Nuphar polysepala, also known as the great yellow pond-lily, wokas, or wocus, is a perennial, rhizomatous, aquatic herb in the genus Nuphar. It has floating green leaves and yellow flowers.
The species is native to wetlands of western North America. The seeds are edible and the plant has been used in traditional medicine to treat superficial irritations.
Description Nuphar polysepala is a perennial,Nuphar polysepala Engelm. (n.d.). Calflora. Retrieved February 2, 2025, from https://www.calflora.org/app/taxon?crn=10994 rhizomatous, aquatic herbNuphar polysepala Engelm. (n.d.). Plants of the World Online. Retrieved February 2, 2025, from https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:1021676-2 with an extensive root system.Klinger, Jesse T. (Jesse Tyler), "The Associations of Epiphytic Macroinvertebrates and Aquatic Macrophytes in Canyon Lake, WA" (2018). WWU Graduate School Collection. 729. https://cedar.wwu.edu/wwuet/729 The rhizomes are up to longMerrick, Samantha; Matthews, Robin A.; and Vandersypen, Joan, "Reed Lake 2013 Aquatic Plant Survey" (2013). Reed Lake. 1. https://cedar.wwu.edu/iws_reed/1 and wide,Nuphar polysepala in Flora of North America @ efloras.org. (n.d.). Retrieved February 2, 2025, from http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500817 spongy, creeping, and branching.DiTomaso, J. M., Healy, E. A. (2003). Aquatic and riparian weeds of the West. p. 110. USA: University of California, Agriculture and Natural Resources. The leaves are submerged or floating.Nuphar lutea ssp. polysepala. (n.d.). Lady Bird Johnson Wildflower Center - the University of Texas at Austin. Retrieved February 2, 2025, from https://www.wildflower.org/plants/result.php?id_plant=NULUP The ovate to oblong leaf is long and wide. The terete petiole is up to long.Nuphar polysepala. (n.d.). Washington Native Plant Society. Retrieved February 2, 2025, from https://www.wnps.org/native-plant-directory/171-nuphar-polysepala
The flowers are solitary, pedunculate, bisexual, and 5–10 cm wide. They float on the water surface or extend beyond it.Wildflowers of the Rocky Mountain Region. (2018). USA: Timber Press. They have (6–)9(–12) green to bright yellow sepals, which occasionally have a red base. The 10–20 green to yellow, thick petals are hidden by the stamens.Nuphar polysepalum Engelm. (n.d.). Alaskaflora. Retrieved February 2, 2025, from http://alaskaflora.org/hulten/do?method=detail&id=450-2 The fruit is ovoid to cylindric, strongly ribbed, 4–6(–9) cm long, and 3.5–6 cm wide. It bears seeds in length.Nuphar polysepala Engelm (Engelm.) E.O. Beal. (n.d.). E-Flora BC: Electronic Atlas of the Flora of British Columbia. Retrieved February 2, 2025, from https://linnet.geog.ubc.ca/Atlas/Atlas.aspx?sciname=Nuphar%20polysepala&noTransfer=0
The chromosome count is 2n = 34.Pellicer, J., Kelly, L. J., Magdalena, C., & Leitch, I. J. (2013). Insights into the dynamics of genome size and chromosome evolution in the early diverging angiosperm lineage Nymphaeales (water lilies). Genome, 56(8), 437-449.
Taxonomy It was published by George Engelmann in 1866.Academy of Science of St. Louis. (1860). Transactions of the Academy of Science of St. Louis (Vol. 2, p. 282). Academy of Science of St. Louis]. https://www.biodiversitylibrary.org/page/5787992Nuphar polysepala Engelm. (n.d.-b). International Plant Names Index. Retrieved February 2, 2025, from https://www.ipni.org/n/1021676-2 The lectotype specimen was collected by C. C. Parry in Osborn's Lake, Colorado, in 1864. It is placed in the section Nuphar sect. Astylus.Nuphar polysepala Engelmann. (n.d.). Database of Vascular Plants of Canada (VASCAN). Retrieved February 2, 2025, from https://data.canadensys.net/vascan/taxon/6714 Etymology The specific epithet polysepala means "with many sepals".Bayton, R. (2020). Practical Uses of Botanical Latin. In The Gardener's Botanical: An Encyclopedia of Latin Plant Names - with More than 5,000 Entries (pp. 22-318). Princeton: Princeton University Press. https://doi.org/10.1515/9780691209135-007
Distribution and habitat It is native to western North America. It is commonly found in shallow muddy ponds from northern Alaska and Yukon southward to central California and northern New Mexico, and can be recognized easily by its large floating leaves and bright yellow blossoms.
It occurs in slowly flowing streams, ponds, and lakes in up to 2,4 m deep water.
Ecology It is pollinated by flies and beetlesWTU Herbarium, Burke Museum, University of Washington. (n.d.). Nuphar polysepala. Burke Herbarium. Retrieved February 2, 2025, from https://burkeherbarium.org/imagecollection/taxon.php?Taxon=Nuphar%20polysepala and provides shelter for fish.
Conservation The NatureServe conservation status is T5 Secure. Uses The seeds are edible; they pop like popcorn, and can be steamed as a vegetable, dried and ground for flour, or can be cooked like oatmeal. Historically they have been a significant source of carbohydrates for the Klamath and Modoc peoples who inhabit the area near Oregon's Upper Klamath Lake.
The leaves and rootstocks have traditionally been used for ulcerous skin conditions and swelling. The rootstock infusion is used as a traditional gargle for mouth, sore throats and douche for vaginal inflammation. One cup of boiling water is used for two tablespoons of chopped rhizome.
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