Yellow Iris

Yellow Iris (YI)

Where is YI from and how did it get here?
Yellow iris (also known as yellow flag iris, water flag, or pale yellow iris) is native to Europe, western Asia, and North Africa. It was introduced to North America as an ornamental plant for ponds and water gardens. It was once widely planted in wastewater ponds.

How do I identify YI?
YI is most easily identified when flowering. It is the only yellow-colored iris flower. Each yellow flower has three drooping petals surrounding smaller upright petals. It blooms April-July.
When YI is not flowering, it is very easily mistaken for blue flag iris (native) or cattails. Blue iris tends to be a smaller plant. You can also look at the seed pods. YI pods are 3 sided and angular. If you break the pod open, it has 6 chambers with rows of seeds.
Please contact our Water Program Coordinator if you think you have found YI.

Yellow iris - the only yellow colored iris flower in this region

Yellow iris seed pod

How does YI affect Wisconsin water bodies?
YI forms very dense mats of rhizomes and dead leaves that displace native plant species. YI can also decrease available water in a wetland, turning the wetland into a drier environment, and disrupting water flow. Yellow iris is poisonous to humans and animals if eaten, and its sap can cause skin irritation.

Dense mat of yellow iris

What can be done once YI enters a water body?
Small populations of YI can be manually removed. Be sure to wear gloves and long sleeves, as the sap of the plant may cause skin irritation. All parts of the plants must be removed, especially rhizomes. Cutting flower heads may help prevent the plants from spreading as quickly.
Aquatic herbicides may be effective at removing YI, but a permit would likely be required.

Additional Resources

Manitowish Waters Lakes Association

Wisconsin DNR Aquatic Invasive Species

Citizen Lake Monitoring Network: Get Involved!

Great Lakes Indian Fish & Wildlife Commission (GLIFWC) Invasive Species Area Maps

US Geological Survey Invasive Species Research

Vilas County Land and Water Conservation Department

Invasive Plants Association of Wisconsin



Available for loan.

Lake Plants You Should Know- A Visual Field Guide. University of Wisconsin- Extension.

Aquatic Plants of the Upper Midwest- A Photographic Field Guide To Our Underwater Forests.Written by: Paul Skawinski.

Through the Looking Glass- A Field Guide to Aquatic Plants. Written by: Susan Borman, Robert Korth, and Jo Temte.

Saving Our Lakes and Streams. Written by: James A. Brakken.

Your Help Is Needed

Curly leaf pondweed has been found in the Manitowish Waters Chain. Please keep your eyes open and let us know if you see this aquatic invasive plant along your shorelines or docks. Additionally, please check your boats and props to prevent the spread!

Citizen AIS Lake Monitoring

Join a crew to search for suspicious-looking species (plant or animal). Keep your eyes peeled and report any sightings to us.

Clean Boats Clean Waters

Educate boaters at landings and inspect boats and trailers.

Volunteer today, to protect our waters tomorrow.

Phone: (715) 543-2085

AIS of the Month

September: Mystery Snails

August: Eurasian Water Milfoil

July: Purple Loosestrife

June: Curly Leaf Pondweed