Yellow flag iris is a late spring aquatic to semi-aquatic invasive monocot native to Eurasia and Africa that is still sold in nurseries across the country. Almost every state invasive list includes this plant. Easy to grow or transplant, and with showy yellow flowers, this iris is most often found planted in backyard ponds and water features as an ornamental. However, it readily escapes from these areas and spreads into native habitats where it will quickly dominate shallow water areas and become established as a monoculture.
The plant is toxic to herbivores and can cause contact dermatitis if handled without gloves. On the refuge we use an aquatic glyphosate and an aquatic silicone-based surfactant to treat yellow flag iris before it flowers. During flowering if we need to treat, we clip the flowers, create a small reservoir in the stem and fill with just the herbicide. Mechanical removal is also an option for individual plants and small patches but besides the bulb, the plant can also reproduce from rhizomes, so care must be taken to recover all parts and pieces of the plant. Listed as a Class C in Washington State allows for land-fill disposal of the plant, but it still should be bagged before discarding to prevent unintentional spread.
-Keith Rutz, Habitat Restoration Coordinator
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