Iris is a genus of 310 species and is in the plant family Iridaceae that also included gladiolus, crocus and freesia. The plants are all perennial and grow from rhizomes or bulbs. The iris with rhizomes have 2-10 sword shaped leaves that grow in dense clumps while the iris with bulbs have 2-10 narrow leaves. The flowers appear on a long erect stems that may be branched. The flowers consist of three outer sepals called falls that usually are spreading or droop downward, and three inner petals called standards, that are upright. The standards may be delicate or large and showy and the falls may have various attractive and distinctive markings including a patch of yellow or white, known as a signal, or a row of hairs known as a beard. Petals and sepals may be lavender, blue, purple, white, pink, red, yellow, brown and combinations of these that resemble a rainbow.
Iris can grow in a variety of soil types from dry to wet and some grow in shallow water. Bulbus iris prefer drier soil than rhizomatous iris and both grow well in full sun to partial shade. The bloom time various greatly and with careful planning it is possible to have some species of iris blooming from mid spring to mid summer.
The genus name, Iris, honors the Greek goddess Iris whose name, ἶρις (îris) means rainbow and may refer to the wide variety of flower colors.
Photo Credit Dcrjsr, Wikimedia Commons
The environmental conditions of the Southwest have favored at least six species of native iris there but they may be native to other regions also. The iris described here are native to at least one state in the Southwest.
Zigzag Iris ( Iris brevicaulis)
Native to east Texas and Oklahoma as well as areas in the Southeast and Midwest, zigzag iris grows in swamps, shaded damp wooded, and bottomlands. Also known as short-stemmed iris, Lamance iris, or leafy blue flag, it is a good choice for using along waterways and for rock and woodland gardens.
Height: 10-12″
Bloom Time: Mid spring
Bloom Color: Blue-purple to pale blue-violet, lavender, white, with yellow signals
Light: Full sun to part shade
Soil: Average, medium moist to wet, well-drained, slightly acidic
USDA Hardiness Zones: 4-8
Photo Credit: Eric Hunt, Wikimedia Commons
Crested iris (Iris cristata)
Also known as lady’s calamus, crested iris is native to Oklahoma as well as places in the Midwest, Southeast, Mid Atlantic, and New England. It grows on rocky hillsides, in ravines, on mountain ledges, and along streams. Flowers are fragrant. Crested iris can be used as a groundcover and is useful in shade, rock and fragrance gardens.
Height: 4-9″
Bloom Time: April-May
Bloom Color: Blue, pale blue, lavender, purple, lilac, and rarely white or pink
Light: Part shade but tolerates full sun
Soil: Average to fertile, high to medium moist, well-drained
USDA Hardiness Zones: 3-9
Photo Credit: Eric Hunt, Wikimedia Commons
Copper Iris (Iris fulva)
Known for its unusual color and drooping standards, copper iris is native to Texas as well as places in the Southeast, and Midwest. It is found in flooded areas and wet places such as marshes, stream banks, swamps, and wet pastures, normally in water up to 6 inches deep. The flowers attract hummingbirds. Good choice for bird, pollinator, wildlife, water, bog, and rain gardens.
Height: 18-31″
Bloom Time: April to June
Bloom Color: Copper-colored to deep red, occasionally yellow
Light: Full sun
Soil: Fertile, organically rich, moist to wet, acidic
USDA Hardiness Zones: 3-10
Photo Credit: James Henderson, Wikimedia Commons
Giant Blue Iris (Iris giganticaerulea)
Giant blue iris is native to Texas as well as areas in the Southeast. Also known as giant blue flag, it grows in shallow freshwater, clearings within swamps, wet meadows and marshes, and it is tolerant of brackish water,
Height: 28-71″
Bloom Time: Early to mid spring
Bloom Color: Shades of blue, lavender and violet, rarely white.
Light: Full sun to partial shade
Soil: Fertile, organically rich, moist to wet, acidic
USDA Hardiness Zones: 7-11
Photo Credit: Irvin Louque, Wikimedia Commons
Rocky Mountain Iris (Iris missouriensis)
Also known as Missouri flag and western blue flag, Rocky Mountain iris is native to Arizona, New Mexico as well as places in the Midwest and Rocky Mountain area, and on the Pacific coast. It is found at high elevations in alpine meadows, pastures with ground water near the surface, open woodland, and on coastal hills at sea level. The key factor in its distribution appears to be having extremely wet conditions in spring before flowering, and very dry condition for the rest of the growing season.
Height: 8-16′
Bloom Time: May-July
Bloom Color: White, yellow, blue, purple
Light: Sun
Soil: Moist to wet (needs moisture especially at flowering time)
USDA Hardiness Zones: 3-8
Photo Credit: Walter Siegmund, Wikimedia Commons
Virginia Iris (Iris virginica )
Virginia iris is native to Texas and Oklahoma as well as place in the Midwest, Southeast and Mid-Atlantic where it grows in wet areas, such as marshes, wet meadows, swamps, and river bottoms. Also called southern blue flag, it is an excellent choice for a pond margin, water garden or rain garden.
Height: 2-3′
Bloom Time: May to July
Bloom Color: Light blue to deep violet, rarely white
Light: Full sun
Soil: Humusy to sandy, moist to very wet, acidic
USDA Hardiness Zones: 5-9
Photo Credit: Eric Hunt, Wikimedia Commons
For the purpose of this article, the Southwest includes the states of Texas, Oklahoma, New Mexico and Arizona. Other states often associated with the Southwest are included in other geographic areas. The key factor linking these four states is aridity. The area includes high dry plains and true deserts as well as spurs of the Rocky Mountains. Only Texas has a coast on the ocean which brings more precipitation and humidity to east Texas and Oklahoma than elsewhere in the area. In addition to the ocean, the Rio Grande and Colorado Rivers are significant water features in the area. Although temperatures in the mountains can be cool, most of the area experiences hot temperatures for a long period each year.