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Forty Facts About Irises: Beautiful Flowers and Useful Plants

Linda Crampton is a writer and former science teacher with an honors degree in biology. She enjoys writing about science and nature.

Irises growing in a botanical garden

Irises growing in a botanical garden

The Beauty of Irises

Irises are beautiful and often showy flowers. They are a wonderful attraction that I find very hard to resist. I often feel compelled to stop and admire the flowers whenever I see them in a garden or a landscaped area.

Irises are sometimes useful as well as attractive. The rhizomes of some species are known as orris roots. These are used commercially to produce a pleasant fragrance for perfumes and for items such as potpourris and natural toothpastes. Orris root is also used to flavour beverages and food. One species of iris—the yellow flag—is used as a water purifier. Unfortunately, this species can become invasive.

Irises generally bloom in late spring and early summer. Some produce flowers for a second time in late summer. The leaves of an iris plant are generally tall, narrow, and sword-shaped. Irises are perennial plants and grow from rhizomes or bulbs, depending on the species. I've described forty facts about the plants below.

Irises growing in a landscaped area at a shopping centre

Irises growing in a landscaped area at a shopping centre

Facts About the Flowers

1. Irises are named after Iris, the goddess of the rainbow in Ancient Greek mythology.

2. The flowers come in all the colours of the spectrum, except for red. Some irises have a dark, red-brown colour, but there are no irises that are bright red.

3. Iris flowers have six attractive and colourful lobes. The three inner lobes are petals and the three outer ones are sepals.

4. Most flowers have coloured petals and smaller, green sepals. When the petals and sepals are both large and colourful, as in iris flowers, they are sometimes known as tepals.

5. The three petals of an iris flower stand upright and are often referred to as standards.

6. The three sepals may also stand upright, but they more commonly spread outwards or curve downwards. The sepals are also known as falls.

7. The fruit of iris flowers takes the form of a pod. The pod contains the seeds.

Types of Iris Flowers

8. Irises belong to the flowering plant family known as the Iridaceae and are classified in the genus Iris. The genus is the first word in the scientific name and the species is the second.

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9. A huge variety of cultivated irises have been created. In some flowers, the standards and the falls have different colours. The falls are sometimes patterned or ruffled, which often adds to the attractiveness of the flowers.

10. According to the American Iris Society, cultivated irises are divided into three groups: bearded, aril, and beardless.

11. Bearded irises have hairs running the centre of their falls. Beardless ones lack these hairs, as their name suggests. Aril irises are named for the white cup or collar (the aril) around their seeds. Hybrids between aril and beaded irises are called aribreds.

12. Irises are also classified into rhizome and bulb types. A rhizome is a horizontal underground stem. It has nodes that produce roots and a shoot. A bulb is a compact and highly modified stem. It has leaves (although they aren't green) and produces roots and a shoot when activated.

Even though the imported garden irises are very beautiful, the 28 iris species native to the United States are beautiful in their own right.

— USDA Forest Service

The Yellow Flag Iris

13. The yellow flag iris, or yellow flag, has the scientific name Iris pseudacorus. It's a beautifuł plant with yellow flowers. The sepals are often decorated with short brown or purple streaks.

14. Yellow flag is native to Europe, Asia, and North Africa. It has been introduced to North America.

15. The plant grows at the edge of ponds and lakes in wet soil and shallow water. It may be as tall as five feet, although most plants are closer to three feet in height.

16. Yellow flags form dense stands above ground and thick mats of rhizomes in the soil. Since rhizomes are stems, they branch and produce shoots. They also develop roots. Very often, the yellow flags in an area are produced by the same rhizome system and are connected to each other, forming a colony.

17. The seeds of yellow flag iris were once roasted and used to make a beverage. The plant is toxic, however. Ingestion can cause vomiting and diarrhea. The flowers were once used to make a yellow dye, and the rhizomes were used to make a black one. Contact with the leaves or rhizomes can irritate the skin.

A yellow flag iris in John Hendry Park, Vancouver

A yellow flag iris in John Hendry Park, Vancouver

Beautiful and Often Invasive Pests

18. Despite the plant's acknowledged beauty, the Invasive Plant Council of British Columbia (where I live) says that the yellow flag is "wickedly aggressive" and shouldn't be planted. The plant isn't classified as invasive in all parts of North America, however.

19. Yellow flag colonies may consist of hundreds of plants. The irises can crowd out the native plants needed by birds and wildlife. They can also block drainage and irrigation channels. In addition, their rhizome mat can trap sediments and change the nature of habitats.

20. The plant spreads easily. A piece of broken rhizome that is carried to a new area by water can grow roots and shoots and start another colony. Seed pods and seeds float and can be transported to new areas by flowing water.

This fast-growing and fast-spreading invasive plant can outcompete other riparian (water loving) plants, forming almost impenetrable thickets.

— Okanagan and Similkameen Invasive Species Society

Yellow flags growing beside Trout Lake in Vancouver

Yellow flags growing beside Trout Lake in Vancouver

Orris Root Fragrance and Flavour

21. Three types of irises are used to produce orris roots commercially. These include the species Iris germanica (German iris) and Iris pallida as well as the variety known as Iris 'florentina'.

22. The word "orris" is thought to be a corruption of iris.

23. Technically, orris roots are rhizomes, not roots. The preserved rhizomes are brown in colour and have a woody and sometimes lumpy appearance.

24. Orris root has a scent that resembles the fragrance of violets. The root must be dried for at least three years in order to develop the best scent, however.

25. The aged root is ground into a powder and then steam distilled to obtain an essential oil. Sometimes the thick oil is known as orris butter.

26. Orris oil is added to perfumes, cosmetics, and some types of gin, including Bombay Saphire. In perfumes, it provides a base note in the fragrance. It also acts as a fixative that prevents other scents from disappearing.

27. Like many other natural products from plants, orris root is said to have a long list of health benefits. These benefits haven't been scientifically proven, however.

A multicoloured iris

A multicoloured iris

Orris Root Allergy

28. Prolonged exposure to orris root or its components may irritate the skin and airways.

29. Some people develop an allergic reaction when they are exposed to orris root.

30. An allergic response is a more serious disorder than an irritation and involves the release of histamine in the body.

31. Symptoms of an orris root allergy include hay fever, asthma, and hives.

32. Hypoallergenic products don't contain orris root.

Iris Toxicity

33. Irises are mildly to moderately poisonous for humans and animals. The poisoning is generally not fatal. It's important to note that different individuals have different sensitivities to noxious chemicals and that effects may depend on the amount and part of the plant that's eaten.

34. ASPCA (American Society for the Prevention of Cruelty to Animals) says that irises are poisonous for both dogs and cats. The organization also says that the rhizomes are the most toxic part of the plant.

35. Like yellow flag, all irises can cause salivation, vomiting, and diarrhea. Skin contact with any part of an iris plant can cause dermatitis.

36. The toxin in irises is called iridin.

37. Preserved orris root seems to be safe for humans in the small quantities used as a fragrance or flavouring, but the fresh parts of the plant definitely aren't.

Fleurs-de-lis at the bottom of the tomb of Robert FitzElys in St. Mary the Virgin Parish Church, Waterperry, Oxfordshire; the fleurs-de-lis are the red drawings on the right of the tomb

Fleurs-de-lis at the bottom of the tomb of Robert FitzElys in St. Mary the Virgin Parish Church, Waterperry, Oxfordshire; the fleurs-de-lis are the red drawings on the right of the tomb

The Fleur-de-Lis: Perhaps a Stylized Iris

38. Fleur-de-lis is a French term that refers to a stylized drawing of a flower. The drawing is associated with royalty and heraldry. It has also been used to represent the Virgin Mary.

