Bloomipedia
Western yellow pond-lily (Nuphar polysepala)
Photo: Henrik Kibak via iNaturalist · CC BY 4.0 · resized

Flower profile

Western yellow pond-lily

Nuphar polysepala

Western yellow pond-lily (Nuphar polysepala) is a flowering plant in the Nymphaeaceae family, native in the lower 48 states, blooming mostly May–August across the U.S.

Native in the lower 48

Western yellow pond-lily is a wildflower that USDA PLANTS lists as native in the lower 48 states. It's on our flower lists for 2 states, and across the U.S. it's most often seen in bloom in May–August.

12states where USDA records it
2Bloomipedia state lists include it
5,467U.S. sightings*

*iNaturalist research-grade observations, as of October 17, 2026.

On our lists for: Alaska, Wyoming

Quick look

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.

  • It belongs to the Nymphaeaceae family. iNaturalist
  • USDA PLANTS describes it as an herb (forb) with a perennial life cycle. USDA PLANTS
  • USDA PLANTS lists it as native in the lower 48 states and records it in 12 states. USDA PLANTS
  • NatureServe lists it as native to Alaska and Wyoming. NatureServe
  • USDA PLANTS lists its flower color as yellow. USDA PLANTS
  • USDA PLANTS gives its bloom period as spring. USDA PLANTS
  • USDA PLANTS lists a mature height of about 4 ft. USDA PLANTS
  • iNaturalist has 675 research-grade sightings of it in Alaska, ranking #65 among the 121 flowers on our Alaska list. iNaturalist
  • iNaturalist has 395 research-grade sightings of it in Wyoming, ranking #71 among the 113 flowers on our Wyoming list. iNaturalist

When does it bloom?

Flowering records by month across the U.S. (iNaturalist research-grade observations marked “Flowering”) (477 records)
Bloom time in the 2 states whose Bloomipedia list includes it
StateTypePeak bloomSightings*
AlaskaNativefew records (14)675
WyomingNativefew records (24)395

Conservation status

Federal (U.S. ESA)
Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. USFWS ECOS
NatureServe global
T5 See NatureServe for what T5 means. NatureServe
Alaska
No list Alaska has no state law listing endangered or threatened plants, so we show NatureServe's Alaska ranks instead. NatureServe: SNR, not yet ranked in Alaska.
Wyoming
No list Wyoming has no state law listing endangered or threatened plants, so we show NatureServe's Wyoming ranks instead. NatureServe: S3, vulnerable in Wyoming.
Rare elsewhere
Other states where NatureServe ranks it rare or missing: AZ (S1), NV (S1), UT (S2). (S1 critically imperiled, S2 imperiled, SH possibly extirpated, SX presumed extirpated.)

Checked October 17, 2026. Rankings and lists can change, so follow the links for the latest.

Please leave it where it grows

Please don't pick or dig this flower: NatureServe ranks it S3 in Wyoming. NatureServe

Can you eat it?

For peopleNot well documented

None of the sources we checked (NC State Extension (no page for this plant), USDA PLANTS) say whether it's edible or poisonous for people.

For petsNot well documented

It isn't on the ASPCA plant list.

🌿 Never eat a wild plant unless you're certain of its ID; this isn't medical advice. Worried about a person? Call Poison Control at 1-800-222-1222. Worried about a pet? Call your vet.

Where does it grow?

USDA PLANTS records Western yellow pond-lily in 12 states.

recorded by USDA PLANTS on our state lists not recorded

See the full list of states

Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming.

Alaska counties with USDA records: Aleutians West, Anchorage, Bethel, Chugach, Copper River, Denali, Dillingham, Fairbanks North Star, Haines, Juneau, Kenai Peninsula, Kodiak Island, Lake and Peninsula, Matanuska-Susitna, Northwest Arctic, Sitka, Southeast Fairbanks, Yakutat, Yukon-Koyukuk.

Wyoming counties with USDA records: Albany, Big Horn, Carbon, Fremont, Johnson, Park, Sheridan, Sublette, Teton.

Growing conditions

USDA PLANTS gives Western yellow pond-lily a high shade tolerance, low drought tolerance and high moisture use. It is rated for soil pH 5.0 to 8.0 and winter lows down to -62 °F.

Shade tolerance
High
Drought tolerance
Low
Moisture use
High
Soil textures it is adapted to
coarse, medium, fine
Soil pH range
5.0 to 8.0
Minimum temperature tolerated
-62 °F
Frost-free days needed (minimum)
120
Annual precipitation range
10 to 40 inches
Minimum root depth
12 inches
Salinity tolerance
None
Fertility requirement
Medium
Growth rate
Rapid
Lifespan
Short
Active growth period
Spring and Summer
Fruit or seed
Brown · Spring to Fall
Can be propagated by
seed
Commercial availability
Routinely Available

From the USDA PLANTS characteristics data for NULUP. USDA ratings are general guidance for the species, not a guarantee for your garden.

Names, range and relatives

Native status by region (USDA PLANTS): Alaska: Native; Canada: Native; Lower 48 states: Native.

Other scientific names (synonyms in USDA PLANTS): Nymphaea polysepala, Nymphozanthus polysepalus.

County records: USDA PLANTS lists it in 133 counties across 11 states; the most are in Washington (24), California (20), Oregon (20).

Other Nuphar on Bloomipedia (1): Spatterdock.

More from the Nymphaeaceae family (2 on Bloomipedia; most observed first): American white water lily.

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Sources