Horticulture Magazine

Bearded Iris Plant Care & Growing Tips

showy pink bearded iris flowers

Bearded Iris Overview

Official Plant NameIris Germanica
Common Name(s)Bearded Iris
Plant TypeBulbs / Perennial
Native AreaMediterranean
Hardiness RatingH6
ToxicityToxic when eaten. Gloves should be worn when handling
FoliageUpright and evergreen
FlowersUpright and dropping petals. Fragrant, showy flowers
When To PlantJanuary, February, March, April, October, November, December
Flowering MonthsMay, June
Sunlight

Preferred
Full Sun

Exposure
Exposed or Sheltered

Size

Height
0.5 – 1M

Spread
0.1 – 0.5M

Bloom Time
May – June

Soil

Preferred
Clay, loam

Moisture
Moist but well drained

pH
Neutral / Alkaline

One of those flowering plants that needs no introduction, Iris numbers among its categories a type that is a garden classic and favourite: Bearded Iris.

This rhizomatous plant is remarkably fuss-free about soil, watering or anything else. Yet it bears breathtakingly beautiful blooms that have a vertical orientation and come in an astonishing range of hues, with many cultivars producing even multi-coloured, patterned flowers. 

The Iris Genus

Genus Iris comprises over 320 species and unknown tens of thousands of cultivars, and this very fact clues one in to the abiding fascination floriculturists and gardeners have with Iris. All these many varieties of Irises are divided into numerous groupings of which the Bearded Iris is emblematic of the genus. Indeed, Bearded Iris itself is further subdivided into six sub-groups.

While Bearded Iris is a rhizomatous plant and is the one most often found in gardens, floristry also makes heavy use of the bulbous ‘Dutch’ Iris. The British Isles has its very own group of Irises, ‘Yellow Flag’. The present article relates principally to Bearded Irises.

The Iris genus is classified under Family Iridaceae. This family is one of those that takes pride of place among the families of flowering plants because it includes – besides Iris – crocus, gladiolus, freesia, syringa, and even more flowering plants.

Like Iris, many of these other genera include herbaceous perennials. Similar to those genera, Iris bears long strap-like or sword-shaped leaves of a sea-green or bright green hue, sometimes with a bluish tinge. These leaves grow in a ‘fanned-out’ arrangement.

Iris species occur almost throughout Asia, Europe, and North America. Quite a number of nations and peoples attach considerable religious or political significance to their native Iris species. This may well be because of the habit and form of the plant and, even more, because of the shape, form, and hues of the unusual flowers.

For example, the Fleur-de-Lis, which is a stylisation of Iris germanica, was borne on the coats of arms and pennants of French and British royalty, while white Iris albicans flowers are laid on Muslim graves in Iraq, Iran, and the Levant, just as they have been for centuries. 

lilac coloured bearded irises
Beautiful Bearded Iris Blooms – You Can Almost Smell the Fragrance

The Bearded Iris Flower

Perhaps part of the unique charm of Irises is that the flowers are vertically asymmetric but laterally symmetric, and are intricately ‘designed’ with frilly or ruffled, fanned-out petals. Three outer petals fall outward and downward; not surprisingly, they are known as ‘falls’ in the trade. Three inner petals stand erect behind the ‘falls’, and these are called ’standards.’ (As it happens, the word ‘standard’ also means the emblem or insignia carried on a coat of arms or a pennant – and stylised Iris itself was and is such a ‘standard.’)

Just as the ‘flagship’ Iris group is considered to be the Bearded Iris, the signal colour of this genus’s flowers is surely purple. Though Iris varieties abound in shades of purple and violet, this flower also occurs in an astonishing range of colours including whites, pinks, yellows, oranges, tan, plus that rarity among flowers, true blues, and even dramatic near blacks. 

As for Iris’s signature colour, Mother Nature goes a step further with bicoloured and reticulated Irises. Some varieties exhibit a stunning complementary contrast of deep purple and bright yellow on one and the same flower. Indeed, Iris varieties are rich with cultivars whose flowers are multi-hued or gradated, and display streaks, ribbons, flushes, blazes, flecks, venation, and such. Many of them are scented or fragrant, a quality which results in further colour in the garden in the form of butterflies and hummingbirds!

violet Iris Germanica with an old brick wall in the background
Iris Germanica and its Cultivars’ Signature Colour is Surely Purple-Violet 

Varieties

Flag Iris, Water Iris, Siberian Iris, Bicolour Iris, Aril Iris . . . the types and kinds of Iris go on and on. In this guide we focus on Europe’s (and America’s) most popular Iris, Bearded Iris, of which there are so many tens of thousands of cultivars that no-one can keep count!

