Invasive plants pose a significant threat to the environment and can have negative consequences for us as well. Yellow flag iris, though beautiful, is a blooming bully. It crowds out native plants, destroys habitats, and decreases Lake Leelanau's water quality. Controlling these plants helps to preserve our natural heritage. Read on to learn how to identify and remove yellow flag iris from your property.
Meet Yellow Flag Iris
The problem with the perennial yellow flag iris is that it is pretty and a horticultural favorite. The bright yellow flower on the sword like leaf is beautiful in large clumps. According to the US Geological Survey, this Eurasian-native plant arrived in North America in 1871, got to Michigan in 1937, and was first spotted in northern Michigan in 1954. It probably “escaped” from gardens early and now is a thriving invasive.
Yellow flag iris blooms from May to early July and prefers wet areas along shores, roads, and mud. It is easy to identify because it is the only primarily yellow iris (the blue flag iris that blooms later is native). This plant grows between 1 ½ to 3 feet tall, spreading by its abundant seed production and vigorous rhizome growth. This Eurasian invasive plant causes a lot of problems.
The Problems
As the root mass gets bigger, the plant creates a monoculture, hedging out other native species. The fairly large seeds (~1/4”) will drop into the water, float away and be washed up on shore to begin a new plant. The seeds germinate quite easily allowing for its rapid spread. Once established, yellow flag iris can out competes native cattails, sedges, and rushes, reducing habitat for birds, fish, and amphibian species. The aggressive growth habit of rhizomes can have many negative impacts to the structure of riparian environments. Dense stands of yellow flag iris compact soils and increase sedimentation by slowing watercourses, further favoring colonization by the species. All parts of the yellow flag iris plant are poisonous to humans. The plant material contains resins that can cause skin irritation and blistering.
How to Control The Spread
Control of yellow flag iris is difficult. Complete removal of the rhizome system is necessary since any rhizome parts left behind can propagate new stems. Other issues that may hinder hand removal efforts include accidental dispersal by dislodging seeds that float away, water turbidity, transportation of removed plants off site for disposal, and accidental removal of any dormant native tubers, bulbs and seeds in the soil bank.
The yellow flag iris is poisonous to humans. Its resins can cause skin irritation and blistering. Wear protective clothing when removing this plant.
The plant can be dug up, although removal of large infestations can be time consuming and poses risk for recolonization or spread. Follow-up monitoring and maintenance are essential if hand removal is the chosen control option. Plants should be bagged and disposed of in the garbage can. Please remember that protective clothing should be worn while removing yellow flag iris, as it will cause skin irritation. Until you can dig up the plant, remove the flowers immediately after blooming to prevent seed maturation and spreading.
- For plants living in at least 1” of water, continuously cutting off the foliage at ground level repeatedly will result in the plant death within 1 year.
- Continued monitoring of the removal area is necessary, as seeds and pieces of rhizome are likely in the soil.
- There are no approved herbicides for yellow flag iris for use in an aquatic environment, although glyphosate can be used if the plant is located in a dry area.
If you have a mix of yellow flag iris and blue flag iris (native) on your shoreline, mark the yellow flag iris during its bloom time so you know which ones to remove later.
Conclusion
While controlling invasive species can feel like an uphill battle, remember that even small-scale efforts contribute to a larger movement. By staying informed, taking consistent action, and collaborating with your neighbors, you can make a significant difference. Together, we can protect our native ecosystems and ensure a healthier lake for future generations.
Yellow Flag Iris Resources
Blog photos from top to bottom from St. Louis River Alliance, Jon Richfield via Wikimedia Commons, University of Minnesota