Yellow Flag Iris

Habitat: Yellow flag iris can be found in the emergent plant community and the shoreline and floodplain plant community. It is found in marshes and on the shores of lakes, ponds, and streams; however, they have a high tolerance for drought and can survive long periods in dry, acidic, and low-oxygen soils.

Description: Yellow flag iris can grow up to 0.9-1.2 m in height. The broad, sword-shaped leaves are stiff, erect, and glaucous. They measure between 0.5-1 m long and 1-3 cm wide. The rhizomes are pink-fleshed and 1-4 cm in diameter. The showy flowers bloom from April to June. Most often they are yellow, but their color can also range from nearly white to cream. The flowers are 7-9 cm wide. They are borne on erect peduncles and there are several flowers on each stem. There are six perianth segments that are clawed. Three of these are upward-pointing petals and three are downward spreading sepals (pale-deep yellow, large and petal-like). These sepals often have purple, brown, or red veins on their yellow surface.

Origin and Range: Yellow flag iris originated in Europe, Western Asia, and Northwest Africa. It was introduced to North America in the early 1900s as an ornamental garden flower. It is widespread in North America, being found in nearly every province and state.

Annual Cycle: Yellow flag iris is an herbaceous perennial that reproduces quickly both by seed and vegetatively by pink, freely
branching rhizomes. Yellow flag iris dies back over winter, re-grows in the spring, and flowers late spring/early summer.

Look Alikes: When not flowering, yellow flag iris may be confused with cattail (Typha spp.) and blue flag iris (Iris versicolor). Cattails look similar during spring growth, except that their leaves are arranged in rounded layers rather than flat like the yellow flag iris. Blue flag irises have thinner leaves and blue-purple flowers instead of yellow.

Impacts: The root system of the yellow iris are sturdy and may connect hundreds of flowering plants underground, congesting water flow and leaving no room for native wetland plants to grow. It is also poisonous, harming fish and animals that touch or eat it. CAUTION: The leaves, and especially the rhizomes, of the yellow flag iris contain an irritating resinous substance called irisin. If ingested, irisin can cause severe gastric disturbances. Plants may also cause skin irritations, so caution should be used when trying to remove it.