Irises are one of those timeless floral beauties that can transform any landscape into a dazzling display of color. Whether you're new to gardening or an experienced green thumb, irises are a must-have addition to your garden. With their vibrant hues, striking forms, and easy-care nature, these flowers offer endless possibilities for design and enjoyment. They're usually deer and rabbit resistant, too! Let's take a look at the different types of iris and the growing conditions they're suited for, and show you how they can best be used to beautify your garden.
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The Beauty of Irises
Irises have been gracing gardens for centuries. Named after the Greek goddess Iris, who personified the rainbow and was the messenger between gods and mortals, these flowers reflect a spectrum of colors and a touch of mythological magic. Ancient civilizations, including the Egyptians, Greeks, and Romans, revered irises not just for their beauty but also for their medicinal properties. Fast forward to the 19th century when irises were popularized in Europe, with hybridization creating the stunning array of varieties we adore today.
The classic iris shape features three upright petals (standards) and three drooping petals (falls). Some, such as the bearded iris, have a very full, frilled, extravagant floral appearance with sturdy, substanial foliage - think Mae West, perhaps. For those of you who prefer the subtle elegance of Audrey Hepburn or Grace Kelly, there are the beardless Dutch and Siberian iris with grassier foliage and more slender petals that often resemble a graceful bird in flight. And for a truly impressive, over-the-top display, you can look to the dinnerplate-sized flowers of some Japanese iris, which put one in mind of Princess Di floating down the aisle in her extravagant wedding gown.
While the above ground parts of iris are similar, what's underneath can be quite different. Iris grow from either rhizomes (bearded, Louisiana, Japanese, Siberian) or bulbs (Dutch). Rhizomes of bearded and Louisiana iris should be planted in late summer or early fall; plant bulbous iris in the fall. Japanese and Siberian iris form more slender rhizomes with many fibrous roots and are more often found as containerized plants which can be planted whenever they are available. Bare roots of these types can be planted in spring or fall.
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Why Plant Irises?
- Stunning Visual Appeal
Irises are renowned for their spectacular blooms. With colors ranging from deep purples and blues to sunny yellows, soft pinks, vivid orange, red, and pristine whites, they can suit any garden palette. The intricate structure of their petals adds visual interest, whether you’re aiming for a formal garden or a wild, cottage-style look. Their tall, graceful stems create vertical interest in flower beds, making them a focal point wherever they're planted.
- Versatile Design Use
Irises are incredibly versatile in garden design. They can be used as:
Borders and edging: Tall bearded irises make a striking border, especially when paired with shorter perennials, and dwarf bearded types are perfect for edging.
Water garden features: Japanese, Louisiana, and pseudata irises thrive in wet conditions, making them perfect for water gardens, rain gardens, or along the edge of ponds.
Mixed bed and cottage garden elements: Their bold flowers blend beautifully with other perennials like peonies, daylilies, and delphiniums for a lush, vibrant look.
Spring color for woodland gardens: Native dwarf crested iris prefer partially shaded sites.
Rock garden plants: Reticulated iris and other dwarf species provide early spring color in rock gardens.
- Low Maintenance
Once established, most iris species are quite hardy and drought tolerant. They require minimal care beyond occasional division, which makes them perfect for gardeners who want beauty without the hassle. They are generally pest resistant, though keeping an eye out for iris borers and ensuring good airflow around plants can help prevent issues.
Types of Iris and Where to Plant Them
Bearded Iris (Iris x germanica), Zones 3-10
By far the most familiar to gardeners, these are the ones your grandmother likely had in her garden. With over 60,000 cultivars, the only problem you'll have is deciding between them! While we usually think of the tall bearded iris, there are actually 6 different categories that encompass sizes from 8 to over 40 inches, and bloom times from March to early June:
Miniature Dwarf: Up to 8 inches tall, the earliest blooming (March). Good candidates for rock gardens and massing in drifts. You may find these hybrids listed as I. pumila.
Standard Dwarf: 8-16 inches tall, blooming after the miniatures. Plant in clumps for best effect.
Intermediate: 6-27 inches tall with a bloom period that overlaps the standard and tall bearded types. They blend smaller size with the branching capabilities and color variations of tall beardeds.
Border: These share the size of the intermediate with the blooming period of the tall bearded.
Minature Tall: Also called "table irises" due to their suitability for floral arrangements. Smaller and daintier blooms on wiry stems grow 16-27" tall.
Tall: The most common type, growing over 27 inches. Multiple flowers per stem, often with branched stems adding to the floral display. Depending on cultivar, they bloom sometime in May or early June.
Where to plant: These are the ones for the hottest, sunniest part of your garden. They'll tolerate partial shade, but flower best in full sun. Well-drained soil is imperative, or the fleshy rhizomes may rot.
Growing Tips: Rhizomes should be planted 6 to 12 inches apart depending on the size of the variety, with 1/3 above the soil level, and do not mulch. They bloom from the top down, so you can snip off individual flowers as they fade, or simply cut back the stem at an angle where it meets the foliage once the entire stalk is finished. Remove any damaged or diseased leaves at the base of the rhizome (do not compost). Cut foliage back by half in an angled fan shape in late summer to tidy foliage if necessary. Remove all foliage at the base after first frost to avoid overwintering any pests or disease. In warm weather climates they will not go dormant, so clean foliage as needed. To keep them blooming well, dig and divide every 3 to 5 years in late summer, cutting back leaves to about 10 inches, and make sure each division has at least one fan of foliage.
Reblooming Varieties: There are a handful of "reblooming" cultivars that may or may not perform as advertised depending on your individual growing conditions, 'Frequent Flyer' is repeat bloomer particularly recommended for Southern California coastal gardens.
