Yellow Flag Iris (Iris pseudacorus)



Aquatic perennial growing up to 1.5 m tall.  Large, flat, strap-like green leaves emerge from thickened rhizomes in a distinctive fan shape.  Long stalks end in showy yellow flowers in parts of three. Can be confused with cattails (Typha spp.), but cattail stem bases are round, while iris stem bases are flattened.


Yellow flag iris is native to Europe, western Asia, and north Africa.  On Galiano Island, it is found in creeks and along the margins of lakes and wetlands.


Yellow flag iris can outcompete native wetland vegetation, reducing habitat for many native species.  It can clog waterways, alter hydrology, and make livestock sick if consumed.


To limit population spread, cut, bag, and burn flower heads to prevent seeding.  To remove plants, carefully dig out and remove rhizomes, making sure to reduce fragmentation.  Several passes will be necessary to remove most rhizome fragments.  Seed germination and re-sprouding are to expected post-removal, and can be managed using a heavy rubber mat (such as a pond liner) as a “benthic barrier”.  Apply the mat for at least 70 days to ensure that remaining seedling and fragments are dead.  Removed plant material can be dried out in the sun on an impermeable surface, then discarded in the forest in a shady and dry area, or burned.

Our Experience

Iris is very difficult to remove once established.  Small populations can be managed by removing flower heads annually.  Removal requires repeated digging in the muck to remove rhizomes.  The use of a benthic barrier post-removal will reduce the need for future removal activities.  Iris should be removed from native creeks and wetlands whenever possible, especially when it is upstream of bodies of water.



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