Working together to strengthen and support noxious weed management efforts in Montana.

Yellowflag Iris

(Iris Pseudacorus)

Common Names

Yellow flag iris, yellow iris, water flag, pale yellow iris, European yellow iris

Description

Yellowflag iris is an aquatic perennial that grows up to 4 feet in height. It likes wetland areas and as it is a beautiful plant.  It was introduced as an ornamental. The leaves resemble cattails; they are sword-shaped, broad, flat and stiff and are a grayish-blue in color. The flower is the distinguishing characteristic with a large, bright yellow, showy flower. Often the flower has brown or purple veins at the base and stems may have multiple flower heads. Flowers bloom from April to June. Seed pods are egg shaped and each of the six pods formed by a fruit capsule produces around 120 seeds.

Habitat

Yellow flag prefers moist soils and full sun.  It grows in fresh or brackish water and often occupies habitats that have low oxygen. It can be found along shorelines, ditches, stream-banks, floodplain forests, areas of shallow water, low-lying wetlands, wet meadows, and fish ponds.

Currently found in the following counties:

Cascade, Flathead, Granite, Lake, Missoula, Powell, Ravalli, Sanders

IWM

Method of Spreading

Yellowflag iris spreads by seeds that float long distances in waterways.  This plant also spreads by its incredibly dense and extensive root system.

Interesting Facts

Yellowflag iris is the only yellow iris found in Montana. Because of its showy nature, this plant has been planted as an ornamental and can still be found online to order. Please be aware of the invasive properties of plants you use to garden or landscape with; if they have been prohibited for planting in other states, please take caution.

Commonly Confused Plants

  • When it is not flowering it may be confused with cattails

Toxicity

It is considered poisonous fpr livestock due to large amounts of glycosides in the leaves and rhizomes,  It is not palatable to livestock, and they will even avoid desirable plants found in dense stands of yellowflag iris. In humans this plant can cause skin irritations or allergic reactions.

Visit our library for additional articles on Yellowflag Iris

Photo credits:Photo Credits: Nancy Loewenstein, Auburn University, www.bugwood.org;Chris Corney, CMC Business Services;Gary Olsen