How to Grow and Care for German Bearded Iris

Iris x germanica

If you’ve ever marvelled at a massive, colorful, frilly iris in USDA Hardiness Zones 3 to 10, chances are pretty high that you were looking at a German bearded iris.

One of my favorite parts about growing German bearded irises is that they’re so robust and prolific that I am always sharing mine with friends and neighbors.

In fact, my community has a yearly iris exchange so we can spread the fun.

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Our guide to growing irises covers how to cultivate these easy-going, colorful flowers.

In this article, we focus on Iris x germanica, the hybrids commonly referred to as German bearded irises.

Here’s what I’ll cover:

The original species, I. germanica, is rare in cultivation.

While we’re on the topic, the original isn’t a true species at all, but a natural hybrid of sweet (I. pallida) and Hungarian (I. variegata) iris species.

Today, the German bearded iris that you’ll find in stores and most gardens is a cultivar of I. x germanica and not the original hybrid.

Despite the specific epithet, germanica, which would imply that it originated in Germany, the hybrid originally hails from the Mediterranean and Balkan region.

It has naturalized throughout Europe and parts of the US.

Because there is so much variation among the hybrids and cultivars, it’s hard to sum up what your plant might look like, though.

Most will bloom once in mid- to late spring, but reblooming types that send up a second round of flowers in fall are becoming more common.

A flower stalk might hold a single blossom or there might be as many as a dozen flowers.

The leaves will either die back to the ground in the winter, or in some regions, will remain throughout the entire year.

They’re generally about two feet tall when in bloom, but you can find itty-bitty dwarf cultivars and towering tall varieties.

While the original came in hues of purple, modern cultivars can cover the rainbow, including white, yellow, salmon, pink, and every shade of purple under the sun.

With irises, it helps to know some terminology.

How to Grow

German bearded irises are easygoing provided that you put them in the right soil and light exposure.

Light

While some iris species will tolerate a bit of shade, German varieties need full sun.

They will survive in partial shade but the flowering will be greatly reduced and they can be susceptible to pest and disease problems.

So choose a location with plenty of sunshine. In super hot regions, a little afternoon shade won’t hurt.

Soil

Unlike some of its relatives, which thrive in soggy soil, German irises need well-draining soil.

They won’t tolerate standing water. While they won’t tolerate wet roots, the plants are a bit more forgiving when it comes to soil composition.

A bit of sand, or a touch of clay is fine, so long as the soil is humus-rich and the drainage is on point.

Feel free to amend the soil to improve its texture and remove any big rocks. Just don’t add mulch to the top of the rhizomes. This will invite rot.

The soil should ideally be slightly acidic to neutral, with a pH between 6.0 and 7.0 for best flowering.

Water

Not only do German irises prefer well-draining soil, but they can even tolerate drought. When providing water, wait until the soil is almost completely dry before adding more.

The exception is with plants or rhizomes that you’ve just put into the ground. Keep these lightly moist for the first year.

Fertilizer

Feed once a year after all of the flowers have faded using a flower-focused fertilizer.

I’d highly recommend that you do a soil test before feeding, because overfertilizing can lead to poor flowering and stress.

A soil test will tell you how much fertilizer to use and what nutrients your soil is lacking.

Down to Earth Flower Garden

If you prefer not to test, pick up something like Down to Earth’s Flower Garden food in one- or five-pound boxes at Arbico Organics and follow the manufacturer’s directions for application.

Cultivars to Select

When you’re out shopping, you will probably encounter some interesting terms used to categorize these plants.

First, they will be categorized by size.

Then they will be described by color.

Bicolor has contrasting standards and falls, bitone has different shades of the same color standards and falls, plicata has spotting, dots, or stippling.

Self is all one color, amoena is white, and variegata has yellow standards and purple, red, or maroon falls. 

You can learn more about iris classification here.

Here are some of my favorite cultivars:

Bernice’s Legacy

‘Bernie’s Legacy’ certainly is a looker! The overall hue is wine red, but it’s accented with ruby, garnet, cinnamon, and persimmon.

Not only are red irises a bit unusual, but this is also a reblooming variety.

‘Bernice’s Legacy’

It’s a tall type that can reach an astounding three feet in height.

You can find ‘Bernice’s Legacy’ in one-gallon containers available at Nature Hills.

Black Suited

Irises are known for having some extremely dark flowers and ‘Black Suited’ is one of the darkest.