It should be observed that compared to Bearded Irises, which typify Irises for most Westerners, other types of Irises may not even look like ‘Irises’ at all to the casual gardener. This applies especially to Japanese, Siberian, Louisiana, and Crested Irises.

Bearded Iris has been extensively cultivated to the extent that it is now divided into half-a-dozen groups by plant size, flower size, and blooming season. The American Iris Society’s classification, adopted by the British Iris Society, is as follows:

Miniature Dwarf Beardeds grow up to only 20 centimetres, Standard Dwarf Beardeds have heights from 20 to 41 centimetres; and Intermediate Beardeds from 41 to 70 centimetres. Border Bearded Irises are of the same height range as the Intermediate Beardeds but bloom later in the season with the Tall Beardeds.

Miniature Tall Beardeds are also of the same height range as the Intermediate Beardeds but their flowers are smaller and stems are thinner – they are daintier.

Finally, the Tall Beardeds start 70 centimetres and rise to over one metre, their stalks exhibit more branching, and their large flowers exhibit desirable qualities more frequently than those of the other types.

Miniature Dwarf Bearded Irises
Miniature Dwarf Bearded Iris – Perfectly Suited to a Rock Garden

In general Bearded Irises go into bloom by height, starting from shortest and ending with the tallest. They bloom from the beginning of April to the end of June. However, there are also cyclic bloomers and re-bloomers which introduce a happy variation to the blooming season.

Iris germanica is the mother species. Originally native to the Yugoslavian states, it is now considered to be native to a belt of land from the Adriatic and Eastern Mediterranean eastward up to Pakistan. It attains a height of 70 to 100 centimetres. It blooms in spring, putting out violet flowers with yellow beards. The species is hardy to Zone H6, and varieties, i.e. Bearded Irises, are hardy from Zone H7 to H5. ‘Iris barbata’ is an erroneous supposed ‘synonym’ floating around on the Web.

Underneath we review a Top Ten of Tall Bearded Iris cultivars with a preference for the aesthetic, striking, and dramatic. The blooms measure at least 10 centimetres and sometimes hit 20 centimetres, with a 15-centimetre size being quite common. 

‘That’s All Folks’ growing to one metre or more has nothing to do with Bugs Bunny or Porky Pig. This variety may not bring any ‘extras’ to the table but its big blooms with frilly petals will undoubtedly bring a radiance to the summer garden. And that is because of its warm, intense, and riveting hue of yellow accented with a white blaze on the falls.

‘Absolute Treasure’ grows to a full metre or more. The large flowers are well ruffled. The falls feature creamy white centres but the reason that this flower is a ‘treasure’ is surely that the outer part of the falls and the standards are of a rare floral colour in a rare tone: a very pale, pastel tone of blue.

‘Champagne Elegance’ is aptly named in view of its colouration. It grows to about 90 centimetres. The standards are off-white while the falls are truly of a ‘champagne’ hue, and display yellow beards. Champagne coloured with a hint of orange as it is, this flower appropriately has a lovely orangey scent.

close up of a bloom of ‘Champagne Elegance’ iris
A Bloom of ‘Champagne Elegance’ Exhibiting Falls with Saturated Colour

‘Autumn Tryst’ rises to about 85 centimetres with the welcome qualities of being a re-bloomer and also being sweetly fragrant. The largeish flower is bicoloured as the frilly petals have unusual pearly-white centres gradating into a sparkling tone of lavender. It blooms a second time in end-summer or early autumn.

‘Sugar Blues’ attains a height of about 85 centimetres and it too is a reliable re-bloomer, putting out flowers a second time from late summer. It is also fragrant but of a pleasant, powdery scent rather than an intense perfume. As for the colours, this knockout has a striated white blaze near the centre and also has a white-yellow beard while the petals are a mesmerizing, translucent hue of baby blue. 

‘Immortality’ attains a height of about 75 centimetres, and has multiple desirable attributes. First, it is a re-bloomer that flowers a second time in late summer or early autumn. Next, its blooms are intensely fragrant. Finally, the heavily ruffled blooms are spectacular as they are pure, snowy white with the small yellow beard accentuating the petals’ snowy whiteness.

‘Jesse’s Song’ grows to about 85 centimetres. Though its flowers’ petals are heavily frilled and ruffled, the flowers’ shape is among the finest as the falls are spread out and are relatively firm rather than limp. The medial halves of the petals are a bright white while the outer part is an equally bright purple, with lighter lavender tones and speckling where the two colours meet.

‘Titan’s Glory’ grows to nearly 90 centimetres and it too is quite fragrant. It boasts especially large flowers, even for a Tall Bearded. What is more they are ‘selfs’, so to speak, being unicoloured including even the beard. And this colour is an intense, gorgeous violet that your eyes will feast on.

