Growing irises - planting & caring for irises - garden design (2023)

Irises are easy-to-grow perennials with elegant, colorful flowersBy Linda Hagen

With many different types and colors available, there is an iris for almost every garden. Named after the Greek goddess of the rainbow, irises bring color to the garden in spring and summer. The vast majority are hybrids, with the most popular being beingbartiris. Other popular varieties include Siberian and Japanese irises, Louisiana irises native to North America, and Dutch hybrids.

On this page: basics|Types of irises|Plant irises|Care|Iris Pictures|Design Tips

  • Types of irises


Photo by: Jeanne Provost/Shutterstock.


Varieties suitable for zones 3-9


Irises come in many different sizes, some are as little as six inches long and others can grow up to four feet.

  • Dwarf varieties 6 to 12 inches tall and wide
  • Dutch varieties 1-1/2 to 2 feet tall and 6 to 12 inches wide
  • Large bearded varieties range from 2 to 4 feet tall and 1-1/2 to 2 feet wide


Irises need full sun for at least half the day. Some cultivars tolerate partial shade such as Siberian irises and Pacific Coast natives (Iris innominate, Iris tenax, Iris macrosiphonAndIris douglasiana). Many irises will grow in total shade, but they most likely won't bloom.


Most irises bloom in spring or summer. Dwarf varieties tend to flower earlier in spring, medium-sized varieties flower later in spring, and larger bearded varieties flower in late spring and summer. Re-blooming strains will bloom once in summer and again in fall.


There is an extremely wide variety of colors, ranging from white to almost black; although most commonly in shades of lavender, purple, white, and yellow.


Irises are known to be poisonous to pets, with the bulb being the most poisonous part. See moreCommon poisonous plants for dogs and cats.

Types of irises

There are 2 main groups of irises: rhizomatous and bulbous. The bulbous irises flower in late spring, while the rhizomatous irises flower in summer.

Rhizomatous irises:

Grown from rhizomes (a type of bulb) and can be further divided into 3 categories:

  • Bearded:Irises are the most commonly grown and get their name from the distinctive "beard" of white or colored hairs in the middle of each fall (outer surrounding petals). Many cultivars produce multiple flowers per stem and come in a variety of colors.
  • Bartlos:Beardless irises include the Siberian, Japanese, Pacific, and Louisiana types, and all have smooth traps. Known for being very adaptable, Siberian irises are a good choice for low-maintenance mixed beds. Japanese and Louisiana strains do better in moist to wet soils, while Pacific Coast strains do best in milder climates with winter rains and drier summers.
  • Hood:Crested irises thrive in full sun or partial shade in moist, humus-rich soil.

bulbous irises:

This group includes the Dutch hybrids and the smaller netted or dwarf irises. They all shed their leaves after flowering and go into a dormant phase over the summer. Dutch hybrids tend to flower earlier than the tall bearded rhizome-like varieties and are the well-known variety used in spring bouquets by florists. Reticulated irises are good for growing in groups, but should be divided every two to three years to avoid overcrowding. They are also good forSteingärtenand bustle in pots.


(Video) Iris growing - how to choose, plant and grow irises

Photo von: Nadzeya Pakhomava / Shutterstock.

When to plant:

The best time to plant iris rhizomes or bulbs is late summer to early fall to give them ample time to take root before the growing season ends. In hotter climates, they can be planted in September or October.

Where to plant:

Choose a sunny location for your irises where they will not be exposed to standing water. Raised beds are ideal for growing irises as they provide the good drainage needed.

How to plant:

Prepare planting beds up to two weeks in advance by loosening the soil to a depth of 10-12 inches to establish good drainage. Organic material can also be mixed in at this time. Iris rhizomes should be planted where they are easily visible on the soil surface, or thinly covered in warmer climates. They can be over-fertilized with a low-nitrogen fertilizer (avoid high-nitrogen as it can cause rot). Make 2 rows in the bottom with a small ridge in between. Lay the rhizome on the comb, spreading the roots to both sides. Steve Schreiner of Schreiner's Iris Gardens in Oregon says, "There are two reasons irises don't flower: planted too deep or not enough sun." B. Dutch irises should be planted to a depth of 5 inches, with the pointed end up and the roots down, and a spacing of 6 bulbs per square foot.


Most irises prefer average to fertile, neutral to slightly acidic, well-drained soil. However, Japanese irises prefer lime-free soil.

For more information on planting bulbs, seeOnions 101: Planting and storing onions



Cut back the flower stalks after flowering but leave the foliage intact so it can continue to collect and store nutrients and energy that will be stored for the following season. Cut off the leaves at ground level after they turn yellow in fall; This reduces the possibility of overwintering diseases or pests.

Dividing Iris Rhizomes:

Rhizomatous species need to be divided every 3-5 years, typically just after flowering. A reduction in flowering or rhizomes being pushed out of the soil can be signs it's time to dig them up and divide them. If this is a dividing year, don't cut back the foliage - so you know where it is. Carefully dig up the rhizomes and divide them by pulling them apart with your hands. However, some may need to be cut with a knife. Healthy rhizomes are about ¾ to 1 inch in diameter, with good root structure and one to two leaf compartments. Older or unhealthy (soft, rotten, or hollow) rhizomes should be discarded. Wash the roots with water and inspect for diseases or pests, especially iris borers. Trim the leaves to 4 to 6 inches and replant as above, with the rhizome on a ridge and the roots fanned out. Water newly planted irises well.

Modifications & Fertilizer:

Apply a low-nitrogen fertilizer a month before flowering. Mulch should not be used on rhizomes or near the leaves as this can cause rot. For post-flowering varieties, apply a light fertilizer fertilization after the first bloom and water regularly during dry periods of summer for an enhanced fall second bloom.


