Irises, the national flower of France, with around 300 species, have become the most cultivated flowers in the world. For centuries they’ve been treasured by gardeners for their magnificent colors and elegance. They are named after the Greek goddess of the rainbow, Iris, due to its wide variety of colors. This low-maintenance, easy-caring perennials have captured the imagination of artists like Vincent Van Gogh too.
Native to the North Temperate regions of the world, irises come in diverse range of colors, such as purple, lavender, white, yellow, orange, pink, blue, and even brown. Some grow in swamps, some in deserts, some in the cold far north, and many in temperate climates.
Whether an iris will be perennial or not, depends on its root system. Based on their root system they are of two basic types: perennials that grow from rhizome, and bulbous that grow from bulbs.
This type of irises grows from typical rhizomes, a type of root which grows sideways, just beneath the soil surface. At times, these creeping rhizomes are partially visible above the soil line. These irises have overlapping, sword-shaped leaves. Rhizome irises bear three types of flowers: bearded, crested, and beardless.
Following are some popular rhizome irises:
Commonly known as the bearded iris or the German bearded iris, it is a group of hybrid irises. With over 100 cultivars, all produce showy, fragrant flowers with six petals. Out of six, three are upright (standards), and the remaining three are drooping (falls). In the center of each fall, there is a furry line, known as a beard, resembling a caterpillar. Their leaves are flattened and sword-like. They perform best in neutral to slightly acidic, humus-rich, well-drained soil. These average maintenance plants are classified into six groups, depending on height and flower size: miniature dwarf, standard dwarf, intermediate, miniature tall, border bearded, and tall bearded irises.
Flower Type: Bearded
Flower Color: Purple, blue, red, peach, yellow, orange, black, white
Flowering Season: Mid to late spring
Height/Width: 2-4 feet/1-2 feet
Sunlight Requirement: Full sun
USDA Zone: 3-10
Cultivars: ‘Crimson King’, ‘Gypsy Queen’, ‘Kurdistan’, ‘Oriflamme’
This low-growing perennial carpets the ground with narrow, sword-shaped, pointed, dark green leaves. This dwarf Eastern U.S. native has a special appeal to woodland gardeners. Its 6-inch-high flowers are adorned with blue-lilac petals, each with a white patch and yellow or orange hairs on each of its outer petals or falls. Unlike the bearded iris, here, the hairs form a comb or raised ridge instead, which somewhat looks like a cockscomb. This low-maintenance plant enjoys moist, acid to alkaline, clay, or loam.
Flower Type: Crested
Flower Color: Blue-lilac
Flowering Season: Early to mid-spring
Height/Width: 6-9 inches/6 inches-1 foot
Sunlight Requirement: Full sun to partial shade
USDA Zone: 4-10
Cultivars: ‘Baby Blue’, ‘Dash It All’, ‘Celestial Gem’, ‘Eco White Angel’
Native to Japan, China, Korea, and Russia, this rhizomatous herbaceous perennial features a huge orchid-like showy flower. The flowers are broader and more flattened than the other types, rising on erect, sturdy stems atop a dense clump of sword-shaped linear green leaves with prominent midribs. This easy-to-grow iris loves humus-rich, medium to wet acidic soil.
Flower Type: Beardless
Flower Color: Blue, lavender, violet-red, pink, white
Flowering Season: Early to midsummer
Height/Width: 2-4 feet/1-2 feet
Sunlight Requirement: Full to partial sun
USDA Zone: 4-9
Cultivars: ‘Alpine Majesty’, ‘Flying Tiger’, ‘Rose Queen’, ‘Hue and Cry’
It is another rhizomatous herbaceous perennial variety native to Northern Asia. It is adored by gardeners due to its delicate flowers and long, dark green, sword-like leaves. The leaves remain attractive even after the blooming period is over, changing to a nice golden during fall and rusty red-brown with the first frost. This easy-to-grow, low-maintenance, drought-tolerant species performs well in rich and well-drained, neutral to slightly acidic soil.
Flower Type: Beardless
Flower Color: Blue, purple, red-violet, yellow
Flowering Season: Late spring to early summer
Height/Width: 2-4 feet/1-2 feet
Sunlight Requirement: Full to partial
USDA Zone: 3-8
Cultivars: ‘Ruffled Velvet’, ‘Butter and Sugar’, ‘Silver Edge’, ‘Cambridge’
Also known as the water flag, this perennial species, native to temperate regions of Europe, Asia, and northern Africa, is commonly grown for its showy yellow flowers. Its sword-like leaves are greenish-gray, flat, and erect with a raised midrib and have sharply pointed tips. Its large, yellow flower petals fold back on themselves and droop around the outer edges of the flower. This low-maintenance plant thrives well in medium to wet acidic soil.
