Plant Water Iris Plants

Water irises are semi-aquatic plants often referred to as bog or marginal plants. As a colorful flowering plant, the water iris makes an attractive backdrop for any goldfish pond. When planted in the shallow margins, the foliage keeps pond predators away. Water iris plants are known to be one of the best aquatic plants to remove toxins from the water. Yellow flag irises are often used in the sewage treatment process to assist in removing metals from the water. The larger the root structure, the more toxins that can be taken out of the water.
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Varieties | Grow | Divide | Pests | Buy | → More on Marginals

Water Iris Varieties

There are many iris varieties, all of which have different growing requirements. Only a handful of iris species are considered hydrophilic (water-loving irises); generically called water irises. To avoid confusion the scientific names of water irises include the following.

  • I. pseudacorus. (Yellow flag iris)
  • I. sibirica. (siberian iris)
  • I. Hexagonae (Louisiana iris)
  • I. versicolor (Kermesina iris)
  • I. missouriensis (Rocky Mountain Iris)
  • I. laevigata (Rabbit-ear iris)
  • I. virginica (Southern blue flag)
  • I. ensata (Anytus iris)
  • I. kimballii
  • I. setosa

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Iris Pseudacorus

Grow Water Iris

In the fall, plant water iris plants in pond plant baskets that are wider than they are tall and at a depth of up to 6 inches (15cm). This allows the roots of the water iris to spread out but still be confined to the pond plant basket. Roots not in a pond basket can spread like crazy making it harder to cut them back and potentially puncture a pond liner. In a goldfish pond that doesn’t contain a liner, water irises can be planted completely out of the water in the wet sandy loam banks of the pond. Some species tolerate periods of dryness but typically prefer to have moist to wet soil year around. Place these plants in areas where they receive at least half to full sun. Fertilize regularly throughout the growing and blooming season.

Divide Water Iris

In warmer climates, new growth can begin in November but normally growth begins in the spring. A water iris plant will bloom in the spring and continue to grow into the summer. Warmer summer temperatures will slow the growth and cause some shoots to dieback. The best time to propagate and divide a water iris plant is after flowering in the fall. This occurs at different times and depends on the hardiness zone. In warmer climates, it’s even possible for multiple blooms in the spring and fall. See more on Fall Pond Care.

  • Remove the water iris from the pond plant basket.
  • Wash the root clumps to see the root structure more easily.
  • Separate groups of leaves and pull apart the water iris (a few leaves attached to a small root clump.)
  • Use a knife to cut back most of the roots and leaving only a few inches of roots.
  • Cutback the foliage to about four inches tall.
  • Individually replant the divided plants into pond plant baskets.
  • Water, top with gravel, and place into the margins of the goldfish pond.
Garden Pond with Water Iris

Pond plants can help protect your goldfish from predators

Water irises can also be propagated by the collection of seeds. It’s best to collect water iris seeds right after the flowers have died. They should then be sown immediately. You can sow the seeds in a small plastic container or aquarium that contains a layer of damp heavy loam aquatic potting mix. The water iris seeds should then be covered by the potting mix. Seeds should sprout within three to four weeks of sowing. Established seedlings can be transplanted into larger pond plant baskets.

Water Iris Pests Control

slugs in the garden

Water irises are susceptible to rust, leaf miners, borers, sunscald, cutworms, snails, and slugs and if planted above water, moles. Remove any dead or dying foliage and use a pond safe insecticide to treat most of these. Rust is a fungus that starts in the soil. By removing infected leaves from the soil will help break the cycle. Sunscald happens with the rhizomes are exposed to the sun; add a layer of soil or mulch to protect them. Cutworms can be removed by using a fertilizer fortified with insecticides.

Reviewed By: Tim Winter

Tim Winter has a strong affection for pets and wildlife. His years of experience caring for various types of pets has led him to share his knowledge with others on the best practices in pet care. Tim holds a Bachelor of Science from the University of Oregon School of Journalism and Communications.

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57 thoughts on “Plant Water Iris Plants”

  1. Hi. I’m in Australia and learned the hard way that if you use an algaecide for green algae in your pond, it’ll kill the algae alright, but as it’s dying it pulls all oxygen out of the water. So what you end up with is dead plants and dead fish/tadpoles. Not sure if you have it in the states, but we use small amounts of zeolite, which is a natural mineral to help keep algae at bay.