39. Although the term fleur-de-lis means "flower of the lily" when translated into English, the drawing actually looks like an iris with its upright standards and drooping falls.

40. It has often been suggested that the word lis (or lys, as is sometimes used) is actually a corruption of a word associated with either the yellow flag iris or its habitat. There are different theories about what this word was, however. The yellow flag is thought to have been abundant in the wetlands of France at the time when the fleur-de-lis symbol first appeared.

A Lovely and Interesting Plant

Irises are said to be easy to grow. I remember that we had lovely ones in our garden when I was a child. Whether they are enjoyed in a garden or in parks, the flowers are a wonderful sight. I wish the blooming period lasted for longer, though. If the reblooming species are planted, the enjoyment in seeing the flowers can be experienced for a second time later in the summer. I think that's definitely something to look forward to.


  • Iris information from the Royal Botanic Garden
  • Classification of the flowers from The American Iris Society
  • Facts about native irises from the United States Department of Agriculture (USDA) Forest Service
  • Yellow flag iris facts from the Invasive Species Council of British Columbia (ISCBC)
  • Information about the yellow flag iris from the Okanagan and Similkameen Invasive Species Society (Oasiss)
  • Orris facts from WebMD
  • Information about the fleur-de-lis from the Getty Museum

Questions & Answers

Question: Why don't my irises flower?

Answer: There are multiple reasons why irises don’t flower. I’ll list some possibilities. An expert who sees your plants and their environment and asks you questions would be able to give you more specific advice.

Irises may fail to flower due to soil problems, such as too much or too little fertilizer in the soil or too much or too little water. The presence of pests in the underground parts of the flowers may prevent flowering. Planting these parts too deep in the soil can also prevent flowering, as can overcrowding. Environmental problems such as too much shade or a period of very low temperatures once leaves and buds have appeared can stop plants from blooming as well.

Question: I have bearded iris pods. Can I plant them and expect new plants to germinate? Do I have to dry the pod and then extract the seeds and then plant them, and when do I plant?

Answer: The seeds should germinate if planted correctly, but they do need to be removed from the pod. They should be collected once the pods have dried, turned brown, and started to open up. The seeds inside should no longer be green. If they need to be stored before being planted, they can be kept in an envelope.

Most iris seeds need to be exposed to cold to germinate. They could be planted outdoors in the fall or early winter. If this is done, they should be placed about an inch apart and a half inch to three-quarters of an inch deep in the soil. The soil should be kept moist but not wet. The seeds could be planted in a pot that is left outside instead of in the ground.

Some people recommend soaking the seeds before planting them to get a higher germination rate. Soaking is done for forty-eight hours to two weeks. The water must be changed daily. A strainer is useful to prevent the loss of seeds when the water is changed.

Although the steps described above work in many areas, you should consult a garden center or expert iris growers in your part of the world before you plant the seeds. The local environmental conditions over winter might mean that the steps need to be modified, such as by exposing the seeds to a cold period in a refrigerator instead of outdoors.

Question: What do I need to do to get my iris to bloom twice?

Answer: The rebloomers are interesting types of irises. Some kinds produce new flowers soon after the old ones die and others produce new flowers later in the season. Even though plants are bred as rebloomers, they may not produce a second set of flowers in a year, however. The ability depends on environmental conditions as well as genetics. Though I don't know the specific problem that is stopping your plant from reblooming, I can describe some reasons why irises fail to rebloom.

Many rebloomers won’t produce a second crop of flowers in the more northerly and cooler zones of the United States. It’s important to buy a variety that can rebloom in these conditions if this is where you live. If the nights are consistently warm the plants may not rebloom either, depending on the variety. Some types need a cooling period in order to produce more than one set of flowers.

The plants need extra care in terms of water and fertilizer to enable them to produce two or more sets of flowers in a year. They likely won’t rebloom in their first year of life but may when they are two or more years old. The rhizomes will probably need to be divided and replanted more often than those of irises that aren’t bred to rebloom.