This iris variant can be invasive, i.e., it can spread prolifically and may easily take over a small pond. To avoid this, try planting it in a basket to keep it contained around the margins.
Flower Type: Beardless
Flower Color: Yellow
Flowering Season: Summer
Height/Width: 3-5 feet/2-2.5 feet
Sunlight Requirement: Full sun to partial shade
USDA Zone: 5-9
Cultivars: ‘Roy Davidson’, ‘Variegata’, Golden Fleece, Alba
Louisiana irises are comprised of five iris species Iris brevicaulis, Iris fulva, Iris giganticaerulea, Iris hexagona, and Iris nelsonii. These irises are native to the coastal swamps of the U.S. state of Louisiana, particularly around New Orleans. Like other rhizomatous types, their leaves are also narrow, green, and sword-like. They prefer rich, acidic soil with plenty of moisture.
Flower Type: Beardless
Flower Color: White, purple, red, yellow, pink, gold, brown, lavender, burgundy, blue
Flowering Season: Late spring to midsummer
Height/Width: 2-3 feet/1-2 feet
Sunlight Requirement: Full to partial sun
USDA Zone: 4-10
Cultivars: ‘Red Velvet Elvis’, ‘Cajun Sunrise’, ‘Professor’ series’ (‘Professor Barbara’, ‘Professor Ike’ , ‘Professor Neil’ )
As the name implies, this type of irises grows from round or pear-shaped bulbs. Unlike the rhizome varieties, here the bulbs remain 2-5 inches below the ground. Also, they are noticeably smaller than rhizome irises, both in height and flower size. They require a period of dormancy after they finish blooming, and replenish in the next season. These bulbous irises grow in dry areas. There are two types that can be easily distinguished from one another by their bloom time.
It is a hybrid iris developed by crossing two varieties of Iris xiphium (var. praecox from Spain and var. lusitanica from Portugal) with Iris tingitana from North Africa. The blooms of these bulbous irises amaze gardeners with their striking color palettes. Their fan-shaped flowers, with three upright petals and three drooping petals, add elegance and beauty to any garden. These easy-growing plants can tolerate a range of soil types, including acidic, clay, sandy, and loamy, as long as it is well-drained.
Flower Color: Pale blue, lemon, deep purple, bronze, gold
Flowering Season: Late spring to early summer
Height/Width: 1.5 – 2 feet/6-12 inches
Sunlight Requirement: Full sun to partial shade
USDA Zone: 5-9
Cultivars: ‘Yellow Queen’, ‘Wedgwood’, ‘Imperator’, ‘White Excelsior’
Also known as dwarf iris, these early spring bloomers are native to Turkey, the Caucasus, Northern Iraq, and Iran. These low-growing irises splash the landscape with their fragrant, delightful blue and purple blossoms with golden crests and white streaks on the falls, appearing on the naked stems. They bear narrow, linear, 4-sided, grass-like leaves that eventually disappear by late spring as the plant goes dormant. They grow best in well-drained soil, tolerating acidic, clay, sandy, and loamy soils.
Flower Color: Purplish-blue, yellow, and white
Flowering Season: Late winter to early spring
Height/Width: 6 -12 inches/6 – 8 inches
Sunlight Requirement: Full sun to partial shade
USDA Zone: 4-9
Cultivars: ‘Pixie’, ‘Harmony’, ‘George’, ‘Katharine Hodgkin’
When we try to imagine an iris, the first thing that comes to our mind is the plethora of bold hues, most of which are imported. The ones that are discussed above, for instance, Japanese, Siberian, and Dutch irises, do not have their roots in U.S., belonging to Europe and Asia. However, there are 28 majestic beauties, including copper iris, dwarf lake iris, and Douglas iris that are native to U.S.
Best Blue Irises: ‘Blue Desire’, ‘Queen’s Circle’, ‘Cloud Ballet’
Best Pink Irises: ‘June Krauss’, ‘Pink Attraction’, ‘Magical’
Best Red Irises: ‘Lady Friend’, ‘Vizier’, ‘Chief Quinaby’
Best Yellow Irises: ‘Smart Money’, ‘That’s All Folks’, ‘Highlighter’
Best White Irises: ‘Skating Party’, ‘Sly Fox’, ‘Laced Cotton’
Best Purple Irises: ‘About Town’, ‘Attitude’, ‘ Aello’
Best Black Irises: ‘Here Comes the Night’, ‘Swazi Princess’, ‘Coal Seams’
Tallest Irises: ‘Absolute Treasure’, ‘Arctic Express’, ‘Decadence’
Dwarf Irises: Iris cristata, dwarf lake iris, coastal plain dwarf violet iris, clackamas iris
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