    • I used a bit of algae killer in my aquarium and had no issues at all… and mine is tropical with bristle nose catfish who eat algae

  2. how deep can I submerge my yellow flag iris in my pond which is 4foot deep. Hopefully to the bottom. Any one know thanks

    • 4ft might be pushing it. They are marginals so typically a few inches to a foot is ideal. Though I’m not 100% certain. you can always sacrifice a few a different depths to see if they grow.

  3. We’ve had 2 garden ponds for 4 years with lots of experimenting on plants and fish. I have crystal clear water always. I started out vacuuming the bottom of the pond every 2weeks. Not good. I read an article saying the way to keep the pond clear is to leave the bottom rocks ind debris alone. The bottom under the pebbles is stinky if you dig it up, just like a farm pond, But, it is full of microbes, these microbes eat the debris, so don’t disturb the bottom. I always have water Lettuce and Water Hyacinth and a small pot of yellow flag iris to eat the nutrients. I clean my small filter box once every 2 weeks. My ponds are only 150 gal. and 50 gal. We have 9 sm. Gold fish in one pond and 4 in the other. My most fun trick is to plant Impatient. I gently wash dirt off roots, place roots in the running water on my waterfall and they bloom their hearts out. Even in the sun.
    Can’t wait until Spring in Kansas.

  4. Hi novice gardener here, I have a very tall iris growing in my small pond. The leaves have become too tall and heavy so the plant is splaying open across the sides of the pond and no longer growing upwards. Is it ok to just cut the leaves right down even thought they are green and healthy? Will they grow back correctly?
    Many thanks

  5. I had mature water iris given to me. A huge massive 3 ft stretch of it and already big sprouts. Now cause it was so heavy and had a developed root system with soil etc. I just threw it in my big pond and let it sink. Do you think this will root on its own and survive? Or does it physically need to be dug and rooted into the bottom of my pond?

  6. I received lots of seeds, some have tiny roots, but some don’t. How do I germinate them?
    Can I plant seeds in wet soil below a spring? I don’t have a pond. Dirt is always wet.

  7. I have just received my iris plants and I need advice on how to plant and keep them healthy through the winter months. My pond is 35’x80’ and natural. I plan to put them in pots to contain them but I’m worried about cold weather. Any advice would be appreciated..

    • Hi full disclaimer, I’m more of an expert on pet care than garden care so take this advice for what it’s worth. Water iris bulbs like some other spring bulbs are pretty hardy. They do well fending for themselves over the winter. Most spring bulbs are recommended to be planted in the fall before the ground freezes. With this winter, that might have not even happened yet. Additionally, water acts as a good buffer and below the surface, the temperatures can be warmer than the outside air temperature. If they were my water irises, I would plant them just as you plan to do and get them in the pond as soon as possible, but again, I’m not an expert on water irises. I recommend calling a reputable pond and garden center to get an opinion from an expert. Or you might try to find an active online forum on garden ponds or pond plants. If you do find your answer, please come back and let us know.

    • I planted my three water iris in a small pond about a month ago and they all seem to have died off. I’m hoping they are adjusting to the new environment. Will they grow back?

      • It’s hard to say. Usually pond plants and other plants in general for that matter, grow in spring, peak in summer and die back in the fall. Something may be off in your pond or how you planted them, perhaps.

  8. II live in St Louis mo …..and have the water iris . It never has bloomed . It is stretching the black plastic pot it is in . If I transplant it will it bloom?

    • Perhaps, but not this growing season. You might also consider how much sun the plant is getting and give it a little bit of fertilizer.

      • Careful with the fertilizer. Some plants, notably morning glories, will produce lush vines but no flowers at all if given even a modest amount of fertilizer. None at all is best for them. Whether this applies to this case with water iris I really don’t know.

    • I use a pruning saw and cut way down into the roots. It is s huge job that i try to stay on top of.
      Had someone else do it the last two seasons and obviously they didn’t go away down and get the roots and now it’s a tangled mess and I’m afraid The fish don’t have much swimming room as I looked there seem many fewer fish this spring !
      My pond is about 4 feet deep and in the past I have also drained about half the water out to make it easier to do this . Good luck!!

