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 proper 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.
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 farther from the truth. There are many different types of iris and in my opinion, some of the others are a better choice for the garden.
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.
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 shallower than that.
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 midsummer 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.
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.
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.
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 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 flowers 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 midsummer.
In future posts I will have a look at each type of iris and help you select and take care of your iris.
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?
Siberian rhizomes are not very distinct. It might be Iris pseudacorus, which can spread a lot in the right place.
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.
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)
try posting a picture of the flower here: https://www.gardenfundamentals.com/facebook-group/
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.
A few years ago it was not an Iris – name got changed.
There are thousands of iris.
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 ?
I have some iris bulbs that I dug up from an empty lot. They are dark purple, and they multiply more than any other iris bulbs that I have. If I put 2 or 3 in the ground, the next year it’s a large clump of iris. I wonder why my other iris bulbs don’t multiply like that.
Genetics – we don’t all grow the same – neither do iris.
My yellow irises look normal in every respect except they always have ugly withered brown appendages growing just below the main blossom or further down the stem. I cannot find any information which speaks such a phenomenon. They are gone already this summer so I haven’t any photo to post.
That’s called the spathe that protects the emerging buds. Search for “parts of bearded iris” to learn more. After blooming, cut the flower stem down to where it emerges from a low leaf and your spathes will be gone.
Thanks that helps. I now know I have a Iris which grows from a Rhizome, blooms in the summer, has purple falls and yellow to white standards.
Very informative post. Thank you for it 🙂 I don’t have a garden of my own (yet) as I live in an apartment but I admire flowers a lot & this is the time of the year when bearded iris are in full bloom. Your post made it easier for me to distinguish the various varieties.
I have a German bearded iris that was sent to me by accident. I normally keep photos and catalog all of my iris. But I cannot identify this one. It blooms mid-late season. Beards and style arms are old gold. It is a magenta self, with white streaks on shoulders, and small red patch on the hafts. Is there a way I can send you a photo?
Consider posting the question on our Facebook Group: https://www.facebook.com/groups/GardenFundamentals/
We have an iris expert there.