Species Factsheets

Nuphar microphylla

Yellow Cowlily

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State Status: TU
PBS Status: Pennsylvania Endangered (PE)
Federal Status:

Global Rank: G5T4T5 rank interpretation
State Rank: S1

Nuphar microphylla


Small Yellow Cowlily is an aquatic herb that represents a smaller version of Yellow Cowlily or Spatterdock (Nuphar lutea) that is widespread in Pennsylvania. The Small Yellow Cowlily has its basal part anchored in the substrate of the lake or pond. The leaves arise from this base, via long stalks, and usually are seen floating on the surface of the water. The leaf blades typically have a heart shaped outline, sometimes with a deeply incised base, average about 7.5 cm in width, are untoothed on the edges, and often become purplish below. The yellow flowers, which appear in summer, are located at or slightly above the water surface, and are about 2 cm in width, with a prominent central flat-topped disk where the pollen is deposited. They occur singly on each stalk, which arises from the plant base. The fruit is a spongy or leathery “berry” containing many seeds.

Rank Justification

Critically imperiled in the nation or state because of extreme rarity (often 5 or fewer occurrences) or because of some factor(s) such as very steep declines making it especially vulnerable to extirpation from the state.


The species grows in lakes, ponds and slow-moving sections of rivers and streams.

Survey Dates

Flowers June - September


Small Yellow Cowlily ranges from Nova Scotia to Manitoba and south into New Jersey, Pennsylvania, and Illinois. In Pennsylvania, it represents a northerly species and has been documented historically in the eastern, particularly the northeastern, counties.



The viability of populations of Small Yellow Cowlily and its habitat may be enhanced by creating buffers and protecting the natural hydrology around wetlands, controlling invasive species, and avoiding indiscriminate use of aquatic herbicides.

Conservation Status Map


Map Legend

NatureServe. 2017. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org.

  • NatureServe. 2018. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available at https://www.natureserve.org/explorer
  • Pennsylvania Natural Heritage Program. 2018.
  • Rhoads, A.F. and W.M. Klein, Jr. 1993. The Vascular Flora of Pennsylvania. American Philosophical Society, Philadelphia, Pennsylvania. Rhoads, A.F. and T.A. Block.
  • 2007. The Plants of Pennsylvania: An Illustrated Manual. 2nd edition. University of Pennsylvania Press, Philadelphia, Pennsylvania.
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