      • I would move fish to a separate place then I would go in and remove every one I could find. They will be difficult to completely eradicate, just do your best. If you have rocks try to look under them as well. This is a good time to clean your pond. After your done you can put your fish back. I know this seems aggressive but it’s better than removing a few then having to continue every year.. You can build a concreat area around your pond to put the iris, that way they rhizome can’t spread by root and clip the seeds as they grow in. You can also put them someplace else. Just remember wherever you put them they will spread like crazie unless proper precautions are taken. Now that they irises are removed you can put other water plants like lilies, try to use native, no invasive plants.i planted my water ires this year prior to me finding out anything about them. I didn’t plant mine in water yet they still blosumed. I try to soak them at least every other day. They are beautiful to look at, and there is no signs of damage even though they aren’t in water. Best of luck

  9. Hi I have a 6ft iris in a pond basket how deep can I out ut under the water in my pond , it came from a pond where it was 3ft down cheers todd

  10. Can you remove the seed pods and place amongst rocks forming our lake break wall to start a new plant? If so when would be the best time?

  11. My yellow water iris bloomed last year and there are big seed pods on the end of the stalks should I have cut them down in order to get more flowers this year

  12. HI I am still unclear how deep in the water the water iris in baskets should be put. I have a half wine barrel lined with plastic with 4 goldfish and it has two small underwater plantlets. Readjng up it looks like the reason the water is green and has algae is becasue I dont have snough greenery. Wanted to put somr water iris in but unsure of the planting depth and how many plants. Please can you help Thanks jt

    • Yes. You can cut back old and dying leaves. Come winter, you can cut the plant way back to about an inch or two above the crown.

  13. I just purchased an iris and put it into a ceramic container with no basket. There is one inch of water floating on top from the soil to the ankles of the plant. What can I do to prevent mosquitos in this one inch of standing water?

    • Mosquito donuts can be purchased from a nursery or home improvement center. Use these to prevent mosquito larvae from maturing should a momma decide to lay her eggs in your container

  14. We have had water iris in our pond for several years, but we have noticed in the past couple of years that they are not blooming like they used to. Is there a reason for this or something we need to do?

    • It depends on the breed of iris but typically irises can live in around our out of water. They just like to live in a substrate that is high in moisture. Wet is good, moist is good, dry is bad.

      • The water iris in the pot never bloomed. The water irises not in pots took over the pond and some bloomed. I just don’t know the right way to handle these plants evidently. They have reduced the water level a lot because the massive roots have filled up the bottom of the little pond. Completely overshadowed the poor little water lilies and lotus. White water lilies, so they can be just as invasive as yellow ones.

  15. I have recently started a small container aquatic Gardens with just water irises in it and I’m wondering with what do you fertilize it with

    • There are several type of irises. The ‘water’ variety do best in moist to wet soil. Be careful planting directly into the garden though. They can spread and may be hard to control.

  16. I have a small backyard goldfish pond. About 750 gallons give or take 100 gallons with about 15-20 goldfish. I dug out the pond and put down in a pond liner about 6-7 years ago. It’s a bit larger and deeper than the per-built pond you have. I also have a submersible pump to circulate the water. I made a small waterfall from returning water from the pump. Two things you may consider. Add a submersible pump to circulate the water. Second, get rid of the algae bloom.
    I had to do some research to remove the Algae bloom from my pond. I first tried using the chemicals to treat algae. It killed all my plants. Next I tried the tablets. This was a waste of time and money. I found there are two types of pond Algae: “String Algae” and “Bloom Algae”.
    String Algae isn’t that harmful and grows on porous rocks and cement/brick blocks. It is sometimes preferred to leave alone, since it looks natural. I generally leave it alone unless it gets too thick on some of the rocks.
    Bloom Algae is the culprit. This makes the water look green, like pea soup. A natural way I found that works is to use Barley Straw wrapped Bundles. You can get these “Barley Straw Bundles” on-line. Just drop a small bundle into the pond. It floats at first. Then it slowly stars sinking. In a few days it will keep sinking and eventually sink underwater in about a week. The barley straw releases some type of enzyme that reacts with the water to suppress algae bloom. It stinks when you lift it out of the water, so leave it in the water. After it sinks take it out and let it dry in the sun for a couple days. They reuse it. I usually keep a few barley straw bundles around. When one sinks I take it out and replace it with another dry one. Keep doing this all summer long. If your pond already has algae bloom, using the barley straw may take a couple week to get rid of it.
    Another thing I use is a liquid “Barley Straw Extract”. I also get it this on-line and use it to supplement the barley straw bundles. I just pour a little in every few weeks.
    Since I‘ve been using the barley straw bundles and extract for many years now and haven’t had a problem with algae bloom since.
    Good Luck

    • Thanks for your advise. We found out that green clean granular algae cide. It is safe for plants and goldfish and even tadpoles. Some how we even got a bull frog. After you coat the the alge with it turn the pump back on after 30 minutes. Wait two to five hours and then add beneficial bacteria. We do this twice a month unless you happen to get an algai bloom. All of this is safe for the enviroment and pets also.