Question: My blue iris has white streak damage in the leaves. Why?

Answer: You really need to consult a plant care specialist in your area who can examine the plant or at least look at photos of the damage and ask you questions. The streaks may have appeared due to an infection of some kind, so you should get the iris checked by a local expert.

© 2015 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on September 28, 2017:

Thanks for sharing the information, Barbara. Your neighbour must have been very upset about the ruined iris bed!

Barbara Radisavljevic from Paso Robles, CA on September 28, 2017:

This iris just may be my favorite flower. It is drought-resistant, easy-to-grow, and I love the smell. As far as I know, the rhizomes are not toxic to gophers. They demolished a whole bed of my neighbor's irises.

Linda Crampton (author) from British Columbia, Canada on September 28, 2017:

Hi, Linda. I appreciate your visit and comment. Irises are one of my favourite flowers, too. There are so many different varieties and they are so lovely.

Linda Jo Martin from Post Falls, Idaho, USA on September 28, 2017:

I love this! Irises are one of my favorite flowers. People with too many could always give them to me... back when I had land to live on. I'm in an apartment now.

Linda Crampton (author) from British Columbia, Canada on March 22, 2016:

Thank you very much for the comment, ChitrangadaSharan!

Chitrangada Sharan from New Delhi, India on March 22, 2016:

These are such beautiful flowers and their colours are so unique and bright. I loved going through the interesting facts about Irises , the pictures and the video.

Thanks for sharing this informative and interesting hub!

Linda Crampton (author) from British Columbia, Canada on March 21, 2016:

Hi, Peggy. I like all the irises that I've seen. They are such beautiful flowers. Thanks for the share!

Peggy Woods from Houston, Texas on March 21, 2016:

Great information about the iris plants. I personally like the bearded varieties grown up north although the Louisiana irises more common in our area certainly are also beautiful. Sharing!

Linda Crampton (author) from British Columbia, Canada on October 01, 2015:

I agree - the different colours of iris flowers are gorgeous! Thank you very much for the visit, Kailua-KonaGirl.

KonaGirl from New York on October 01, 2015:

I love the beautiful, exotic look of irises and am always amazed at the gorgeous variety of colors. Every time I see I new color I wish I had the space to add another variety.

Learn some things from all these facts such as didn't know that the Yellow Flag variety are so invassive. Good to know for my small gardening space.

Linda Crampton (author) from British Columbia, Canada on September 02, 2015:

Thank you very much, adevwriting!

Arun Dev from United Countries of the World on September 02, 2015:

Congrats on the Most Beautiful Hub award!

Linda Crampton (author) from British Columbia, Canada on September 02, 2015:

Thank you for such a kind comment, Pamela! I appreciate it very much.

Pamela Oglesby from Sunny Florida on September 02, 2015:

It is obvious why you won the award. I have always loved Irises, and I miss seeing them in FL. Your article had a wealth of information, and it brought back memories of the irises I enjoyed when I was growing up and lived in the north. Beautiful hub.

Linda Crampton (author) from British Columbia, Canada on September 02, 2015:

I appreciate your kind comment very much, MsDora. Congratulations on your Hubbie award!

Linda Crampton (author) from British Columbia, Canada on September 02, 2015:

Thank you so much, Bill. I was very happy to see that you won a Hubbie award, too!

Dora Weithers from The Caribbean on September 02, 2015:

Congratulations on winning the Most Beautiful Award! Keep on sharing such interesting information and beauty.

Bill De Giulio from Massachusetts on September 02, 2015:

Congratulations Linda. This hub is both educational and beautiful. Certainly well deserved.

Linda Crampton (author) from British Columbia, Canada on September 01, 2015:

Thank you very much, Faith! Congratulations to you for your Hubbie award, too!

Faith Reaper from southern USA on September 01, 2015: