Yellow flag iris is invasive, plus more in this new feature from Erie County Master Gardeners

yellow flag iris
Yellow flag iris. Photo courtesy John M. Randall, The Nature Conservancy,

by Connie Oswald Stofko

You can get lots of well researched information in a new online-publication called WNY Gardening Matters produced by the Cornell Cooperative Extension Master Gardeners in Erie County.

They plan to publish several articles online every month. They’ll let me know when new articles are available, and I’ll share them with you.

Here are the first two:

1. “Invasives: Yellow Flag Iris”

The yellow flag iris (Iris psuedacorus) is pretty, but it can get out of control and create problems along ponds, streams and wetlands. The article describes the flower and tells you what to do to control it.

If you are growing yellow flag iris in your garden, do you have to pull it out because it is an invasive species?

The Master Gardeners sent along this information from Andrea Locke, head of Western New York PRISM (Partnership for Regional Invasive Species Management).

The New York State regulations do not require people to remove yellow flag iris from their gardens.

However, to prevent the spread of an invasive species, Locke suggested removal if the plants are anywhere near a stream, pond or body of water where the seeds could disperse and spread. Also remove the plants if they are near the property edge where seeds could be dispersed off the property through mowing, weeding, etc.

Yellow flag iris contains an irritant, so wearing gloves when removing is recommended.

When removing the plants, put them in a sealed plastic bag and send it out with the trash. Don’t compost the plants because the rhizomes can remain viable for up to three months even without water.

Read the article for more information on the plant itself and how to control yellow flag iris.

2. “Successful Seed Starting for Superior Seedlings”

This article outlines the steps for starting plants from seeds and points out pitfalls to avoid.

15 Comments on “Yellow flag iris is invasive, plus more in this new feature from Erie County Master Gardeners

  1. Bill, ? it’s Rush creek. Tiny, but on the map.
    The biggest concern I have is the seed head problems since the creek feeds into a posted state wetland on the north side of Bussendorfer about the halfway point.
    The plants are showing some signs of growth, while its easy to see the root system grabbing the creek bed.
    It’s interesting and frustrating at the same time.

  2. I just might check that out Vicki I grew up in OP. I’m sure it’s still early to see the affect of the Iris. Which creek are you talking? Luck, muck? It could have been worse!! lol.

  3. Driving around the Alabama- Oakfield marsh area this summer you will see lots of Yelow flag iris.

  4. Bill, I would like to invite you to my creek bed here on the Orchard Park-Hamburg border.
    Or the lakeside invasion in northern Indiana at my mom’s cottage.
    They grow my leaps and bounds, just as Connie describes, and my creekbed is becoming clogged with their roots.
    They cannot be removed other than by digging in the luck since any kind of spray would contaminate the water and fragile ecosystem.
    Please feel free to look me up in the phone book, call me then come take a look.

  5. Please give me 1 example and the location of a large population of this yellow iris and I might have a differing opinion. In my 50+ years I’ve only seen a few and far between sighting of this flower. I’m not trying to start anything, but almost every plant in our gardens come from overseas. I’ve had many store bought aggressives that took years to rid and this iris seems not to have multiplied at all. Maybe it’s the colder climate here that keeps them in check. I enjoy this site and just don’t believe the impact of this Iris without proof. Forgive me for the doubt.

  6. My neighbor had a pretty little yellow flower growing in her lawn. It was so pretty, I almost dug some up to put in my garden. It’s a good thing I didn’t– That plant was lesser celandine, an invasive species that is a problem not only for wild areas, it has proven to be a headache for many gardeners. It’s tough to get rid of! I didn’t know what it was until a reader brought it to my attention. I’m so glad when people ask questions.

  7. Excellent reply Connie. That says it all. Many people just don’t realize how problematic an invasive plant can be.

  8. Bill, thanks so much for your comment. Let’s try to sort this through.

    The article that I linked back to was written by a Master Gardener from Cornell Cooperative Extension. That article noted that yellow flag iris was at one time planted for erosion control and to absorb heavy metals from sewage treatment plant wastewater. There was a time when it was thought this was a good idea.

    You haven’t seen any problems with the plant getting out of control. However, the article says there have indeed been problems where it has escaped cultivation and has formed large, dense colonies along the shores of ponds, lakes and streams as well as in flood plains and in fresh or brackish marshes.

    Iris psuedacorus is now on the list of prohibited plants. This list isn’t created by garden centers; it is created by the New York State Department of Environmental Conservation to control invasive species. Invasive species means a species that is nonnative to a particular ecosystem, and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

    The yellow flag iris was included on the list because of the environmental damage outlined in the article: “Dense mats of yellow iris can reduce the flow and block irrigation systems and flood control ditches. Its seeds can clog pipes and water control structures. Large populations also have the ability to alter an ecosystem. Established roots in a wetland area trap sediment, which promotes growth of more seedlings, which trap more sediment. Enough sediment eventually collects to form a habitat for shrubs or trees, which alters the wetland to a drier ecosystem and reduces the food supply for fish and waterfowl. Dense growth of yellow iris out-competes the growth of native irises as well as native sedges and rushes that are waterfowl habitats.”

    Yellow flag iris are prohibited, not regulated. That means that if you have them growing in your yard, you can continue to grow them. You can find out more about what the terms prohibited and regulated mean on page 2 of the DEC’s Prohibited and Regulated Species document.

    You mention that this plant is free. Yes, it grows widely in our area, but don’t confuse it with being a native plant. It isn’t native to North America. According to the Master Gardener article, it is a native of Eurasia and northern Africa. And it has become an invasive species.

    I have several garden centers and other businesses who sponsor my site. I make no apologies for that. Having sponsors allows me to stay in business. It is how I am able to provide my readers with local gardening information, upcoming events and so much more here on I am not a gardening expert; I am a professional writer. I rely on gardening experts, including those from local garden centers, to provide me with information for my articles.

    However, the article on yellow flag iris wasn’t written by me or by any local garden center. It was written by a Master Gardener from Cornell Cooperative Extension. The article discussed a plant that is listed by the New York State DEC as an invasive species. If you have an objection to the plants that are on the list, you should contact the State DEC directly.

    I hope you find this information helpful.

  9. Never seen more than a couple beautiful yellow flowers scattered along any waters edge. No problem, not invasive just free and that’s a problem for the $$$ retailers!! HMMM!! This site sponsored by Lockwood’s garden center. Coincidence??

  10. The spreading isn’t just the clump in a particular garden.

    The seeds travel on water, by wind and by creatures that eat them. You may not tell that it has spread but it does.

    Any growing on a lake or near water should be removed. The native blue flag iris is an excellent replacement.

  11. Put it in my garden 5 years ago and it hasn’t spread, also have it at my cottage at the waters edge on a small lake. Again in 10 years it hasn’t spread. Either it spreads at a snails pace or this is just a scare tactic!!

  12. Unfortunately its down in the creek of my house. I need help getting rid of it. Physical help. Anyone that can help out?

  13. So the yellow iris is an invasive species! And to think I fretted every spring wondering if it would come back and rejoiced when I planted a rhizome that “took” in another part of the yard. Nevertheless, it’s good to know.

    Also great information in the article, “This Month in the Garden.” Keeps gardening enthusiasm real.

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