Iris Identification – Which Type of Iris Do I Have?

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Robert Pavlis

Iris are very common in the garden and often people ask for help to plant, grow, move or divide them. The answer to such questions starts with iris identification. There are many different species iris and they do not all grow the same way. Some have tubers and need to be divided regularly. Others are bulbs and hardly ever need to be divided.

Learning how to grow your iris starts with identifying the type of iris. I am not talking about finding out the actual cultivar name, but you do need to know which type of iris you are dealing with.

In this blog I will help you to identify the type of iris you have. In a future blog I will provide cultural advice for each type of iris.

An easy way to identify the type of iris you have, iris identification
An easy way to identify the type of iris you have, source GardenMyths.com

What is an Iris?

When you mention the word iris to most gardeners they will immediately think about the German bearded iris. This iris was so popular in the past that many gardeners think that all iris are German bearded iris. Nothing could be father from the truth. There are many different types of iris and in my opinion, some of the the others are a better choice for the garden.

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From Wikipedia we have the following description for an iris. It is a genus of up to 300 species of flowering plants. Iris are perennial plants, growing from creeping rhizomes or from bulbs. They have long, erect flowering stems which may be simple or branched, solid or hollow, flattened or have a circular cross-section. Iris with flattened leaves, forming a fan, are the most common in gardens.

As you can see from this description iris plants can vary quite a bit.

The term iris is both the name of the genus and a common name used for iris and iris-like plants.

Iris Types

My segregation of iris into types is not based on scientific taxonomic characteristics. Instead it is based on cultural requirements and their popularity in the garden. I will be discussing the following types.

  • Bearded iris – also known as the German bearded iris.
  • Beardless iris – which includes the Siberian, Japanese, and Louisiana irises as well as Iris pseudacorus.
  • Crested iris – Iris cristata and Iris tectorum
  • Dutch iris – Iris hollandica
  • Reticulata iris – early spring bloomers

Iris Identification by Bulb and Rhizome

Iris grow from either bulbs or rhizomes. This difference separates iris into two main categories as shown in the above flow diagram.

How do you know if your plant has bulbs or rhizomes? The surest way to know is to dig one up and have a look at it.

You might not have to dig up the whole plant. Since most iris have rhizomes, start by looking for a rhizome. Look at the soil right at the base of the leaves. Some iris will have the rhizome sitting at soil level or even above soil level, as in the picture below. If you don’t see it, remove an inch or two of soil towards the center of the plant. If you don’t find a rhizome the iris is probably growing from a bulb.

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The length of rhizome between fans of leaves can be several inches long or it can be so short that some people will conclude that the plant has no rhizome.

Bulbs will look mostly round or pear shaped and have a size equal to the tip of your thumb or smaller. They are usually 2-5 inches below ground but they can be more shallow than that.

Bearded iris rhizomes in the center of the picture, iris identification
Bearded iris rhizomes in the center of the picture

Bulbs

There are two common types of iris that grow from bulbs and these are easily distinguished from one another by their bloom time.

If your plant has a bulb and blooms in early spring along with snow drops and before tulips,it is a reticulata type.

If your plant has a bulb and blooms in mid summer it will be a Dutch type.

Rhizomes

Most iris grow from rhizomes and if you have one of these you will need to have a closer look at the flower in order to identify its type. See the next section for more details.

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Iris Identification by Flower Characteristics

Most iris have similar looking flowers but there are a couple of unique characteristics that are used to identify different types of iris with rhizomes and these include the ‘beard’ and the ‘crest’.

An iris has two types of petals called ‘falls’ and ‘standards’. The falls are the three petals that are curved downwards – they are falling away from the center of the flower. The standards are three petals that are standing straight up. In this picture the standards are white and the falls are purple.

Bearded iris with white standard petals and purple falls petals, iris identification
Bearded iris with white standard petals and purple falls petals

In many iris the standards and falls are quite distinct, but in some, like the Japanese iris, the standards are mostly horizontal and start looking like falls. In all cases the standards are the three upper most petals.

What is a Beard?

The beard is a fuzzy patch at the base of each falls petal. Locate the falls petal and look at it near the center of the flower. The beard is usually quite distinct and you can feel the fuzzy hair-like feature.

Don’t be fooled by a color patch in this same location. If the petal is not fuzzy, it is not bearded.

Iris beard - yellow hairy extension on the falls petal, iris identification
Iris beard – yellow hairy extension on the falls petal

What is a Crest?

A crest is raised tissue that is located in the same spot as a beard. It has been described as a ridge or cockscomb. You can see and feel the higher crest but it will not be fuzzy.

Iris with crests are less popular in gardens than iris with beards or iris lacking both a beard and crest. 

Iris crista showing the raised tissue known as a crest, iris identification
Iris crista showing the raised tissue known as a crest, photo by Dennis Kramb

Iris Identification

There are three main types of iris with rhizomes. Bearded iris have a beard. Crested iris have a crest. If your iris has neither a beard nor a crest it is a beardless iris.

Iris Identification by Bloom Time

Bloom time is not a very precise way to identify an iris type but it is a useful to confirm your identification in some cases.

Early Spring

An iris that blooms in early spring will bloom along with snowdrops, and glory of the snow. Flowers appear as the snow is melting and before other common spring bulbs like tulips and daffodils. If your iris blooms this early it is a reticulata type.

Late Spring

In late spring tulips and peonies are flowering and this is the time when the bearded iris type flowers. Very short bearded iris will flower earlier, before peonies, and the taller bearded iris flower at about the same time as peonies.

Recent breeding of bearded iris has produced cultivars that are repeat bloomers. This means that they can bloom at various times of the year, including late fall. But late spring is their main bloom time.

Summer

Once the bearded iris are finished blooming it is time for the summer iris. The  Dutch type usually flower first, followed by several different species of beardless types. If you grow several different beardless types you can compare their flowering time and use this information to identify the species. But if you only have one of the summer flowering types it is difficult to identify them.

Growing of Iris

Iris are generally easy plants to grow in the garden and most of them take very little maintenance work. Except for the iris borer, pests are not a big concern. With careful selection you can have iris blooming from early spring to mid summer.

In future posts I will have a look at each type of iris and help you select and take care of your iris.

References:

  1. Photo source for iris rhizome; Rhian
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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

47 thoughts on “Iris Identification – Which Type of Iris Do I Have?”

  1. Great information. I’m glad i found this page. i live in Florida. This page has made me realize that there are many gorgeous irises that i do not have. Thank you.
    Kaffee

    Reply
  2. Will Arils fall under the ‘bulb’ category to help Iris identification? I have seen pictures that appear to be bulbs and tuberous roots. I’ve read Arils are not classified as ‘bearded’ because their ‘beards’ are not developed. Can you please shed light?

    Reply
  3. May I ask please what the name of the historical looking iris is the above photo in this post? The one with the text that reads, “Bearded iris with white standard petals and purple falls petals.”
    Thank you.

    Reply
  4. We had a beautiful tall purple iris at my old house that grew in a circle. I’d love to buy it again, but don’t know what it was called.

    Reply
  5. I would like to send you a pic of an Iris to find out what kind it is. I live in Central and it is blooming 2nd week of May but no beard. And it has bulbs. It’s yellow falls and white stands.

    Reply
  6. Yesterday a friend gave me a large clump of out-of-bloom iris. She stated that they had bright yellow flowers but she didn’t know what type of iris it was. When dividing the clump today I observed that the rhizomes are pink in color while the roots are white. The rhizomes on this mature clump were not as fat as those I’ve seen on bearded iris. The leaves are narrower than the usual bearded iris too. Does this sound like it might be a Siberian Iris?

    Reply
  7. Out my Iris garden a ‘new’ flower has just emerged. It is a single stem about 4 1/2 feet high. The leaves are narrower than the regular iris leaves but 1 1/2 feet taller that the other iris leaves. The stem hosts multiple flowers near the top but not the bearded form as the regular iris. Any idea what this is? I would attach a photo if I understood how to do that.

    Reply
  8. I have an Iris-like plant, very flat, thin and fan-shaped; grows via rhizomes, giving out new shoots. Initially, I thought it was I. pallida, but it’s not. What do I have? Thanks much

    MDFortes (migueldfortes@gmail.com)

    Reply
  9. Am surprised you did not mention Iris domestica (common name Blackberry Lily), particularly given substantial interest in natives. I’m just an amateur, so maybe others you admitted? Its leaves are similar to germanica, but not a rhizome which are a pain. The orange flowers are diminutive by comparison to other varieties, but with strong foliage is not bad for a care-free plant.

    Reply
  10. At the “Iris Identification by Bloom Time”, you haven’t mentioned the crested Iris. can you please tell us at what time does it bloom ?

    Reply

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