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Growing Irises
How to Plant, Grow, and Care for Irises
How to Plant, Grow, and Care for Irises
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The tall, beautiful iris, named after the Greek goddess who rode rainbows, comes in many magical colors. Here’s how to grow irises in your garden!
Every gardener wants this pretty perennial. Despite its divine origins, it is hardy, reliable, and easy to grow. Irises also attract butterflies and hummingbirds, and make lovely cut flowers.
There are some 300 species in the genus Iris. The most familiar irises are the tall (at least 28 inches) bearded irises (Iris germanica).
The distinctive flowers have three large outer petals called “falls” and three inner upright petals called “standards.” The falls may have beards or crests. Bearded iris are so-called because they have soft hairs along the center of the falls. In crested iris, the hairs form a comb or ridge.
Most irises flower in early summer. Some—mostly bearded hybrids—are remontant, flowering again later in the summer.
Planting
When to Plant Irises
- Plant irises in mid- to late summer. This gives them plenty of time to get established before the coming winter.
- If you receive bare rhizomes or irises in a container at some point earlier in the year, go ahead and plant them as soon as convenient. It’s better to get them in the ground rather than wait until the ideal time.
Choosing and Preparing a Planting Site
- Irises will bloom best in full sun, but can tolerate as little as half a day of sun. Without enough light, they won’t bloom.
- Bearded irises must not be shaded out by other plants; many do best in a special bed on their own.
- They prefer fertile, neutral to slightly acidic soil. Learn more about preparing soil for planting and organic soil amendments.
- Soil drainage is very important; irises prefer “wet feet, but dry knees.” Loosen the soil with a tiller or garden fork to a depth of 12 to 15 inches, then mix in a 2- to 4-inch layer of compost.
How to Plant Irises
- Plant rhizomes singly or in groups of three with the fans (leaves) facing out, 1 to 2 feet apart, depending on the size.
- Dig a shallow hole 10 inches in diameter and 4 inches deep. Make a ridge of soil down the middle and place the rhizome on the ridge, spreading roots down both sides. Fill the hole with soil and firm it gently, leaving part of the rhizome and the foliage uncovered.
- Tip: It’s easy to make the mistake of planting irises too deeply. The rhizomes of these plants should be partially exposed to the elements, or thinly covered with soil in hot climates. If they’re buried too deeply, they won’t do well.
- Water thoroughly.
- At time of planting, top-dress with a low-nitrogen fertilizer, and again in early spring, 6 to 8 weeks before blooms are expected to appear.
Care
How to Grow Irises
- Avoid applying high-nitrogen fertilizers to the surface or carelessly mulching with organic matter, which may encourage rhizome rot.
- Keep rhizomes exposed. Unlike bulbs, which thrive deep underground, iris rhizomes need a bit of sun and air to dry them out. If they’re covered with soil or crowded by other plants, they’ll rot. Irises may benefit from shallow mulching in the spring.
- Don’t trim iris leaves after they have finished blooming. Leaves carry on photosynthesis for next year’s growth. Cut off brown tips—and cut the flowering stalk down to the rhizome to discourage rot.
- If iris foliage is hit with heavy frost, remove and destroy it to eliminate borer eggs. See your local frost dates.
Dividing Irises
Over time, it’s not unusual for plantings of iris to become overcrowded, which causes the rhizomes to lose vitality and stop blooming. When this happens (usually every 2 to 5 years), it’s time to divide and replant healthy rhizomes in fresh soil.
- Shortly after blooming (mid-summer), carefully dig up the clump of irises. You’ll find that the original rhizome that you planted (the “mother”) has produced several offshoot rhizomes.
- Separate these rhizomes from the mother with a sharp knife and discard of the mother, as it will no longer produce blooms.
- Inspect the rhizomes for any rotting tissue or other signs of disease, removing and discarding infected parts or entire unhealthy rhizomes.
- Trim the iris foliage down to 3 to 5 inches in height so that the plants can focus on establishing new roots.
- Plant these fresh rhizomes in a new bed, replant them where they were before (after adding new soil), or share them with friends and spread the joy of irises!
Pests/Diseases
- Irises are deer-resistant and drought-tolerant. However, they are susceptible to borers, so check the rhizomes (fleshy roots) yearly for holes, discarding any infested ones.
