Overview
Nuphar polysepala is an aquatic perennial of ponds, lakes, and slow streams in western North America, growing from a thick fleshy rhizome anchored in bottom mud, with leaves and flowers reaching the surface from water 1-6 feet (0.3-1.8 m) deep. The leaves are large, heart-shaped to oval, 4-16 inches (10-40 cm) long, leathery, and mostly floating, with some held just above the surface. From late spring through summer it produces cup-shaped yellow flowers 2-4 inches (5-10 cm) across, formed mainly of 7-12 thick yellow sepals that enclose small petals and a dense cluster of stamens around a disk-like stigma. The flowers often flush red or green on the outside and rise on stout stalks at or above the water surface. N. polysepala spreads by its branching rhizome to form large colonies in still and slow water, and the rhizome and seeds were used as food by Indigenous peoples. It needs standing water year-round and full sun to bloom, so it cannot grow in seasonally dry sites. Its vigorous spread can cover a small pond, crowding other aquatic plants.
Native Range
Nuphar polysepala is native to western North America, from Alaska and western Canada south through the mountains and lowlands to California, Colorado, and the Pacific Northwest. It grows in ponds, lakes, slow streams, and marshes with standing water.Suggested Uses
N. polysepala is used in natural ponds, large water gardens, and lake and wetland restoration, where its floating leaves shade the water and shelter fish and aquatic life. Its flowers and seeds support pollinators and waterfowl. Its size and spread suit it to large ponds rather than small container water features.How to Identify
Appearance
Size & Dimensions
Height4" - 1'
Width/Spread4' - 8'
Bloom Information
N. polysepala flowers from late spring through summer, roughly May through September depending on elevation. The yellow cup-shaped flowers open by day on stout stalks and draw beetles and flies as pollinators. Rounded fleshy fruits ripen underwater and release seeds that float before sinking.
Detailed Descriptions
Foliage Description
GreenGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight