How to Grow Irises – Guide to Planting, Care and Pruning Iris

Learn how to grow irises with our handy guide. This popular flowering plant is an early spring bloomer, which is easy to care for.

Irises have showy flowers and are popular in cottage gardens. They come in many colors, shapes, and sizes.

They are deer-resistant and attractive to both birds and butterflies. With more than 250 species to choose from, there is sure to be one that will look great in your garden.

Keep reading to learn about growing iris plants.

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Iris overview

Below is a list of plant details for irises

• Family: Iridaceae
• Genus: Iris spp.
• Botanical name: Iris. Varieties in the genus have their own botanical names (e.g.  Iris germanica, Iris sibirica, Iris pseudacorus, Iris reticulata, and Iris ensata).
• Popular types of irises: German, Siberian, yellow flag, dwarf, Japanese, and bearded.
• Native to: Regions in the Northern Hemisphere with temperate climates, notably Europe, Asia, North Africa, and North America.
• Grows from: Mainly from rhizomes but some species grow from bulbs.
• Type of plant: Perennial
• Size: Depends on the cultivar. Sizes range from 6-12 inches (15 to 30 cm) for dwarf irises and up to 48 inches (120 cm) tall for some bearded irises, Japanese irises, and yellow flag irises.
• Hardiness zones: Cold hardy in zones 3-9.
• Toxicity: The ASPCA considers iris toxic to dogs, cats, and horses, particularly the rhizomes. It is mildly toxic to humans.

How to grow irises

Even though there are many sizes, colors, and bloom times for irises, their overall care is similar. Irises are easy to grow if you keep a few basics in mind.

Irises thrive in full sun and will also grow in partial shade. They prefer at least 6 hours of sunlight each day.

Bearded irises, in particular, do best in full sun. Siberian irises and Japanese irises are more adaptable to partial shade.

Proper sunlight helps irises grow strong, and produce a lot of flowers. If the stems of your irises become leggy and prone to falling over it’s a sign that they need more sunlight.

Soil and watering needs of irises

Irises prefer well-draining soil with a pH of around 6.0-7.0 (slightly acidic to neutral). Adding compost or other organic matter before planting will improve drainage.

Plant rhizomes with the tops exposed just above the soil surface. This helps to prevent rot.

Growing irises in pots can be a challenge because you’ll need a lot of room for the rhizomes and their roots. Planting directly in the ground is more successful.

Once established, irises can be quite drought-tolerant. However, they prefer consistent moisture, especially during the growing season.

Water your iris plants regularly from the base. Watering from above makes the foliage wet which can lead to fungal diseases.

Fertilizing needs for irises

Feed with a low-nitrogen fertilizer in early spring. Too much nitrogen can promote excessive foliage growth but results in fewer flowers.

I like to fertilize about 6-8 weeks before bloom time. If you have reblooming types of iris, be sure to give them a light feeding after the first blooms are finished.

Avoid fertilizing in the fall, since this could encourage new growth that might not harden off before winter.

Flowers of irises

Irises grow from both rhizomes and bulbs. Rhizomes produce larger flowers, including bearded flowers. Irises that grow from bulbs are smaller and more suited to rock gardens or the front of borders.

The flowers of irises are known for their beauty, shape, and colors. They typically have six petal-like structures (known as “falls”) and three inner petals (known as “standards”).

The falls often have a ruffled or fringed appearance.

Irises come in many colors including blue, purple, white, yellow, pink, red, and bi-colored variations. Some feature intricate patterns or markings on their petals.

Flower sizes range from small delicate blooms to large showy flowers.

Many irises have a beard. This is a fuzzy or hairy line running down the center of each fall. It often contrasts in color with the petals, making it a striking feature.

Irises generally bloom in late spring to early summer, depending on the type. Flowers typically last 1-2 weeks.

Pruning irises

After blooming, cut the stems to the ground level. This encourages the plant to send energy for new blooms rather than seed production.

When blooming has finished, in late summer or early fall, the foliage will start to die back. Cut back yellowing or brown leaves close to the base of the plant.

Be careful not to cut too close to the rhizomes. Leave healthy green foliage to feed the rhizomes for next year.

Once the foliage has died back completely (late fall or early winter) trim any remaining foliage to 6-8 inches from the ground.

Division of irises

Every 3-4 years, the clumps will become overcrowded. This will result in fewer blooms.

Dig up the rhizomes, and separate them. Keep the healthy rhizomes, but discard any old or diseased sections.

Replant the iris divisions, leaving plenty of space around them for future growth.

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Admin note: this post for perennial iris care first appeared on the blog in April 2013. I have updated the post to add all new photos, a printable project card with iris growing tips, and a video for you to enjoy.

Yield: A garden of iris perennials

How to Grow Irises - Guide to Planting, Care and Pruning Iris

Print

Irises come in many shapes, colors, and sizes. Once established, they are fairly drought-tolerant and easy to care for.

These care tips will help you get the most out of your iris plants.

Prep Time 30 minutes

Total Time 30 minutes

Difficulty easy

Estimated Cost $10

Materials

• Iris rhizomes or bulbs
• Compost or other organic matter
• Low-nitrogen plant fertilizer

Tools

• Watering can or hose

Instructions

1. Plant iris where they will get at least 6 hours of sunlight a day.
2. Rhizomes should be planted with the tops exposed above the soil, to help prevent rotting. Iris bulbs should be planted about 4 inches deep.
3. Add compost or other organic matter at planting time.
4. Water well. Once established, they tolerate lower levels of water.
5. Fertilize in early spring with a low-nitrogen plant fertilizer. Feed again about 6-8 weeks before bloom time. Feed rebloomers after flowering to encourage a second round of blooms.
6. Bloom time is spring through summer depending on type. The flowers come in many colors and include those with frills and beards.
7. Rhizome irises produce larger flowers than bulb irises.
8. Prune stems to the ground level after blooming. Leave the foliage until fall to feed the plant for next year.
9. In late fall, remove all dead foliage about 6 inches from the ground.
10. Every 3-4 years, dig up the rhizomes and remove dead or decaying ones. Replant healthy rhizomes, giving them plenty of room to spread.

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