Have you ever come across a vibrant yellow flower growing near wetlands or marshes? Chances are, you’ve encountered the Yellow Iris, also known as the Yellow flag (Iris pseudacorus). While this perennial plant may appear visually appealing, it poses a severe threat as an invasive species.
A Noteworthy Description
Imagine a robust, sword-like plant with flattened leaves, measuring around ¾ to 1¾ inches wide and up to an impressive 3½ feet long. These leaves fan out gracefully from a thick rhizomatous rootstock. The roots of the Yellow Iris are equally striking, with thick rhizomes and dark sap. But it’s the large yellow flowers that steal the show, boasting three drooping sepals adorned with brown markings. These eye-catching blooms have a diameter of 3 to 4 inches and can occur in clusters of 2 to 10 per stalk. Keep an eye out for these beauty queens from May through July. As for the fruit, it comes in the form of large 1½ to 4-inch capsules, featuring two rows of flat disc-shaped seeds within each of the three chambers.
Origin and Invasion
While native to Europe, Western Asia, and North Africa, the Yellow Iris found its way to the United States as an ornamental plant. Unfortunately, it quickly established itself as a localized and severely invasive species in Maine.
The Tenacious Reproduction
The Yellow Iris employs both rhizome fragments and seeds for reproduction. Even dry rhizomes can remain viable for months, while individual rhizomes can thrive for up to a decade. When it comes to seeds, their longevity is unknown, but approximately 20% of the seeds dispersed in October will germinate the following spring.
Finding Its Habitat
Wetlands are the preferred home for the Yellow Iris, particularly those with nutrient-rich soil. Interestingly, the plant is sometimes intentionally used in remediation efforts to trap sediments and heavy metals. It can be found beside ponds, lakes, and various freshwater, salt, and brackish tidal marshes. In addition, the Yellow Iris can grow in both open wetlands and forested wetlands, thriving under the canopy of trees.
Distinguishing Features
To the untrained eye, the leaves of the Yellow Iris may resemble those of cattails or the native blue flag. However, the Yellow Iris stands apart as the only completely yellow, large wild iris naturalized in North America. Another non-native species, the Siberian iris, has narrower leaves and blue flowers.
Curbing the Invasion: Control Methods
Controlling the spread of the Yellow Iris is not an easy task. Due to the plant containing glycosides, it cannot be grazed by animals. However, a combination of mechanical and chemical treatment can yield positive results. The most widely used method is the application of aquatic-formulated glyphosate. For smaller infestations, a glyphosate solution in a dripless wick applicator can be applied to the folds of the leaves. For larger infestations, foliar applications work best when applied late in the growing season, after flowering is complete, and until just after the first fall frost. It is crucial to follow all label directions and consult the Maine Board of Pesticides Control for specific rules related to herbicide use in or near wetlands and water bodies.
Proceed With Caution
When taking matters into your own hands, be cautious. The Sea to Sky Invasive Species Council in British Columbia has a helpful video demonstration, lasting 1 minute and 42 seconds, showcasing hand pulling as a control technique. However, it’s crucial not to spread rhizome fragments and to contain any parts you pull to prevent their dispersal, especially in moving water systems.
Remember, if you have any questions about invasive species in Maine, feel free to email [email protected]. Let’s work together to preserve the beauty and balance of our natural environments.