Paleyellow (Yellow Flag) Iris

Iris pseudacorus

This species is a native of Europe, and was introduced into the U.S. as an ornamental. It is classified by the Louisiana Department of Wildlife and Fisheries as a Tier I invasive species defined as “currently causing severe or widespread negative impacts on wildlife or natural communities in Louisiana”. Paleyellow Iris has infested wetland habitats in the state including swamps, and the edges of lakes, ponds, and streams. Its ability to withstand droughts and extended anoxic conditions gives this species a competitive advantage over many native wetland plants.

Paleyellow Iris spreads by rhizomes and seeds; both can be readily transported to new locations by floodwaters. This iris forms large clonal colonies that displace native species including native irises; the plant contains glycosides, which are toxic to grazing animals.

It continues to be sold in the nursery trade because Paleyellow Iris is admired for its quick establishment, evergreen foliage, and vigorous growth. This invasive species can be distinguished from native Louisiana Irises by the presence of a central vein in the leaf of the Paleyellow Iris; native Louisiana Irises lack a central vein.

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