Species Iris, Yellow Flag, Yellow Iris, Water Flag Iris
Iris pseudacorus
Family: | Iridaceae (eye-rid-AY-see-ee) (Info) |
Genus: | Iris (EYE-ris) (Info) |
Species: | pseudacorus (soo-DA-ko-rus) (Info) |
Synonym: | Iris acoriformis |
Synonym: | Iris acoroides |
Synonym: | Iris bastardii |
Synonym: | Iris flava |
Synonym: | Iris lutea |

Class:
Species (SPEC)
Height:
4-6 ft. (1.2-1.8 m)
Spacing:
36-48 in. (90-120 cm)
Hardiness:
USDA Zone 4a: to -34.4 °C (-30 °F)
USDA Zone 4b: to -31.6 °C (-25 °F)
USDA Zone 5a: to -28.8 °C (-20 °F)
USDA Zone 5b: to -26.1 °C (-15 °F)
USDA Zone 6a: to -23.3 °C (-10 °F)
USDA Zone 6b: to -20.5 °C (-5 °F)
USDA Zone 7a: to -17.7 °C (0 °F)
USDA Zone 7b: to -14.9 °C (5 °F)
USDA Zone 8a: to -12.2 °C (10 °F)
USDA Zone 8b: to -9.4 °C (15 °F)
USDA Zone 9a: to -6.6 °C (20 °F)
Sun Exposure:
Full Sun
Sun to Partial Shade
Danger:
Parts of plant are poisonous if ingested
Handling plant may cause skin irritation or allergic reaction
Bloom Color:
Bright Yellow
Bloom Time:
Late Midseason (MLa)
Foliage:
Herbaceous
Smooth
Other details:
May be a noxious weed or invasive
Soil pH requirements:
6.1 to 6.5 (mildly acidic)
6.6 to 7.5 (neutral)
7.6 to 7.8 (mildly alkaline)
Patent Information:
Non-patented
Propagation Methods:
By dividing rhizomes, tubers, corms or bulbs (including offsets)
Seed Collecting:
Allow pods to dry on plant; break open to collect seeds
Awards (if applicable):
Foliage Color:
Bloom Characteristics:
Water Requirements:
Very high moisture needs; suitable for bogs and water gardens
Where to Grow:
Regional
This plant is said to grow outdoors in the following regions:
Auburn, Alabama
Piedmont, Alabama
Tuscaloosa, Alabama
Tuskegee, Alabama
Goodyear, Arizona
Phoenix, Arizona
Cabot, Arkansas
Canoga Park, California
Pittsburg, California
Quartz Hill, California
Sacramento, California
Colorado Springs, Colorado
Harwinton, Connecticut
Bear, Delaware
Deltona, Florida
Old Town, Florida
Sarasota, Florida
Cordele, Georgia
Boise, Idaho
Chillicothe, Illinois
Mapleton, Illinois
Saint Joseph, Illinois
Washington, Illinois
Westchester, Illinois
Indianapolis, Indiana
Nichols, Iowa
Barbourville, Kentucky
Lancaster, Kentucky
Smiths Grove, Kentucky
Abita Springs, Louisiana
Franklin, Louisiana
Pollock, Louisiana
Buckfield, Maine
Pownal, Maine
Brookeville, Maryland
Westminster, Maryland
Nantucket, Massachusetts
Roslindale, Massachusetts
Mason, Michigan
Pinconning, Michigan
Rockford, Michigan
Deer River, Minnesota
Saint Cloud, Minnesota
Madison, Mississippi
Pontotoc, Mississippi
Piedmont, Missouri
Auburn, New Hampshire
Binghamton, New York
Hilton, New York
Port Washington, New York
West Islip, New York
Chapel Hill, North Carolina
Columbia, North Carolina
Elizabeth City, North Carolina
New Bern, North Carolina
Cincinnati, Ohio
Cleveland, Ohio
West Union, Ohio(2 reports)
Hulbert, Oklahoma
Jay, Oklahoma
Muskogee, Oklahoma
Beaverton, Oregon(12 reports)
Lebanon, Oregon
Portland, Oregon(8 reports)
Sutherlin, Oregon
Pittsburgh, Pennsylvania
Conway, South Carolina
Ladys Island, South Carolina
New Ellenton, South Carolina
North Augusta, South Carolina
Prosperity, South Carolina
Wellford, South Carolina
Murfreesboro, Tennessee
Austin, Texas
Boerne, Texas
Corpus Christi, Texas
Fort Worth, Texas
Santa Fe, Texas
Shepherd, Texas
Spring, Texas
Willis, Texas
Ogden, Utah
South Jordan, Utah
Charlottesville, Virginia
Falls Church, Virginia
Locust Dale, Virginia
Roanoke, Virginia
Virginia Beach, Virginia
Brady, Washington
Montesano, Washington
Ocean Shores, Washington
Stanwood, Washington
Eglon, West Virginia
Middleton, Wisconsin
show allGardeners' Notes:
Rating | Content |
---|---|
Positive | On May 27, 2020, Katie_M from Marshfield, MO wrote: So my husband and I moved into our first home a few years ago. The people who lived here before us did not maintain any of the plants or trees. (Shame on them because this little spot is our paradise) We had no idea of all the plants and trees that this land had due to buying in November and they let the grass grow waist high. |
Negative | On Jun 13, 2017, happytomato2008 from Shell Lake, WI wrote: Listed as an invasive species in Wisconsin. On Restricted list. |
Positive | On May 31, 2017, fatboyest from Cabot, AR wrote: Perfect in central Arkansas for a ditch that hardly ever dries out completely (48" precip spread over the whole year); basically a mudhole but now filled with these big self-care plants. |