- Verbena bud moth, whiteflies, iris weevil, thrips, slugs and snails, aphids, and nematodes may also be troublesome.
Recommended Varieties
- ‘Immortality’ is a tall bearded flower that offers pure white flowers and reblooms in the fall. Grows best in Zones 4 to 9.
- Other rebloomers, hardy at least to Zone 4, are: ‘Feed Back’, a dark purple; ‘Earl of Essex’, also purple; and ‘I Do’, with white flowers.
- If you live in Zone 5 or warmer, try ‘Jennifer Rebecca’, a mauve pink beauty.
- Siberian Irises also come in a range of colors and are distinct from the more common bearded irises.
Wit & Wisdom
- The iris is depicted in the French royal standard fleur-de-lis and is also the symbol of Florence, Italy.
- Oral root, taken from the dried roots of Iris ‘Florentia’, was considered a cure for blood and lung diseases, and teething babies were encouraged to gnaw on a “finger” of dried root for its natural fluoride.
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Reader Comments
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Pests
I have heard that critters can dig up bulbs for food. Is there anything I can do to lessen the possibility until my flowers are established?
Round-up---will it "kill" irises. I have a bed where they are
I have a bed where they are growing beautifully----problem IS- I have a plant called "camilion plant" (it's colorful but very annoring that ' s spreading EVERYWHERE , even into the grass nearby dispite the edging in place. Please advise..... I've tried digging it up by the roots last year---that
doesn't work, IT keeps coming back in abundance, and SPREADING!!!!!!
What can I do to get rid of this invasive plant.?????
Chameleon Plant
As you’ve seen, the dreaded chameleon plant (Houttuynia cordata) is a very, very invasive plant. Unfortunately, other than repeatedly and diligently pulling up and disposing of the plant (in a fire or the trash; NOT in your compost pile!), there’s not much you can do to get rid of it. If grown in a container, it can be kept in check, but once it’s already got its roots in the ground, it will keep spreading.
We do not recommend using chemicals in this case—chameleon plants have been known to survive most herbicides, but using one will certainly damage the other plants in the bed (including irises).
Dutch Iris? Dividing
I have a small 10-12 inch tall iris clump that is heavily infested with grass. How do I best clean it up. I would post a picture, if possible.
Cat litter on iris
I read somewhere that cat litter is good for irises. ??
Cat Litter for Irises
Hi Patrice,
There is some discussion about certain types of clay-based cat litter that can be used to plant irises in water (such as a backyard pond), but we wouldn’t recommend using cat litter on irises. Cat litter is highly absorbent and would most likely absorb all of the water around the plant’s roots, which would be harmful. We hope this helps!
Tall blue flag iris
I encountered very tall blue flag iris in Quebec. They were at least 40 inches tall. The ones described on your site are 28 inches tall. What plants was I seeing in Quebec? Where would I get them? Thanks for your time.
the tallest irises
Thanks for bringing this to our attention. What you may have seen are Iris Spuria, aka salt marsh or butterfly iris, native to central and southern Europe. They reach 3 to 5 (some sources say 6) feet in height, produce “beardless” flowers in bluish purple/lilac hues as well as white, wine, and brown. These bloom one to two weeks after Tall Bearded Irises. Search the Web; several nurseries offer them.
keep iris color they seem to bloom white the next year
how to keep the colors of the iris keep them from all blooming white the next year
question about pruning iris
I live in South Carolina and my iris have tall green leaves all year round -- few seldom get brown or die back -- is there ever a time that these leaves should be pruned?
when to prune
In mild climates, the foliage may remain green throughout the winter. You can remove dead or damaged leaves at any time, bu you should cut back the foliage in fall or early winter. (If you have never done this and the plants bloom well, wait until fall; don’t do it now.) Every few years, make a habit of dividing them, too.
Storing iris
We are moving, it is late fall here. I would like to take some iris with me but don’t know how long it will be before we take possession. Can I take them up, clean off the roots and keep them for any amount of time? By the time we actually get in it might be frozen here.
