How to Grow Irises in Your Garden: 7 Iris Care Tips

Irises are colorful, many-petaled flowers that grow from bulbs or rhizomes. Most breeds of iris have three or four soft inner petals surrounded by sturdier outer petals called “falls.” Around 300 species of iris flowers exist and each breed of iris has its own specific characteristics and optimal growth conditions.

Irises can either be bearded and crested. Bearded irises have soft, hairy fuzz along their falls and crested irises have a ridge or comb on the center of their falls. Most species of iris are drought tolerant and will attract pollinators like hummingbirds and bees to your garden.

Iris plants come in two main forms: iris bulbs, which grow from bulbs, and iris rhizomes, which grow from rhizomes. Here is a little more information about both.

• Iris rhizomes: Iris rhizomes grow from a horizontal plant stem that grows horizontally underground and sprouts new plants from nodes on its surface called a rhizome. The rhizome’s main purpose is to store carbohydrates and proteins so the rhizomatous plant can survive between growing seasons. Rhizomatous irises usually bloom in late summer.
• Iris bulbs: Bulbs have swollen underground stems where new bulbs grow from the base of the original bulb. Bulbous irises are smaller in size and bloom smaller flowers than rhizomatous irises. Depending on the climate, bulbous irises typically flower in early spring.

Within those two types are more specific cultivars of iris varieties:

1. 1. Bearded iris (Iris germanica): The most popular type of iris is the rhizomatous Iris germanica which grows about two to three feet in height, has sword-like leaves, and fuzzy inner petals. They grow as both dwarf and tall bearded varieties and come in a variety of different colors.
2. 2. Siberian iris (Iris sibirica): The Siberian iris grows from a rhizome and is a beardless iris. It is an ornamental plant native to Europe and Central Asia. These irises bloom in the late spring to early summer, sprouting three large outer falls that surround inner petals, ranging in violet-blue to white, with grass-like green leaves.
3. 3. Japanese iris (Iris ensata): The Japanese iris is a beardless, rhizomatous flower that can grow up to four feet in height. They are native to countries like Japan and Russia, and need consistently moist soil to thrive.
4. 4. Louisiana iris: Louisiana irises are rhizomatous hybrids that are native to North America which grow wildly in bogs, swamps, and ditches. They bloom in yellow, blue, pink, and white. They sprout just below the soil level in high-moisture regions like Louisiana, Arkansas, and Mississippi.
5. 5. Yellow flag iris (Iris pseudacorus): This rhizomatous breed of iris is native to Europe, Africa, and Asia, thriving in wet areas like riverbeds and streams. They self-seed and grow at a rapid rate. They have bright yellow flower petals and long, grass-like leaves.
6. 6. Dutch iris (Iris hollandica): This bulb-grown hybrid iris is a cross between the Spanish iris and the Moroccan iris. These plants can grow up to two feet high and have long, narrow green leaves. They bloom in colors like blue, white, and yellow.
7. 7. Dwarf iris (Iris reticulata): The dwarf iris is a bulb-grown, bearded flower that sheds its leaves after blooming and goes dormant in the summer. These plants grow to about four to six inches in height, making them much smaller than the standard iris. Their petals come in blue, yellow, and purple.
8. 8. Dwarf crested iris (Iris cristata): A crested iris is an iris that has a hairless, raised crest down the center of its falls. These flowers are native to the eastern part of the United States and grow to about six inches in height. They grow in a range of colors from lavender to blue.

Irises that grow from bulbs are generally planted in the fall, whereas rhizomes can be planted in the late summer to early fall—though the exact time may vary depending on the specific cultivar (and warmer climates may allow for a later growing season). Iris plants can also be grown from seed at the same time however, their bloom times will be delayed until the next year. Nighttime temperatures should remain at or above 40 degrees Fahrenheit. Irises thrive best in USDA hardiness zones 3–9.

Irises are relatively simple to grow and are generally low maintenance. Here is a guide on how to grow the common bearded iris:

1. 1. Pick your spot. Some irises thrive in full sun, while others require partial shade. Depending on what kind of iris you are growing, choose a spot that caters to the needs of your plant. Keep in mind that your irises will die in the winter if you live in a climate that drops below 40 degrees Fahrenheit.
2. 2. Prepare your soil. Use a tool to loosen your garden soil at least 10–15 inches deep and ensure it has good drainage. Add compost or organic matter to your soil to make your soil slightly acidic with a pH of around 6.8–7.0.
3. 3. Plant your irises. Irises can be grown from seeds or bare-root rhizomes. You can obtain iris seeds at your local nursery or harvest them from seed pods. If you’re working with seeds, plant your iris seeds anywhere from a half to three-quarters of an inch below the soil surface, and at least two to five inches apart. To plant a bare-root iris rhizome, dig a shallow hole with a ridge down the center. Place the rhizome horizontally on top of the ridge, with the roots spread out down the sides of the mound. Fill in the hole around the rhizome, leaving some of the top end and foliage exposed. You can plant one rhizome by itself, or in groups of three, with each of the rhizomes 12–24 inches apart.

Here are some tips for taking good care of your irises.

1. 1. Water your irises thoroughly. Most irises require regular watering, but if you water them too much they may develop rhizome rot. Avoid mulching your irises because mulch may cause your bloom to retain too much moisture.
2. 2. Provide enough sunlight. Irises can do well in full sun or partial shade, as long as they get at least six hours of sunlight per day.
3. 3. Fertilize. You can use an all-purpose fertilizer in the early spring, avoiding high-nitrogen fertilizer because this may make your plant more susceptible to disease.
4. 4. Keep your rhizomes exposed. Unlike bulbs, rhizomes need to have a small part of them exposed at all times. The sun and elements will help keep the rhizome dry so that it does not rot beneath the soil surface.
5. 5. Eliminate pests. Irises are vulnerable to iris borers, a type of moth larvae, which create vertical lines on the iris leaves. They’re also susceptible to aphids, slugs, iris weevils, caterpillars, whiteflies, and thrips. You can eliminate most iris pests by using your hand to pick them off or blasting your plants with the garden hose.
6. 6. Deadhead your irises. Irises should be deadheaded after the blooms are spent to prevent uncontrolled pollination.
7. 7. Divide your rhizomes. Every couple of years, dig up your rhizomes and break them apart, removing the older or softer rhizomes. Rinse off the soil from the roots and trim the leaves, then replant the rhizome in a new location.

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