Beautiful Irises
Perennial’s numerous species bloom vividly and bountifully.
One of the oldest and best-known perennials in the home landscape is the bearded iris, sometimes called a German iris or a flag. But the genus Iris contains almost 300 species, and many irises have been hybridized extensively.
In the Greek language, the word “iris” means rainbow, which is fitting since the flowers come in a rainbow of colors. Irises have a rich history that dates to A.D. 500. They were brought to the New World by European
settlers. Records show them in Virginia gardens as Perennial early as the 1600s.
Most species of iris are perennial plants but can be divided into two distinct abounds with types — those grown from a bulb, or “bulbous” irises, which include the Dutch numerous
iris and the reticulated iris; and those that grow from a rhizome, or “rhizomatous” irises. A rhizome is a modified stem that grows horizontally, species sending out roots and shoots.
Of the rhizomatous types, there are three classifications — bearded, beardless and crested. Rhizomatous irises include the bearded or German iris, the Louisiana iris, Japanese iris, Siberian iris and the native woodland crested iris.
Iris plants are monocots, meaning their flower parts are in groups of three. In general, three sepals face downward and are referred to as “falls,” while the three upturned petals are called “standards.”
By far the most common iris grown in gardens is the bearded iris, Iris germanica. After a century of intense hybridization, they are often referred
to now as bearded hybrids.
The name refers to the bushy “beards” that appear on the falls of the flower and help pollinators find the pollen.
According to the American Iris Society, there are six different groups of bearded irises based on size: miniature dwarf, dwarf, intermediate, miniature tall, border and tall. Their bloom times range from late winter to early summer. Some newer varieties bloom again in late summer or early fall and are known as “rebloomers.”
In Arkansas, the most popular bearded type is the tall bearded iris. Its flowers grow along bloomstalks 28 inches tall or taller.
The rhizomes are planted shallowly, with part of the rhizome exposed above ground — and no mulch should cover the rhizome. A spacing of 12-24 inches is best. They like a welldrained, light soil with at least 6-8 hours of sunlight a day.
If you have heavy soils, amend with organic matter. Fertilize with a complete fertilizer in the spring and again a month after bloom. Avoid putting the fertilizer directly on the rhizome.
A common problem can be the competition of grass and weeds. Make sure you clean the garden well before planting. Once established, bearded irises are very drought tolerant and relatively carefree — but you will need to lift and divide them eventually.
The rhizomes multiply horizontally and can form a mat over time. If they get too crowded they will stop blooming. They should be divided every three to five years, or sooner if their blooms begin to decline.
The best time to divide them is from mid-July to mid-August since the plants are usually dormant then. Since you plant iris rhizomes shallowly, you want to allow time for them to re-establish before cold weather hits.
You can thin a clump, leaving parts of the rhizome mass still in the ground; but digging up the whole clump and separating them is more common because the older rhizomes rot away leaving holes where mother plants once stood.
Some varieties are prone to diseases, and so many growers soak their divisions in a 10 percent bleach solution for 10 to 15 minutes, rinsing and then drying them before replanting.
Choose strong rhizomes with healthy fans to replant. Fans are the cluster of leaves that come from the rhizome. When dividing, you want to cut the fan back so it’s only 6 to 8 inches tall. Cutting helps sanitation, but it also prevents the wind from uprooting the shallowly planted iris until its roots re-establish.
Bearded irises typically bloom for two to five weeks, depending on the vigor of the plant. When planting, choose early, midseason and late-blooming varieties to extend the flower display in your garden.
A common question is whether it’s necessary to cut back the foliage after bloom. Unless you are dividing them, there is no reason to cut the leaves of bearded irises. Many growers do cut the leaves because they have hundreds (or thousands) of iris plants and want to provide better air circulation and sunlight penetration to reduce leaf-spotting diseases.
If you just have a few iris plants in your garden, there is no need to cut the foliage back.
CRESTS
While tall bearded irises are by far the most popular varieties here, there are several other irises that are great garden performers and will thrive in different locations.
Our native crested irises are much smaller plants that love the shade. In the wild they are typically found in deciduous forests in light to fairly heavy shade.
