Yellow flag Iris (Iris pseudocorus) is an invasive plant. It is a native of Eurasia and was first detected in Washington in 2002.
Yellow iris is widespread in the northeastern United States, where it has been found in the wild for close to 140 years. Iris pseudacorus often grows to such an extent that it is considered invasive and problematic. In its native habitat damage by insects or grazing animals is negligible and in fact, yellow iris is poisonous.