Siberian Iris (Iris sibirica), Zones 3-8
Siberian irises are known for their slender, graceful foliage and elegant flowers. They tend to have a more delicate appearance compared to other irises. Recent breeding has expanded the color range from blue, purple, and white to include yellow, pink, and red, and created flower forms that are frilly, multi-petaled or double. These are the easiest to grow in a typical garden bed, and are the most adaptable. On average, the foliage grows 2' high with a similar spread, with blooms rising up to another foot above the leaves. Blooming is generally in the May-June time frame and lasts about 2 weeks, as is typical of most iris.
Where to plant: Site in full sun to part shade and moist, fertile, well-drained soil. They are attractive in mixed perennial beds or borders, and can also be grown in somewhat boggy areas and rain gardens, and in containers.
Growing Tips: They prefer consistent moisture until after blooming and to keep foliage attractive, but can withstand periods of drought once established. Too much shade will reduce flowering and cause foliage to become floppy.
Japanese Iris (Iris ensata), Zones 4-9
Japanese irises are prized for their large, billowy, flattened flowers and intricate patterns. They bring a touch of elegance with their distinctive blooms, which begin after both bearded and Siberian Iris, in early to mid-summer. Again, the blooming period is a relatively short couple of weeks, but their exquisite beauty makes it worth the garden space. Flowers may be single or double and 3-6 inches wide, but "Dinnerplate" varieties can reach 8 inches wide. Colors include shades of blue, purple, lavender, white, and pink are are often veined, rimmed, or streaked with contrasting colors. Plants are roughly 2-3 feet tall and up to 3-4 feet when in flower.
Where to Plant: In nature, they are found in full to part sun in boggy sites that are drier in winter. During the growing season they can be grown in as much as 6 inches of standing water. Despite this, they MUST have well-drained soil in the winter to prevent root rot. They are a natural choice for planting at water's edge. As a bog or pond plant they should be kept in pots that can be removed during fall and winter to a drier spot. If you're able to provide supplemental water, they can be grown fairly easily in typical garden beds or containers.
Growing Tips: Do not add lime or bone meal as they prefer a slightly acid soil and high PH may damage the plants. Heavy feeders, so use a fertilizer for acid-loving plants in the spring, but do not fertilize new transplants. Some afternoon shade can be beneficial in areas with hot summers.
Iris pseudata, Zones 4-9
Where to plant: Give them full sun for best flowering and plant in average to wet soil. Plant toward the back of borders or as a tall, vertical accent in beds. They're a great option for wet, heavy clay soil, or as a marginal pond plant. I had 'Yarai' planted in a container where it did quite well, and have since moved it to a bed with a couple of new Siberian Iris cultivars, and have had no issues. It is a truly adaptable plant, quite striking in bloom.
Growing Tips: Heavy feeders, so be sure to fertilize with a balanced formula in spring and after blooming, but do not apply in fall. Mulch to prevent frost heaving over winter and to conserve soil moisture.
Louisiana Iris
Where to plant: Site them in full sun for best flowering. Watering is most important when growth begins in fall and in spring until blooming commences. Plant them in damp spots or among other perennials that favor moist conditions year round, such as ligularia, milkweed (asclepias incarnata), lobelia, turtlehead (chelone), hardy hibiscus (hibiscus moscheutos), and obedient plant (physostegia). Give them plenty of space as rhizomes can spread widely where they're happy. Perfect as a potted pond plant with the roots set just a few inches below the water level. Hardy zones 4 to 9, but bring in potted pond plants where water freezes for much of the winter so that growth can continue.
Growing Tips: Keep rhizomes mulched to avoid sunburn.
Other Useful Iris Species and Hybrids
Reticulated Iris (I. reticulata), Zones 5-9: Another bulbous iris, these are a dwarf species growing about 5-6 inches high. These bloom in later winter. Perhaps it's because we're not accustomed to seeing iris bloom at that time of year, but despite their hardy nature they always seem so delicate and fragile. These will perennialize well in full to part sun and well-drained soil. Plant them near walkways or along wooded paths, on sunny slopes, under deciduous shrubs, or below a blanket of low-growing groundcover plants like creeping phlox. They make a charming display when grown in shallow containers, and can also be forced indoors. There are several named varieties, with deep blue 'Harmony' being the most easily sourced. 'Katherine Hodgkin,' with its palest of blue petals marked with soft yellow and tiny blue spots, is an ethereal delight. Iris danfordiae may be combined with I. reticulata in some pre-mixed bulb packages to add a bright shot of yellow, but note that the blooming period Danford iris is extremely short. Reticulatas bloom for about 2 weeks, as is usual for most iris.
Dwarf Crested Iris (I. cristata), Zones 5-7: These low-growing (3-6") iris are native to the east and southeastern US. Their light blue flowers bloom in early spring. A rhizomatous species, they can spread quickly to form a groundcover in part to almost full shade. With enough water they can be grown in full sun, however. Valuable as a woodland groundcover or to stabilize partially shaded slopes.
Roof or Wall Iris (I. tectorum), Zones 4-9: So called because of the historical practice of growing them on the thatched roofs of houses in Japan--you can just grow them on the ground! A beardless rhizomatous iris growing to about 15" high, with large 6" wide blue flowers blooming in mid-spring. Grow in full sun to partial shade in rich, moist, well-drained soil. Arched, glossy, ribbed leaves add attractive texture to plantings. Can spread rapidly, so useful for groundcover in sunny or woodland locations, or on hillsides or slopes.