PlantFiles: Yellow Flag
Iris pseudacorus

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.

I was going to try to give some of it away but after reading this they are going in the garbage.

Very prolific with bright, sunny blooms. Blooms in May-June in my garden.

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!

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!

My advice? First check if you are allowed to have it where you live. Next - never! never! plant it in a pond. It will take over. As others have commented, maybe as a garden plant it wouldn't be so aggressive. It does have nice foliage (mine got 6' tall!), pretty flowers (although it doesn't bloom well in my pond) and is an excellent filter plant to keep the pond water clean. But, any iris will do that. Choose a native!

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.

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.

Noxious Weed Information:
Iris pseudacorus L.

This plant is listed by the U.S. federal government or a state.

Connecticut:
yellow iris Invasive, banned
Massachusetts:
Yellow Iris Prohibited
Montana:
yellow flag iris Category 3 noxious weed
New Hampshire:
water-flag Prohibited invasive Species
Oregon:
yellow flag iris "B" designated weed
yellow flag iris Quarantine
Washington:
iris, yellow flag iris Class C noxious weed

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.

Yellow Flag blooms equally where it gets no care at all and right up at the house where it gets watered regularly. I have it planted in full sun in the yard and also on a slope.

This is a great plant for beginners as it will usually bloom the first year planted. It's also great for providing a green screen or backdrop from spring to winter.

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.

Please consider some of the native alternatives instead, such as:
Iris prismatica (slender blueflag)
Iris versicolor (blue flag)
Iris virginica (Virginia blue flag)

For alternatives that are not in the Iris family, refer to the US Fish & Wildlife Service's "Native Plants for Wildlife Habitat and Conservation Landscaping--Chesapeake Bay Watershed"

Orontium aquaticum (Golden Flag) is a wonderful native that offers a longer bloom season of very unique yellow and white 'flowers'

Annapolis, Maryland, Zone 7

The Yellow iris (Iris pseudacorus) is considered an invasive plant by the Minnesota DNR
"Ecological Threat:
* It competes with native shoreland vegetation.
* It is a Eurasian plant that is still sold commercially for use in garden pools.
* Yellow iris is proposed to become a regulated exotic species in Minnesota."

I won't give this plant a negative because it is wild by
nature. It is not a plant you can plunk in the garden and
expect it to keep it's elbows off the table.

As they do quite well in a pond setting, a pot is the only
way to go for those who cannot tolerate it's wild behavior.
You could even bury a pot in the ground, using screen
fabric to ensure the roots don't wander about, then you will
both be happy.

I love my Iris pseudacorus and would like to have even more.
Thank goodness hubby is digging another pond.

Yellow Flag, Iris pseudacorus, is a Naturalized plant to Texas and other States and is considered invasive in Texas.

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.

Yellow iris is a very vigorous plant. It blooms in about May here in Maryland, zone 7b.

I don't really mind it's multiplication because I made sure to plant mine in a dry location that was easy to get to and work on. The long blades lend a nice tropical look and so do the lemon yellow flowers.

I use a good and sturdy garden fork to pry up the bulbs. Then I just wretch them out of the dirt and they pop up individually.

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.

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.

Trois

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 a really dry location and will still bloom.

I specialize in native plant research and restoration and have a lot of botanicals in my yard as well. I feel that anytime you plant a species you can't control because of seed spread or rhizome/suckering there is a chance that plant may become a future noxious weed. Look for a hybrid without nuisance qualities. We have several very pretty noxious weeds in Montana but they will outcompete native vegetation and wildlife food and water sources.

Please know your plant and plant safely!

Edgewood, Washington

If ever there was beauty, but obnoxious hiding behind it, it is this plant. It has choked waterways and taken over much of the waterways of western Washington. Would never suggest you plant it in any wetlands or even in your own private pond. Would rather recommend Japanese iris for your pond or even the Louisiana iris.

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 in the Summer.

The species, on the other hand, can get huge, to over six feet tall, and the rhizomes are the largest of all the irises, and were used medicinally in Europe in the Middle Ages. The species does "best" in or near water, so perhaps planting it in regular, but moist, garden soil will help keep it contained. But it can stand being submerged all year round up to about USDA Zone 4, unlike the more tender Louisiana irises.

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.

I can understand some merits for I. pseudacorus, but they really don't convince me of its worth. The foliage is evergreen (in S. La.) and it flowers over a longer period than do the natives, nonetheless...

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.

The only reason I don't rate it a negative (and haven't already removed it altogether) is because it does provide a place for our fish to spawn.

Rhizomatous perennial from Europe, North Africa, Asia Minor and Siberia.

A large, vigorous plant which spread indefinitely by rhizomes. Has long, grey green, lance shaped leaves which are slightly ribbed. The flowers are beardless and yellow with small black lines and appear on stems which can carry up to 12 flowers at a time.

Flowers May-June

Likes a constantly moist soil or preferably a pond in full sun.

Not suitable for small ponds because of it's sheer size and vigour. However, it happily lives in our pond as long as we keep dividing it every three years or so. When we divide it we need to take a very sharp knife to the roots, there is no way you can just break them apart.

Bees love it and its a great nectar supply in May.