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Yellow Flag Iris

Iris pseudacorus

Description:  Growing to 3 - 5 feet high. The broad, flat leaves are stiff, erect, and green with a grayish-blue cast.  The showy yellow flowers produce a large fruit each filled with over 100 seed. 

Ecological Threat:  Widely planted around the world as a showy garden or pond plant, this iris has escaped intentional plantings. Can form dense colonies and impenetrable thickets in standing water, displacing native species and altering habitat for animals. All parts of the plant are poisonous.

Biology & Spread:  Spreads vegetatively through the break-up of rhizomes and via dispersed seeds. Seeds and fruits are buoyant, allowing them to be dispersed over long distances by water.

Threat in Oklahoma:  Can survive a range of environmental conditions. Can be found in wetlands, shorelines, ditches, stream-banks, floodplain forests, and areas of shallow water.  Currently the largest known infestation is near and along the Blue River in south-central Oklahoma.

Management: Aquatic Weed Management, OSU Extension Factsheet


Additional Information: Problem Horticultural Plants, OSU Extension Factsheet

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