How to store CO Irises this fall to plant in E. Texasnext Spring
I live in Littleton, CO which is southwest of Denver. I have many friends/family in East Texas that I would like to share my irises with after I divide them in early October. How do I store them until I can get them to East Texas next Spring? Is spring a good time to plant them in East Texas? Thank you.
Digging up Irises
I have a small garden of iris and gladiolas which are not doing well at all even though the iris were divided and they are fed with Bulb Tone each fall and get plenty of sun. There are also lots and lots of weeds in the bed. I am thinking of digging the iris and glads up now and overwintering them so that I can use an herbicide of some sort (?Round Up?) to get rid of the weeds once and for all. Is this a good idea? And if so, please advise on how to successfully overwinter these plants. Thanks!
I have a similar MESS from previous owner.
Like 'Sally in VA, I hv a similar mess, left by the previous homeowner. Since it is at the bottom of a slope, I plan to dig up the entire mess and replace, instead with a hybrid "blood iris"-more tolerant of clayish soils, more tolerant of an occasional dry spell. I'd not thpught about those weeds coming back! (I'd not use toxic Round Up on anything except, maybe rampant English ivy.)
Round Up
Never use that poison. Scientists are publishing studies claiming RU can lead to autism and cancer. It’s a terrible product, banned in Europe. Why is it not illegal. Only greed allows it to be sold in this country.
No Round Up
Please don’t use Round-Up. It’s a poison and studies are finding more and more serious health impacts for humans with Round-Up use. It’s just plain dangerous to babies.
Use of Round Up
Please do not use it. Round -up is connected with some type of Leukemia. In Spain is a lawsuit regarding this product.
Moving irises
We are moving this month but won’t be in new home until December. Will my irises be successful in pots over the winter? How should I plant them in pots? Where should I store them while we are in transition? Should I use most of the original soil?
Weed killer
A more natural weed killer is 1 gallon vinegar, 2 cups epson salt and 1/4 c dawn dish washing liquid (the blue one). Never use round up again.
Natural weed killer
Will this harm surrounding plants? There are roses and coral bells nearby.
Irises: how long does it take for them to bloom again
After digging and dividing. Some I replanted last fall only had green leaves. Do you think they will bloom next spring?
Blooming Irises
As long as they are kept in good conditions, they should bloom next year! Try giving them a boost with some balanced fertilizer as soon as the ground unfreezes next spring.
Tall iris from bulb
I was given some iris bulbs over 30 years ago. They are stunning with huge flowers and leaves shaped like green onions and the bulbs are covered in a rich shiny mahogany colour and they grow 24-28” tall. I think she said that they are Siberian. Does anyone know what they could be. I’d appreciate any information. They are very prolific and need dividing every few years. Anything you can share is much appreciated. Thanks.
Old Siberian Irises
I forgot to add that the colours are exquisite with the deepest most intense indigo purple and the yellow is magnificent so deep and brilliant. Thanks. Sharon
Tall Iris from bulb
These sound as though they are Dutch Iris.
Tips to help Irises establish after being dormant for over year
We have had our iris bulbs out of the ground for over a year due to building new house. It's time to get them back in ground so they can grow and bloom. Any tips or ideas to help them grow / get establishe better?
Planting Irises
You’ll want to make sure that the planting site is in a sunny spot with well-draining soil, as irises don’t like to stay wet. Break up the soil before planting so that the irises’ roots can spread more easily. Mix in compost before planting, in a ratio of about 2 parts soil to 1 part compost. You may also want to add a small amount of slow-release balanced fertilizer at planting, which will give the irises something to feed from later on. Since they’ve been out of the ground for so long, they may not all come back in the spring with the vigor they would normally have, but in the future, they should do great!
Rhizomes ready to pant
I bought new rhizomes Aug. 8, can't plant til Sept. 4. How do I keep them healthy until then?
Rhizomes Ready to Plant
I wouldn't worry. Irises are very hardy. Someone gave me a box of iris rhizomes about five years ago. I didn't have time to plant them and just put the box of them underneath our crabapple tree where they got some moisture and a little bit of light. The second spring they were blossoming through what was left of the box. Even ones at the bottom sent out stalks. It was the funniest sight.
You can just keep them in your garage or out of the sun until you are ready to plant. You don't even have to water them.
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