The color is so inky purple that it looks almost pure black. It also has a hint of musky floral fragrance, which kicks it to the top of my cut flower list!

This self-colored tall type grows up to three feet tall. It was bred in 2000 out of ‘Black Tie Affair’ and ‘Before the Storm’ by noted hybridizer Sterling U. Innerst.

‘Black Suited’

‘Black Suited’ was awarded honorable mention by the American Iris Society in 2003.

You can find ‘Black Suited’ bulbs available at Eden Brothers.

Bounce

Sweet, stunning ‘Bounce’ has a delicate fragrance but a bold look.

The standards are a deep rose to garnet hue and the falls have a garnet-amethyst color with cinnamon-bronze accents and a bright violet stripe down the center.

‘Bounce’

This intermediate type grows about 25 inches tall and was bred by Australian hybridizer Barry Blyth in 2003 out of ‘Gaelic Jig’ and ‘Wee Stroll.’

Snag yours from Eden Brothers.

Cybergrape

There’s purple and then there’s purple. ‘Cybergrape’ is a hyper-colored iris that practically glows with blue-purple standards, violet-purple falls, and a light blue beard.

The petals have heaps and heaps of ruffles, adding to the elegant appearance.

‘Cybergrape’

It was bred by Schreiner’s Iris Gardens in 2016 out of ‘Royal Snowcap’ and ‘Sea Power,’ and was awarded an honorable mention by the American Iris Society in 2021.

Eden Brothers carries ‘Cybergrape’ bulbs in packets of various sizes.

Maui Surf

With a deep blue-lavender hue, ‘Maui Surf’ brings to mind the ocean waters of Hawaii at sunset.

This tall type grows up to 26 inches in height with self coloring. The petals are all heavily ruffled.

It was bred by J. Terry Aiken in 1990 out of ‘Memorable’ and ‘Orbiter,’ two garden stalwarts.

‘Maui Surf’ is such a beautiful and reliable bloomer that it nabbed the coveted Royal Horticultural Society’s Award of Garden Merit in 2004.

Pure As Gold

Is yellow your thing? Then you won’t find a better option than ‘Pure As Gold.’

It features heavily ruffled, golden yellow self blossoms that stand atop stately 33-inch tall stems. This one is a rebloomer that gives you a second show in autumn.

‘Pure As Gold’

California hybridizer William and Marilyn Maryott brought this beauty into the world in 1993 after crossing ‘Radiant Energy’ and ‘Sound of Gold.’

It snagged the American Iris Society’s honorable mention in 1995 and the Award of Merit in 1999. You can find ‘Pure As Gold’ available at Nature Hills Nursery.

Starring

All eyes are turned to the garden stage as ‘Starring’ takes on her role.

Bred by hybridizer Joseph Ghio of California out of an unnamed seedling and ‘Bay View’ in 2000, it nabbed the American Iris Society’s Award of Merit in 2004, Favorite Guest in 2004, and the highest award, the Wister Medal, in 2007.

So what makes it so special? It starts with the pure white standards and amps things up with near-black, purple falls with hints of indigo between the veins.

‘Starring’

All this is topped off with a brick red beard. This tall type grows to three feet in height, adding to its commanding presence.

If your garden needs a star, pop over to Eden Brothers to pick up some bulbs for fall planting.

Maintenance

After the flowers fade, cut off the stalks at the base. This helps redirect the energy into the roots rather than into developing seeds. Strong roots mean stronger leaf and flower growth.

In areas where snow accumulates, cut the leaves back to about four to six inches tall in the late fall.

You don’t strictly have to divide the rhizomes, but it will certainly result in better flowering.

Each year, the plant will develop more rhizomes and when they become crowded, flowering and leaf growth is greatly reduced.

If the flowers are looking a bit disappointing, make sure the rhizomes aren’t too deep and that the plants aren’t in too much shade.

Sometimes, you’ll plant in full sun, but as trees grow larger or a neighbor plants a new shrub, suddenly the sun exposure is different.

Propagation

There are so many options when it comes to choosing a German bearded iris, but for propagation, you have three choices:

From Rhizomes

Rhizomes should be put in the ground in the late summer or early fall.

Dig a hole about four to six inches deep depending on the size of the rhizome. You want it to be just covered by the soil but not buried too deep.

When in doubt, allow the tippy top of the rhizome to poke out of the soil. It’s better to plant too shallow than too deep which can lead to soft rot.