‘Superstition’ rises to about 90 centimetres and has the desirable trait of a slightly longer-than-normal flowering season. The frilly standards are a deep and vivid gem-like purple with a beard to match while the falls are nearly black, making it one of the most striking and dramatic of Iris flowers.

‘Before the Storm’ attains a height of about 90 centimetres. Its flowers are very fragrant; petals are very ruffled. Though for a Tall Bearded it does not boast large blooms, these blooms are indubitably among the most stunning and dramatic in all Flowerdom, for they are black with delicious chocolate-maroon tinges and tints.

black hybrid iris 'before the storm' in focus with green foliage out of focus
Dramatic and Captivating in Near Black Raiment: ‘Before the Storm’

Where to Plant Bearded Iris

Bearded Irises by themselves, let alone other types of Irises, offer such a wealth of diversity in plant size, flower size, and floral colour (and also blooming season and fragrance) that the best answer is “Wherever you please.” Where you can or should plant Iris is limited only by your imagination. 

A mass planting of mixed bearded Iris in a good-sized bed will provide a truly breathtaking vista of floral form with fantastic colour. They are excellent choices for a mixed bed too provided you pick the right companion plants.

As general guidelines, the taller varieties with their large flowers are very suitable for the rears of beds while the shorter ones are perfect for courtyard gardens. Intermediate-height Irises are usually perfect as companion plants. Intermediate and dwarf varieties are also great for borders. 

Reserve the visually stunning ones such as the taller varieties with near-black, high contrast, and vivid ‘self’ – so to speak – flowers as specimen plants to be planted in containers and set by the doorway or on the verandah or the patio.

It must be said that Bearded Iris is that rare plant that is almost as at home in a formal garden as it is in a cottage garden.

a border in a modern garden with lupins, irises and peonies amongst others
A Colourful Mixed Border Including Bearded Iris

Feeding, Care and Growing Tips

Bearded Irises are most commonly – and very easily – grown from rhizomes. Though it can be an exercise in pampering and frustration to grow Iris from seed, there’s absolutely nothing to growing Irises from rhizomes.

Rhizomes can be planted after they have started to sprout leaves and even push up flower stalks. The advantage in doing so is that a beginner can easily tell which way to plant the rhizome in a bed by simply ensuring that the leaf fan is directed away and outside from other Irises or rhizomes with each one’s ‘nose’ being directed inwards, or place the rhizome such that all are oriented in the same direction. Mid to late summer is the perfect season for planting rhizomatous Iris.

Irises should be planted in full sun. Leaving aside the plant, Iris rhizomes need sun and also good air circulation.

A fertile, clay-free loam enriched with humus or compost is ideal for Irises. No matter what the soil, it must drain very well. Therefore, it is preferable for the soil to have some gravel or similar amendment that will assist in drainage. Soil pH a notch or two from 7.0 is perfect though anything from Slightly Acidic to Slightly Alkaline is fine.

First, loosen the soil down to 30 to 35 centimetres and enrich or amend as required.   

Make a shallow planting hole within which form low, loosely-packed mounds or ridges where you intend to plant the rhizomes. Place a rhizome on the mound or ridge, and carefully spread out its roots evenly. Water very moderately and fill in the hole without packing in the soil such that the upper part of the rhizome to about a good centimetre stays open and exposed. Continue planting other rhizomes similarly.

Iris germanica with pink petals
A Bearded Iris Flower in Soft Pink

The rhizomes can be spaced from 15 to 60 centimetres apart. The closer the rhizomes, the more spectacular the visual impact but you will need to separate and divide the rhizomes within a couple of years. The further apart the rhizomes are, the greater the number of years you can leave them be to naturalise but you will have obvious gaps between the plants. Thirty centimetres is a smart compromise.

Now give the area of planting a good soaking and firm up the soil on the sides of the rhizomes (but not above them) so that rhizomes and plants are held in place. 

Rhizomatous Irises are a little too often made out to be water-guzzling plants but in reality in most areas of the UK they will need only moderate or supplemental watering.

Avoid feeding Irises with nitrogenous fertiliser. An organic or liquid 5-10-10 or plain organic compost are ideal for Irises. Feed them in April. 

On a periodic basis, as and when necessary, the clumped-up rhizomes will need to be divided. With the rhizomes visible at the soil surface, you will know when it’s time to get down to business; however, every four years is a good rule of thumb. The end of summer is the right time for dividing rhizomes.

Do not divide rhizomes when the soil and rhizomes are wet or damp.

