent Canada. New York Botanical Garden, Bronx. 937pp.
- Voss, E. G. 1972. Michigan Flora. Part I. Gymnosperms and Monocots. Bulletin of the Cranbrook Institute of Science and University of Michigan Herbarium. 488pp.