Photo by John Ruter, University of Georgia (Image 1605722) [5]
Help remove yellow flag iris from Takoma Park.
The Maryland Department of Agriculture designates yellow flag iris (Iris pseudacorus) as a Tier 1 invasive plant. It poses a serious threat to native plants in wetlands and along streams and rivers in the Chesapeake Bay watershed.
Colonies of this invasive plant can cause sediment to build up, which alters wetlands habitat by creating drier environments.
Local sightings
Even though yellow flag iris is typically found near water, it was seen in three places on a recent walk between Philadelphia and Carroll avenues.
Photos taken between Philadelphia and Carroll Avenues, May 17, 2024.
What to look for
Non-invasive yellow irises exist, so learn to identify yellow flag irises by features other than color alone.
Look for the following characteristics:
- flowers with three downward sepals and three upward petals [4]
- long, narrow capsules with a distinctive shape (see photo) [4]
- erect sword-like leaves, 2-4 feet tall [1]
- flower stems shorter than the leaves [2]
Find many more photos of yellow flag iris on the Maryland Biodiversity Project website.
What to do
If you have yellow flag iris on your property, your best option is to remove the entire plant from root to flower. Dispose of the plant in your garbage. Do not compost it. Find further removal information here. [7]
If you see yellow flag iris on someone else’s property, if possible, ask if they know that the plant is invasive. Share what you have learned from this page.
Alternative native irises
Why not replace invasive and non-native irises alike with our Maryland native irises, such as Northern blue flag (Iris versicolor)?
Photos of Iris versicolor in a streetside native garden on Park Ave.
Iris virginica (southern blue flag iris) is another Maryland native iris alternative to yellow flag iris. [6]
Swamp rose mallow (Hibiscus moscheutos) and blue vervain (Verbena hastata) are other Maryland natives that should do well in the wet conditions that favor yellow flag iris.
Remember: no Maryland native irises are yellow. Native irises and other native plants provide the best habitat for native species.
For more information:
Western Pennsylvania Conservancy
Maryland Biodiversity Project
Maryland Invasive Species Council Invader of the Month
Maryland Department of Agriculture Assessment (basis for Tier 1 classification)
Biology, Ecology, and Management of Yellowflag Iris
Bugwood Wiki
USFA Weed of the Week: Yellow flag iris
Sources:
1. Cornell University Cooperative Extension
2. Common Invasive Plants Easy ID Cards
3. Habitatmatters,org
4. Midwest Invasive Species Information Network
5. Invasive.org
6. North Carolina Extension Gardener Plant Toolbox
7. Invasive Plants in Pennsylvania: Yellow flag iris
Friends of Native Trees in Takoma 