Yellow flag-iris is native to Europe and the Mediterranean region, including North Africa and Asia minor. It was introduced into eastern North America in 1911 and into British Columbia in 1931 (Department of Natural Resources and Parks Water and Land Resources, 2009).

Yellow-flag iris is a perennial herb with large showy yellow flowers. They have 3 large downward facing sepals and 3 smaller erect petals. The yellow flowers often have purple/brown veins at the base of the petals. Flowering stalks can produce one to several flowers. The leaves are found at the base of the plant and clasp the stem. A mature plant can range from 1-1.5m tall. At the base of each plant is the root system that forms a dense mat. This mat can be one metre in diameter and extend to 30 centimetres deep (Simon, 2008).

Perennial

The preferred habitats of Yellow-flag iris include freshwater wetlands, fens, ponds, lakeshores, rivers, stream banks, wet pastures, and ditches. These plants tend to grow more proficiently in shallow waters however they can form extensive mats in deep water. This iris species tends to displace natural aquatic and riparian vegetation and reduces critical fish and wildlife habitat. This plant can also cause gastroenteritis in cattle and skin irritation in humans (Simon, 2009).

Yellow-flag iris spreads by seed and roots via water. Because it can reproduce by its roots, an entire infestation can be connected by the same root system. Also, if a piece of root is broken off it is possible for that fragment to form a new plant. Root fragments that dry out can re-establish if they become wet again. (Simon, 2008).

Yellow-flag iris has been classified as a new invader in the Cariboo Chilcotin Coast area. It is thought to occur in the Central Cariboo in the city of Williams Lake near Scout Island.