      • Try using hydrogen peroxide. Ive read that thats what the barley breaks down into anyways. As it decomposes. I just pour in a bottle(depending on gallonage of pond) or two near the pond pump. That way it gets circulated quicker. Do not pour directly on fish or plants as it will burn the plants and will remove the protective slimy stuff on fish

    • A bio force pond pump with uv light circulating the water gives you a clear pond guaranteed I have this for nine years and a perfect results

    • You should plant them in very early spring. You could probably germinate them indoors at the end of winter and then transplant them outdoors. Be aware of where you plant these in your garden – given the chance the seeds could run down a stream and take root. This is not good if the plant is not a native to the area.

  17. Nice article. I would like to suggest one point, If you’re transplanting multiple bulbs to the same hole, point the leaf ends of the rhizomes away from one another for successful growing.

    • I am new to ornamental goldfish pond water plants. I have a black plastic pond we bought at Lowes 2 mos. ago and have tropical plants planted in dirt around the outside of the pond to help shade partly. But I am having a lot of trouble with my pond turning green. I have several water Hyacinths floating on top and try to keep the yellow leaves cut off and clean the roots back when they get too long and collect junk on them and have been pretty successful with blooms. But ever since I added the Hyacinths and also added a umbrella water plant for shade and then added a water lily and and water Iris. I wasn’t sure how to plant the water Iris without losing dirt and the plant leaves are doing fine but it has not bloomed. We’ve had very hot weather for a month. I put the plant down in a plastic pot and added rocks on top to hold it down in the water, but it is in a shallow part with the pot totally covered about 2 – 3 inches above the edge of the pot. The frogs love to lay and sun on the pot edge. We have 3 resident water frogs living in the pond. So I’m wondering if I needed to add dirt to the water iris of if it can live just in the water alone in the pot? Also wondering why my Lotus I recently added is not doing anything other than the leaves are curling up and turning yellow, no blooms, I’ve had it for 1 – 2 1/2 mos down in the pond about 4 – 6 ” under water. My water lily has stopped blooming, and my pond water is green and not clearing up with algae control ingredients. I put 5 goldfish in 3 days ago and 2 have already been found floating on top dead. My husband checked the PH and it was too high which prob. killed the 2 fish. I expect i may find another dead one tomorrow unless the PH goes down.. SO I am enjoying my new pond but having lots of issues, it does have a small waterfall that flows over into the pond with a pump down in the big part of the pond pumping the water up into the waterfall tub. So I am open to any and all comments and suggestions for my problems. Thank You.

      • Green water or algae blooms usually means there are too many nitrates in the water. Nitrate levels go up when there is rotting plant material in the pond, excess fish food and of course fish waste. It sounds like you are doing a good job of removing that from the water. Adding some shade is also good because it will limit direct sunlight from hitting the water surface. Direct sunlight is also a reason for algae growth. It’s good you are testing the water for PH and doing what you can to get those levels in line. Goldfish are pretty hardy and can live in a wide range of PH levels but do prefer neutral PH levels. It could be you over stocked the pond which resulted in low oxygen levels in the pond. It’s hard to tell but ensuring the water is optimal will help keep the fish alive. Also, algae in general uses up a lot of the oxygen in the water even though they also help produce it. In respects to all the plant questions, we are not technically plant experts but we might be able to help. Water iris naturally grow in the margins in wet soil. Using pond plant baskets with appropriate planting medium will help. You can add some gravel or rocks to the top to help keep the soil from escaping into the pond. I would talk to a real plant expert to resolve your other plant questions. Typically though when things don’t bloom or leaves curl up and die, it’s a sign of havinng the wrong soil composition (too much or too little of certain nutrients/fertilizers in the soil).

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