Place the rhizome in the hole with the roots facing down and bury it.

The rhizomes should be about 12 to 24 inches apart, depending on the size of the mature plant.

By Division

Divide your common flags in the summer after flowering.

Before you start digging, trim the leaves back to about two-thirds of their height. This reduces the potential for damage and the amount of foliage that the roots need to feed.

Gently dig up the entire clump of rhizomes. Generally, the rhizomes won’t extend more than a few inches beyond the leaf clump, and they grow about eight to 12 inches deep.

Brush or wash the soil away and gently tease apart the clumps using your hands.

Cut away any soft or rotten rhizomes.

Replant the rhizomes as discussed above. If you have too many, just pass them along to a friend or neighbor.

Learn more about dividing irises here.

Transplanting

If you find potted plants, put them in the ground whenever you purchase them. You don’t need to wait until the fall.

Dig a hole the size of the container the plant is currently growing in.

Remove the plant from the container and gently brush away some of the soil and set the plant in the hole.

Pests and Disease

Irises are deer- and rabbit-resistant. That’s just one small part of what makes them so fabulous.

Now, however, we need to talk about the not-so-fabulous aspects of iris growing.

Pests

The iris borer (Macronoctua onusta) can cause massive destruction.

The adult is a night-flying moth with chocolate brown wings that lays eggs in late summer on iris plants.

These eggs hatch in the spring and the larvae emerge. The larvae are pink, caterpillar-like creatures that can grow up to two inches long.

The caterpillar crawls up the branches, feeding as it goes, and then tunnels down into the rhizome, continuing its destructive feeding.

This makes holes and tunnels in the rhizome that can fill with water and cause it to rot. As the rhizome rots, the leaves will turn brown and soft.

In the spring, look for small holes in the leaves. If you catch the larvae at this early stage, you can squash them inside the leaf. They move into the rhizome by early to midsummer.

If you see browning or yellowing of the leaves, dig up the rhizomes and examine them for tunnels. If you see any, discard the rhizome.

In the winter, make sure any dead leaves are cleaned up and disposed of. In the spring and late summer, introduce beneficial bacteria into the soil to kill the larvae.

There are several species of beneficial nematodes that are used in pest control, and you should choose a product that contains all three, like Arbio Organic’s Triple Threat, which has Heterohabditis bacteriaphora, Steinernema carpocapsae, and S. feltiae.

Triple Threat Beneficial Nematodes

You can pick up packs of five to 500 million at Arbico Organics. Be sure to follow the instructions carefully,

Disease

If your plants are troubled by pests, it opens them up to disease issues. Let’s talk about a real scary problem first:

Bacterial Soft Rot

If borers are the biggest pest threat, bacterial soft rot is the most serious disease you’ll face when growing German bearded irises.

The good news is that it’s really easy to identify. The plant will look sad, wilted, and discolored. But more than anything, it will stink. I mean really, really stink.

The bad news is that there’s nothing you can do to cure bacterial soft rot. You’ll have to dig up the plant and dispose of it in a garbage can. Don’t put infected plant material in the compost.

To prevent bacterial soft rot, make sure the soil is well-draining, the rhizome isn’t planted too deep, and avoid overwatering. And keep those borers far, far away.

Mosaic 

Iris mosaic disease is extremely common and occurs anywhere irises grow.

It’s spread by aphids. You should do your best to keep aphids off your plants, but that can be a difficult task and it only takes one bite to spread the virus.

An infected plant might not have any symptoms. When they do appear, you might see yellow streaks on the leaves or mottling or steaks on the flowers.

The symptoms might disappear and reappear from year to year, but once a plant is infected, it can’t be cured.

In extreme cases, or if you want to help limit the spread of the disease, you’ll need to pull and dispose of the infected plant.

Versatile and Vibrant Irises Light Up Your Garden

One of the biggest strengths of German bearded irises is their versatility. Looking for a border plant? You got it.

Need something petite to add interest to the front of a garden? Here it is. Adding to a cut flower garden? Or a cottage garden? Check and check.

Are you growing German bearded irises? If so, which types are your favorites? Let us know in teh comments section below!

And for more information about growing irises in your landscape, add these guides to your reading list next:

• How to Grow and Care for Douglas Iris
• How to Grow Rock Garden (Reticulated) Irises
• 33 of the Best Iris Cultivars for Your Garden