With over 200 species in this diverse group of plants, there is bound to be the perfect iris among them for your garden. In general, irises are low-maintenance and easy to grow. Their flowers come almost every color and bloom times vary depending on the species; some irises bloom in spring or summer, while others bloom in spring and again in fall.
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All species of iris boast flowers that are intricate and detailed. The three lower, drooping petals are commonly referred to as the falls. The three upright petals are called the standards. All parts of an iris blossom are colorful and can have a variety of patterns. Bearded irises are especially noteworthy for being available in a rainbow of colors and forms. The foliage of irises can also be quite striking, with long, lance-shape leaves in an attractive gray-green color. Even when not in bloom, the upright foliage can add interesting texture to a garden.
Iris Care Must-Knows
Bearded and bulb-type irises need well-drained soil to thrive because they will rot easily in soggy conditions. Many of these species are native to rocky mountainsides where there is sharp drainage. If you are looking for a species to grow in moist soil, look for a Louisiana iris, Japanese iris, or a yellow flag iris. Because different irises need such different growing conditions, make sure to do a little research before planting so you can provide your particular iris with what it needs.
When it comes to sunlight, all irises need 6-8 hours of full sun for the best blossoms and foliage growth. In too much shade, growth may be more stretched and prone to flopping over, and the plants will be less likely to bloom.
Related: 4 Rarely Shared Facts About Irises
Bearded irises and other rhizomatous types will eventually need to be divided every 2-5 years. If it has been quite some time since their last division and your irises seem to be flowering less and less, chances are it's time for them to be divided. The best time to divide and replant most irises is late summer to early fall. At this point in their life cycle, irises are somewhat dormant and are resting up for their fall growth cycle to begin.
To divide your irises, carefully lift the plants out of the ground (a pitchfork works great for this), and carefully tease apart the individual rhizomes. Don't worry if you break a few roots or rhizomes, as they are pretty tough plants. If there is some fairly large foliage attached to the rhizome, you can cut it back by half (this helps the plant lose less water while recovering from all the dividing upheaval).
Once they are all separated, you can replant by digging a small trench and setting each rhizome on a small mound of soil, then fanning out the roots around it. Then, backfill with soil around the rhizome, making sure to tamp down any air pockets and bringing the soil level just to the top of the rhizome. Water your plants well. Give them a good drink once or twice a week for the first several weeks after planting until the new roots begin to grow.
Irises are fairly pest-free, but iris borers are their one nemesis. This bug does most of its damage around blossom time, often between mid-April and mid-June. They chew their way into the leaves and then burrow down into the rhizome, leaving behind a trail of frass, a powdery brown residue. Once at their destination, the borers can eat several rhizomes and make their way through an entire bed. Their damage also opens plants up to infection from bacterial rot, too. These insects are tricky to control as they are often hidden within the plant where pesticide sprays can't reach them. If you do find a damaged plant, dig it up and see if you can locate the culprits and dispose of them. The best method of control is often prevention, so make sure to clean up any debris around your irises in fall and early spring, which is where borers overwinter.
More Varieties of Iris
'Bennerup Blue' Siberian Iris
Iris sibirica 'Bennerup Blue' produces cobalt-blue flowers with small white blotches. It grows 2 feet tall. Zones 3-9.
'Electric Rays' Iris
Iris ensata 'Electric Rays' is a Japanese iris with large double violet flowers streaked with white. This award-winning variety grows 3 feet tall. Zones 5-9.
'Caesar's Brother' Siberian iris
This variety of Iris sibirica is a classic Siberian iris with stunning deep purple blooms. Zones 3-8
'Champagne Elegance' Iris
This Iris selection has glamorous fragrant flowers, several per stem, that have pale buff-apricot falls with amber beards and white standards faintly blushed pink. This tall bearded type may rebloom in late summer. It grows 3 feet tall. Zones 4-9.
Iris chrysographes is known for its especially dark purple-red fragrant flowers. It blooms in early summer and grows 2 feet tall. Zones 7-9.
Iris forrestii, a striking yellow Siberian iris, grows about 16 inches tall and has mildly fragrant flowers. It blooms best when given some afternoon shade. Zones 4-9.
Iris cristata is a wild form native to areas of North America. It bears blue, white, or purple flowers in spring over tiny clumps of sword-shape foliage and grows to 1 foot tall. Zones 3-9.
'Satozakura' Japanese Iris
This Iris ensata variety prefers to grow in water or damp places where soil is acidic. Its large, somewhat flat mauve to rosy-pink flowers are yellow at the throat and conspicuously veined. Clumps grow to 3 feet tall. Zones 6-9.
This selection of Iris is a tall bearded type that offers pure-white flowers. It commonly reblooms in fall and grows 3 feet tall. Zones 4-9.
'Harpswell Snowburst' Siberian Iris
This Iris sibirica cultivar offers blue-violet flowers edged in white. It grows 3 feet tall. Zones 3-9.
Iris danfordiae is an early-blooming bulb with single yellow flowers in late winter. It grows 6 inches tall. Zones 5-8.
Iris pallida 'Variegata' A lovely variegated bearded iris with rich purple blooms and a pleasant fragrance. Zones 4-7.
Iris fulva has 4-inch-wide coppery-red flowers that are yellow at the center but without beards. The swordlike leaves may reach 4 feet tall. Zones 4-9.
'White Swirl' Siberian Iris
This variety of Iris sibirica makes tough clumps of narrow green sword-shape leaves. In midsummer, each stem blooms with several 1- to 2-inch pure-white flowers touched with yellow at the base. Zones 3-9.
Iris Companion Plants
If you have a hot, dry spot with excellent drainage, you must give thrift a try. A small, tidy plant, it covers itself with adorable bobbing pink flowers. It's a charming groundcover, edging plant, or rock garden feature. When planted in large groups, it forms a mat of attractive grassy foliage and colorful marble-size balls of flowers. Also called sea pink, this tough plant tolerates wind, sea spray, and is drought-tolerant. They do need well-drained soil to prevent root rot.
Take a walk down the primrose path and you'll never look back! Primroses are a classic cottage flower and are popular with collectors. They covet the hundreds of different primroses available, especially some of the tiny rare alpine types. Many are staples of cottage gardens and rock gardens, while others provide spring color to damp places, rain gardens, and bog gardens. Their basal rosettes of oval leaves are often puckered or are very smooth. The colorful flowers may be borne singly or rise in tiered clusters, or even spikes. Provide humus-high soil that retains moisture and some shade for best results.
Perhaps the best-loved perennials, herbaceous peonies belong in almost every garden. Their sumptuous flowers—single, semidouble, anemone centered or Japanese, and fully double—in glorious shades of pinks and reds as well as white and yellow announce that spring has truly arrived. The handsome fingered foliage is usually dark green and remains good-looking all season long. Provide deep rich soil with plenty of humus to avoid dryness, and don't plant the crowns more than 2 inches beneath the surface. But these are hardly fussy plants. Where well suited to the climate, they can thrive on zero care.
Lupine draws the eye skyward with its gorgeously colored and interestingly structured flower spikes. Bicolor Russell hybrids are the most popular type. Their large pea-like flowers come in amazing colors and combinations, clustered in long spikes on sturdy stems. Lupine prefers light, well-drained soil that is slightly acidic, and it does not tolerate heat or humidity well. It performs best in areas with cool summers, especially the Pacific Northwest.