Positive | On Apr 29, 2015, Kelli from L.A. (Canoga Park), CA (Zone 10a) wrote: I have not had a problem with the plant being invasive, maybe because I am above the recommended zones. It hasn't spread for me at all. |
Negative | On Feb 1, 2014, coriaceous from ROSLINDALE, MA wrote: This escaped into nearby wetland before Massachusetts banned it as destructively invasive. Knowing what I do now, I would never have planted it. |
Neutral | On May 29, 2013, pegster57 from Charlottesville, VA wrote: NEGATIVE: I, like an idiot, put this in a small pond in our deck without checking it out first. It has a root mass from Hell and literally took up every square inch of pond space. It took me and hubby BOTH to lift it up a little so that he could chainsaw it into hunks light enough to lift out. Seriously, keep it away from water. I am surprised there are any bodies of water in existence with this monster around. |
Negative | On Jun 18, 2012, RustyThumb from Ogden, UT (Zone 5b) wrote: This was planted by the previous owner around our fish pond. It was not until this, our third year, that it dawned on me how invasive it has become. I am tearing out huge stands of it because it's dominating and crowding out or hiding other plants I'd like to show off. Now every little start is getting ripped out. It gets down between flag stone and rocks and anchors in so well I have no choice but to just hack away, hoping to do enough damage to kill it. The top of my rock garden is choked with it and I'm going to have to dig in precarious positions to get some of it thinned out. |
Positive | On Jul 14, 2011, Gabrielle from (Zone 5a) wrote: Very prolific with bright, sunny blooms. Blooms in May-June in my garden. |
Positive | On May 29, 2011, relentless1 from La Grange Park, IL wrote: It is a beautiful, floriferous structural plant in my garden. The conditions for keeping it controlled must be wet, heavy clay soil in zone 5 in a flood plain (at least one multi-day flood every year), that dries out and sometimes cracks in the summer. Also good: the deer around here don't eat it! |
Negative | On Feb 20, 2011, dyzzypyxxy from Sarasota, FL (Zone 9b) wrote: This is a non-native invasive species here in Florida. I've just spent an afternoon hacking away at a clump in my small pond. If I wasn't so worried about cutting the liner, I'd use a saw! |
Negative | On Jan 7, 2011, bonehead from Cedarhome, WA (Zone 8b) wrote: I have to give this a negative as well. When we first dug our pond, my aunt gave me some starts. She jokingly told me to just toss them around and not bother to actually plant them. I should have paid attention. These are impossible to get rid of and have taken over huge sections of my pond banks. I actually don't mind them and they are pretty in bloom, but I am concerned about their competition with native plants. The best I can do at this point is to keep them under control and not let them spread any further. |
Neutral | On Jun 19, 2010, genshiro from Whitby, I have had this plant in my pond for several years now. I have found it moderatly invasive in that it will jump up on land and spread if it is not carefully watched and controlled. If controlled, it is a pretty plant and in my area there is really nowhere it can readily escape to. In Ontario, Canada this plant is listed as tollerated, but needing to be monitored and controlled. |
Negative | On Feb 18, 2010, eclayne from East Longmeadow, MA (Zone 5b) wrote: Noxious Weed Information: |
Positive | On Jan 27, 2009, adbjwb from Madison, MS (Zone 8a) wrote: I've been growing Yellow Flag since around 2000. I've planted it in several areas. The rhizomes grow (multiply) each year and can get two or three deep if not thinned every other year, but I've never found plants coming up anywhere other than where I planted them. |
Negative | On May 27, 2008, soivos from Annapolis, MD wrote: Yellow Flag (Iris pseudacorus) is a non-native plant which has escaped cultivation in water gardens and has established itself in local creeks and coves. It spreads rapidly, out-competes our own native species, and is difficult to eradicate. |
Negative | On Mar 15, 2008, distantkin from Saint Cloud, MN (Zone 4b) wrote: The Yellow iris (Iris pseudacorus) is considered an invasive plant by the Minnesota DNR |
Positive | On May 23, 2007, WUVIE from Hulbert, OK (Zone 7a) wrote: I won't give this plant a negative because it is wild by |
Neutral | On Nov 16, 2006, frostweed from Josephine, Arlington, TX (Zone 8a) wrote: Yellow Flag, Iris pseudacorus, is a Naturalized plant to Texas and other States and is considered invasive in Texas. |
