Toothcup - Rotala ramosior
State Rank Reason (see State Rank above)
Rare in Montana, where it is known from approximately a half-dozen wetland sites in the valley bottoms in the western portion of the state. Potential threats and impacts to the known occurrences, as well as population trends, need to be evaluated.
Toothcup is a small, glabrous annual with simple or branched, erect to prostrate stems that are up to 10 cm high. The opposite, narrowly lance-shaped leaves have short petioles and are 15-30 mm long. The tiny, solitary flowers are sessile in the axils of upper leaves. The cup-shaped, shallowly 4-lobed calyx is 1-3 mm long in flower but up to 4 mm long in fruit. The 4 stamens are shorter than the 1 mm long, white petals. The fruit is a globose capsule that is ca. 3 mm across.
Flowering in late July-August.
Ammannia robusta has sessile, clasping leaf bases. Members of the genus Gratiola (Plantaginaceae) have short-stalked flowers and separate sepals. A hand lens will be necessary to discern the flower characters.
Throughout U.S. south to S. America (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Open, wet, gravelly soil around ponds and sloughs in the valley zone.
Ecological Systems Associated with this Species
- Literature Cited AboveLegend: View Online Publication
- Hitchcock, C. L., A. Cronquist, M. Ownbey, and J. W. Thompson. 1961. Vascular Plants of the Pacific Northwest, Part 3. Saxifragaceae to Ericaceae. Seattle, WA and London, England: University of Washington. 614 pp.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Additional ReferencesLegend: View Online Publication
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- Cook, C.D.K. 1979. A revision of the genus Rotala (Lythraceae). Boissiera 29:1-?.
- Fassett, N. C. 1985. (3rd ed.) A Manual of Aquatic Plants, with Revision Appendix by E. C. Ogden. University of Wisconsin Press, Madison. 405 pp.