Appearance

Growth form

This long-lived plant usually stands 1.5–5 ft (0.5–1.5 m) tall and forms dense clumps.

Leaves

Stiff, sword-shaped blue-green leaves have a raised center ridge and can reach about 3 ft (1 m) long.

Flowers

Bright yellow flowers are about 3–4 in (7–10 cm) wide. Three broad outer parts droop while three much smaller inner parts stand up.

Flowering time

In Wisconsin, it blooms from April through June.

Fruit

The fruit is long and six-angled, with flattened brown seeds inside.

Look-alikes

Where it lives

Typical habitats

• pond edges
• marshes
• streams
• wet ditches

Range

Introduced from Eurasia, it is established in many U.S. states, including Wisconsin, where it can escape water gardens into wetlands.

Preferred conditions

It grows in shallow fresh or brackish water and saturated soil, and it can tolerate low-oxygen mud.

Flowering

Flowers Apr–Jun

JFMAMJJASOND

Flowers

Flowers Apr–Jun

Life cycle

Seed dispersal

Corky seeds can float and move along shorelines and waterways.

Growing it

Propagation

Thick branching rhizomes spread outward and can grow into large mats.

Toxicity

Leaves and rhizomes contain irritating compounds. Sap may bother skin, and the plant should not be eaten.

Name and classification

Varieties and forms

Garden forms include pale yellow or white flowers, double flowers, and variegated leaves.

Conservation

IUCN Red List

LCLeast Concern·Low risk of extinction

Threats

Dense stands trap sediment, change wetland conditions, and crowd out native plants. Several U.S. states regulate it as a harmful weed.