Positive | On Apr 16, 2006, Sherlock221 from Lancaster, KY wrote: My experience with this plant has been positive. I bought it at a nursery about 7 years ago. I have it planted in three areas of my yard -- but they are not wet areas. I would call the moisture conditions normal in two areas and a bit on the dry side in one area. They have thrived under both conditions, but have not been invasive. They have spread, but fairly slowly and have lovely blooms that last a long time. Perhaps when grown in a drier area of the garden they are easier to contain. I live in the Bluegrass region of Kentucky. |
Neutral | On Aug 11, 2005, CaptMicha from Brookeville, MD (Zone 7a) wrote: Yellow iris is a very vigorous plant. It blooms in about May here in Maryland, zone 7b. |
Neutral | On Apr 12, 2005, QueenB from Shepherd, TX (Zone 8b) wrote: I didn't realize until I moved to my current location how invasive this stuff can be. There are several locations just within my rural subdivision where this plant has gotten a toe-hold in ditches and along natural run-off areas. It doesn't seem to mind full shade at all, and grows no less than 6 ft. tall in the sun! I made the mistake of planting some in my yard, which I'm more than likely going to pull up before they get out of control. |
Positive | On Jun 22, 2004, trois from Santa Fe, TX (Zone 9b) wrote: This plant should be contained, but is beautiful. It makes a lot of seeds and has spread around the edges of our lily pond.It does not seem to grow in water more than 6 inches deep. It makes a great border/background for a lily pond. We keep a careful eye on it and so far have not seen any unwanted spreading. |
Negative | On May 3, 2004, MTkittlecat wrote: This plant is considered a noxious weed by many states, including Montana (listed 6/03). If I could attach a photo I would show you how it has choked streams and causes channel braiding. Before planting anything please check your state's noxious weed lists. Most are available on-line. Plants are classified as noxious for good reason! You can't trust all nurseries to know what is noxious in your state; especially an on-line nursery that is not familiar with weed lists in all states (I have no particular nursery in mind but have seen a local hardware store carry yellow iris in the spring). Having said that -- I do have yellow iris in a very dry location in my yard (not near any water) and it will spread by tubers, but I have never had it spread by seed. It does not readily take over in... read more |
Negative | On Dec 25, 2003, wnstarr from Puyallup, WA (Zone 5a) wrote: Edgewood, Washington |
Positive | On Nov 24, 2003, suncatcheracres from Old Town, FL wrote: The species may be considered a rampant invasive, but there are some nice hybrid cultivars of this plant that will behave in the garden, although most are no longer pond plants, as they are crossed with "land" irises. 'Holden Clough,' has pretty tan flowers with red veining, and grows to four feet tall. 'Phil Edinger,' has large brassy colored flowers, with heavy brown veining, and also grows to about four feet. 'Roy Davidson,' with dark yellow flowers with finer brown veining, and a maroon signal on the falls, is also smaller. There is a pale cream variety called 'Primrose Monarch,' and a nearly white called 'Alba,' and a solid deep yellow called 'Golden Queen.' The 'Variegata' cultivar has the usual yellow flowers, but in the Spring the foilage is variegated, which fades to all green... read more |
Negative | On Nov 23, 2003, dogbane from New Orleans, LA (Zone 9a) wrote: I have to give this plant a negative because it is so aggressive. It has escaped, and worse released, into areas where it quickly outcompetes native irises, especially I. giganticaerulea because they both thrive under the same conditions. |
Neutral | On May 25, 2003, Terry from Murfreesboro, TN (Zone 7a) wrote: I second Baa's comment about it being unsuitable for smaller ponds. We have a mid-size pond (8x12 or so), and a pot of this (inherited with the pond) has rapidly become grossly overgrown and unwieldy, stretching 4' across, and is now almost too heavy to lift the pot out of the pond. Smaller pots of it were divided (with a machete!) and given away last year; this year may be the year we finally give up on it entirely. |
Neutral | On Aug 5, 2001, Baa wrote: Rhizomatous perennial from Europe, North Africa, Asia Minor and Siberia. |