First, remove the soil from around the rhizomes. Be sure to carefully loosen a rhizome’s roots and gently lift them, and (only) then pick up the rhizome. You will be able to see a narrower collar-like ‘join’ at an angle on most rhizomes. Simply break or pull apart the rhizome at this ‘join’. Large and long rhizomes may be divided with a sharp, sterilised knife.

a single That's All Folks bearded iris flower
The Sunny, Intense Yellow Bloom of ‘That’s All Folks’

Pruning Bearded Iris

Spent flowers should be deadheaded. In particular, be watchful for seed pods lest your garden gets seeded with Iris plants that will remain unproductive for a good few years.

A stalk that is fully spent may be cut back.

After the flowering season has ended, cut down the stalks. However, do not cut back the foliage at this time as the leaves will continue to photosynthesise through autumn to generate energy which is shipped back to the rhizome for the following year’s blooms. You can certainly trim unsightly tips and tatty leaves. 

As soon as the leaves have withered and browned they should be cut back. This step is especially important to eliminate any Iris borer eggs that may have been laid in the leaves, where they would overwinter and then hatch in spring.  

Remember to wear gloves and long sleeves when pruning this toxic plant.

Common Diseases and Problems

Iris borers and soft rot are the two serious problems that can afflict this rhizomatous plant.

Iris Borers

Though Iris borers in the form of adult moths lay eggs in the foliage, it is the larvae or caterpillars that emerge from them that ‘bore’ through the leaves and stems and into the rhizome. If rhizomes have small but clearly visible holes that look as if made by an awl then the plants have been stricken by Iris borer. Other indicators are a foul smell and an unhealthy sogginess at the base of the stalk. However, the earliest clue, if you can spot it, is foliage that both has tiny holes and appears a little watery and swollen.

Any plant infected with Iris borers must promptly be removed and destroyed. However, if Iris borers have reached the rhizome, they may also well have infested nearby soil. In such cases the soil should be tested for this pest lest it get out of control and attack more and more plants.

Soft Rot

Soft rot is caused by a bacteria which infects Iris rhizomes under the favourable conditions of climatic warmth and dampness. If some rhizome exudes a foul, rotting smell and is soft to the touch, it is almost surely soft rot.

Other symptoms are the central leaves first yellowing and wilting, signs of decay at their bases, and then the whole fan withering.

To address the problem, do as follows on a sunny, dry morning. Cut off the affected part of the rhizome and a little more besides with a sharp, sterilised knife such that the remaining rhizome displays healthy tissue and does not have any foul smell.

If the affected part is too large, the entire rhizome will have to be removed. Also scoop up all the nearby soil. Lightly coat the newly-cut surface and edges with garden sulphur (and put some in the surrounding soil) and leave the rhizome exposed to the sun for the entire day.

Other than these two critical problems, Irises may be affected by a less serious problem namely aphids, and those garden nuisances, slugs and snails.

purple and white jesse's song
The Fabulous Floral Form and White-and-Purple Colouration of ‘Jesse’s Song’

Bearded Iris is Poisonous

Though not a ‘classically’ poisonous plant like foxglove or hemlock, Iris is still pretty toxic from flower down to, most of all, rhizome.

The sap that oozes from stalks and stems is mildly toxic and will cause rashes and other unpleasant symptoms if you let it come into contact with yourself. It is good practice to wear gloves and long sleeves when working with Iris and wash your hands after you are done.

The rhizome is poisonous. Little children and pets are not only more likely than adults to take a nibble on a rhizome, they will suffer its poisonous effects more acutely than healthy adults would. Symptoms of Iris rhizome poisoning include nausea, diarrhoea, vomiting, and loss of energy and body tone. Any child or pet suspected of having ingested any part of a rhizome should immediately be taken to a clinic or hospital.

In view of the toxicity of the rhizomes and the fact that they need to be kept exposed above the soil means that, sadly, parents and cat- and dog-lovers may decide to take a pass on this beautiful plant for the safety of their children and pets.

Where to Buy Bearded Iris

Potted Bearded Irises are among the most widely offered of flowering plants. You are sure to find several different kinds at nearby nurseries and garden centres, all ready to go in pots and containers.

a snow white immortality iris in clear focus
‘Immortality’ is a Very Special Cultivar with Its Pure, Snowy White Flower

Award-winning cultivars are available in the form of rhizomes from specialised horticulturists. They are very easily packed and mailed, and are surprisingly inexpensive.

Finally, it is easy to get Irises from a neighbour or a friend as Iris-lovers usually have extra rhizomes every few years, given the plant’s pleasing proclivity for arithmetic – i.e. ‘multiplication’ and ‘division’!

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