A wild crested iris only grows 6 inches tall, and the rhizomes are near the surface but typically covered with soil or leaf mulch. These little plants have lovely clusters of light blue or violet flowers that last two or three weeks in the spring. There are some white-blooming forms as well.
After bloom, the grass-like foliage can serve as a groundcover. Crested irises do best in a well-drained but rich site. They do not have to be divided unless you want to propagate them, and early fall is the best time to do so.
NO BEARDS
Beardless rhizomatous irises include the Louisiana, Japanese and Siberian iris plants. They do like full sun but they are planted in the soil, not at the soil level, and they need much more water than their bearded cousins.
Siberian irises like even moisture while Japanese irises like as much water as you can provide — but neither like to have wet feet in the winter.
Louisiana irises will grow in standing water year-round but will also do well in the ground as long as they don’t dry out.
Louisiana irises are native to Louisiana and the Gulf Coast. The wild copper iris is found in Arkansas, too, and like other Louisianas, likes swamps and moist areas. While that is where they grow in the wild, Louisiana irises also tolerate soil moisture conditions in a home garden. But they are not drought tolerant — they do need some supplemental watering in hot, dry summers.
They need 6-8 hours of sunlight a day but would like a little protection from the hot afternoon sun if possible.
Plant them 1 inch deep in organic soils. They will tolerate heavy clay soils, as they retain moisture well, but the addition of organic matter is helpful. Depending on the variety, mature plant size could be a foot to 6 feet tall, with flowers in a wide range of colors.
The purest red color available in an iris is found among the Louisiana irises.
Cut back the flower stalk after bloom. Clumps spread rapidly in good conditions, so space them several feet apart to give them room to grow.
Japanese irises (Iris ensata) and Siberian irises (Iris siberica) are similar in appearance, but the flowers are typically larger on Japanese irises, and the plants are 3 to 4 feet tall. Japanese iris foliage also has a very distinct raised central rib, which the Siberians do not.
Siberian irises grow 2-4 feet tall and bloom several weeks after bearded irises.
Japanese irises are the last irises to bloom and have the largest and showiest blooms. Japanese irises are planted 3 to 4 inches deep in rich soil.
For both types, keep the soil moist after planting and water if there is not plenty of rainfall, particularly until blooming ends. Both are heavy feeders and should be fertilized with a complete fertilizer in the spring and just before blooming. These plants have large sword-like leaves and can be difficult to transplant once planted. Give them full sun.
These are all great choices for the perennial garden.
BULBS
The two bulbous irises are planted in the fall along with daffodils and tulips. The Dutch iris is not long-lived in our climate, but showy while it lasts. The reticulated iris is a tougher plant and blooms in early spring. They can colonize and come back each year.
Regardless of which iris you plant in your garden, or if you try them all, they can add much beauty to the landscape.
And if you want to learn more, consider joining an Arkansas iris society.
■ In Little Rock, the Central Arkansas Iris Society meets at 2 p.m. on the third Sunday of the month in Hillcrest Hall, 1501 Kavanaugh Blvd. The April meeting conflicts with Easter, so they have moved that meeting to president Phyllis Kirtley’s home, 265 Woodridge Lane in Benton at 2 p.m. Sunday, April 28.
Their annual iris show will be May 4, with free admission from 1-4 p.m. at Grace Lutheran Church, 5124 Hillcrest Ave., Little Rock. For more information about the show or touring Kirtley’s Display Garden, call her at (501) 626-7258.
■ The Hot Springs Iris Society meets at 2 p.m. on fourth Sundays except in April and December. They meet at Prince of Peace Lutheran Church, 109 Hobson Ave. in Hot Springs.
■ The White County Iris Society meets at 2 p.m. on the first Sunday of every month except January, June, July and August, at 605 E. Race St. in Searcy. For information, call Alice Jewell at (501) 268-6634. Their iris show will be April 26 at Regions Bank in downtown Searcy. The rhizome sale is scheduled for June 29 at the downtown Searcy farmers market.
■ The second annual Mountain View Iris Festival will be May 3 and 4 in the Courthouse Square in Mountain View. More information is at mountainviewirisfest.com.
The American Iris Society also has a website loaded with information about growing irises at irises.org.
Read Janet Carson’s blog at arkansasonline.com/planitjanet.