Irises generally have low water requirements once established, but can use a little more water if they are unusually dry just before flowering. Louisiana, Siberian, and Japanese irises need more water than the bearded species.


Although irises can be grown from seed, they can take a few years to flower. Most often they are propagated by dividing the bulbs or rhizomes in late summer or early fall.

Diseases and pests:

Irises can be severely damaged by iris borersThripseif not controlled.white fliesSlugs, snails, aphids and nematodes can also be a nuisance. Deer rarely harm irises, but will occasionally bite off the flowers of crested species, although they usually spit them out and leave them behind. Irises can also be affected by bacterial leaf rot, root rot, leaf spot, rust and viruses.


Any part of the iris can cause severe discomfort if ingested. Gloves should be worn when handling iris plants, rhizomes or bulbs as the sap can cause skin irritation.


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Photo by: Garden World Images, Ltd / Alamy Stock Photo.

Iris„Beverly Sills“
Large bearded iris
Buy now on Amazon

Height/spread:2-1/2 to 3 feet tall, 1 to 2 feet wide
Exposure:full sun
heyday:Late spring to early summer

One of the most popular large irises, fast-growing and plentiful.

Photo by: Guentermanaus/Shutterstock.

Iris"Dark Challenger"
Large bearded iris

Height/spread:3 to 4 feet tall, 1 to 2 feet wide
Exposure:full sun
heyday:Late spring to early summer

Strong chocolate scent, large flowers up to 8 inches, can produce 8 to 12 buds per stem.

(Video) Iris Complete Guide: Where to Buy, How to Plant, Fertilizing, & After Care. Schreiner's Iris Order!

Photo by: Penny's Pastime Pics / Shutterstock.

Large bearded iris

Height:3 feet
Exposure:full sun
heyday:Mid to late spring
Color:dark purple

Velvety, almost black autumn leaves; tolerant of a variety of soils.

Foto von: Deep Green / Shutterstock.

Iris"Princess Caroline of Monaco"
Large bearded iris

Height/spread:3 feet high, 1 to 2 feet wide
Exposure:Full sun to part shade
Color:Shades of blue with bright orange beard on autumn leaves

A vigorous early to mid bloomer with 5-6 buds per stem.

Foto von: Stacy J Maddox / Shutterstock.

Tall bearded reblooming iris
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Height/spread:Foliage 16 to 18 inches, flower stalks to 30 inches
Exposure:full sun
heyday:June and August/September
Color:White with light yellow reflections in the middle.

Large, fragrant flowers; often cited as the most reliable rebloomer.

(Video) How To Plant & Care for Iris Flowers - Get Large Blooms and Avoid Pests etc

Foto von: Deep Green / Shutterstock.

Iris'Champagne Elegance'
Tall bearded reblooming iris
Buy now on Amazon

Height/spread:2 to 3 feet tall, 1 to 2 feet wide
Exposure:full sun
heyday:Late spring to early summer / late summer to early fall
Color:Pale white petals (middle), delicate apricot autumn leaves (outer petals).

Fragrant, profuse flowering producing up to 7 to 10 buds per stem.

Photo by: Elizabeth Foster/Shutterstock.

Iris"Caesar's Brother"
Siberian iris

Height/spread:3 to 4 feet tall, 2-1/2 to 3 feet wide
Exposure:Full sun to part shade

Very adaptable to almost all conditions.

Photo by: Sally Anderson Nature / Alamy Stock Photo.

Iris'ruffled velvet'
Siberian iris

Height:Foliage to 2-1/2 feet, flower stalks to 3 feet
Exposure:full sun
Color:Was set Lila

Plant in masses for spectacular effect, thrives in moist soil.

Photo by: Ole Schooner/Shutterstock.

Iris"Black Fighting Cock"
Buy now on Amazon

Height/spread:2 to 3 meters high and wide
Exposure:full sun
heyday:Early to mid summer
Color:Violet to almost black

Large flowers can be up to 6 inches in diameter.

(Video) How to Plant Iris Correctly for Long Term Success

Photo by: Garden World Images Ltd / Alamy Stock Photo.

The Rainbow'bunt'
Japanese iris

Height:Foliage to 2 feet tall, flowers slightly larger
Exposure:Full to partial sun
heyday:Early to mid summer

Also called Japanese Water Iris, slightly later flowering, varieties available in shades of blue, lavender, pink and white.

Foto: Randy Lewis / Shutterstock.


Height/spread:6 to 9 inches high, 6 to 12 inches wide
Exposure:Full sun to part shade
Color:Pale blue with yellow crowned autumn leaves

Quick spreader, very short-stemmed flowers, suitable for rock gardens or rocky slopes. Protect from snails and snails.


With the variety of colors and sizes, there is the right iris for every garden area:

  • Iris flowers make spectacular additions to perennial borders.
  • Plant taller varieties with shrubs or in the back of perennial borders and low to medium-growing varieties in the middle of the border.
  • Irises provide a nice contrastdecorative sageAndpeonies, but keep the irises from getting crowded by neighbors.
  • Siberian and Japanese irises remain attractive throughout the summer and gracefully complement poolside planting.
  • Mix multiple varieties for spring through fall flowering.
  • Irises make excellent cut flowers and are best trimmed when the top flower is just beginning to open. Vase longevity is affected by temperature, with a maximum vase life of around a week.
  • To keep multiflowered irises looking pretty, they can be trimmed from top to bottom as the flowers open and fade.
  • Plant irises where you can watch and enjoy the butterflies and hummingbirds they will attract.
  • Good drought-tolerant companions are: daylily,coneflower,Lavender,sedum, blanket flower,black-eyed SusanneAndPhlox.

Buy iris plants on Amazon

Last updated: September 12, 2018

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