yellow flag iris, yellow iris, pale-yellow iris
Yellow flag iris is an aquatic perennial in the Iridaceae (iris) family. each stem has several showy yellow flowers, similar to other irises. The leaves are long, flat, sword-like, and grow out of the ground in a fan shape. It produces large seed capsules that are up to 4 inches long. It spreads through rhizomes and seeds that are dispersed by water. It is sometimes planted as an ornamental, and also sometimes for its ability to take up heavy metals.
Height of mature plants
Up to 4 feet tall
April – June
When flowering, yellow flag iris is not easily confused with other plants because it is the only yellow iris that grows in wet areas. However, when not in flower, the leaves may be confused with cattail or broad-fruited bur-reed, although the base has a flat fan shape that helps to identify it.
Yellow flag iris grows in shallow water, often along the shores of ponds, lakes, and slow-moving rivers, as well as in wetlands.
Yellow flag iris spreads rapidly in aquatic habitats, which not only excludes natives plants, but can clog waterways. It is also toxic to humans and livestock. Furthermore, this plant is very expensive and difficult to remove.
Noxious Weed Listing:
- WeedWise: priority
- State of Oregon: Class B
- State of Washington: Class C
- Four County CWMA: Class B
- Columbia Gorge CWMA: Class B
North Africa, Great Britain, Europe, and the Mediterranean