Iris

Bearded Iris -- Iris (hybrids)

Figure 1. Bearded iris.

Due to many decades of hybridization, this out-standing group of iris is no longer assigned to a specific species. It was often referred to as German iris in the past. The most common groups are dwarf, intermediate and tall.

Dwarf bearded iris (Iris pumila) grow from 3 to 11 inches in height. Intermediate bearded iris are 1 to 2 feet in height. Tall bearded iris reach 2 to 4 feet. They give a season of bloom extending from early May to mid June, one group merging into the other. The intermediates are actually results of crossing the early dwarfs and the late, tall bearded iris. They are, as the name implies, intermediate in season of flowering and in height. The tall bearded iris are the most popular type in home gardens and landscapes.

FLOWERS

Iris have orchid-like flowers. Nine to 12 buds are usually found growing on short side branches on each stem. Each blossom lasts about three days.

Three upright petals are called standards. Three sepals hand downward and are known as falls. Iris may have standards and falls of the same color or standards may be one color and falls a different color. Principal iris colors are lavendar, blue, white, purple, rose-red, yellow, pink, brown or various combinations and blends of these colors. The beard is the fuzzy, fringed appendage above the falls.

CULTURE

The two major requirements for suc-cessfully growing all classes of bearded iris are full sun and good drainage. The plants grow well in almost any good garden soil, but are less susceptible to disease, such as root rot, in soils of only moderate fertility. Extremely heavy, rich soils tend to produce soft growth. This increases problems with root rot, the most serious problem with iris.

Iris should not be crowded by other plants that over-shadow or mat closely about root and foliage. Keep iris free of weeds by practicing clean, shallow cultivation. Free air movement in and about iris plants is the best insurance against foliage diseases.

WHERE TO PLANT

Bearded iris are excellent for planting in borders, beds and foundation plantings. Where heavy, poorly drained soils are a problem, beds can be raised slightly above paths or sod areas to provide the necessary drainage.

Prepare beds a week before planting to allow the soil time enough to settle. Deep spading assures an ideal planting bed for iris.

The use of barnyard manure on iris should be discouraged, since it favors development of root rots. Well rotted manure can be used when it is carefully worked into the soil, but surface applications are not advisable.

WHEN AND HOW TO PLANT

Bearded iris can be divided or planted almost any time, but late July or August is the ideal time to plant iris in North Dakota.

DIVISION OF OLD CLUMPS

Bearded iris and many of the beardless types grow from an underground structure called a rhizome. This is a fleshy stem from which extend the true, stringy roots. These rhizomes branch and in time overgrow and crowd each other so that it is necessary to dig and divide every three to four years under ordinary culture.

Figure 2. Ready for planting.

The division should be reduced to a single, current-season rhizome with a single fan of leaves. Cut the leaves back to a length of 6 to 9 inches. Always discard weak or diseased parts.

Set the division in a shallow hole large enough to accomodate the division and the attached fibrous roots. Cover the top of the rhizone with only 1/2 inch of soil. Depth of planting is particularly important in heavy, clay soils where drainage may be impeded.

Plant four to six single divisions 12 to 15 inches apart to form a group. Iris groups should spaced about 4 feet apart. If set closer, plants will become crowded quicker and have to be reset more often. Planting seed is not practical for the amateur. Iris do not come true from seed!

HARDINESS

Iris are generally hardy in North Dakota. They will not however, stand being under water for any length of time. Iris may be covered by mulch during winter. Clean flax straw is good. Mulch is especially necessary if iris are planted in an exposed location and not protected by a blanket of snow.

CULTIVARS

As with many other ornamentals, there are many hundreds of cultivars of bearded iris. Since hardiness is important in North Dakota, the list on the back page contains some of the proven and reliable cultivars.

The large flowers produced by the bearded iris discussed above are second to none for showiness in garden landscapes. However, the foliage may be deficient in quality throughout the growing season. The following iris species display longer or more graceful foliage and produce attractive fountain-like accents in the landscape. Quality flowers are an additional asset.

Siberian Iris -- Iris sibirica

Siberian iris are characterized by refined, grass-like foliage that provide an attractive accent all summer. Slender flower stalks give rise to elegant, beardless flowers, with the standards normally much shorter in length than the larger falls. Plants grow 1� to 3 feet tall in dense compact clumps. The rhizones are small tough and fibrous, and plants root quite deeply.

Siberian iris are of easy culture, thriving in most soils in full sun or light shade. They grow best, however, in fertile, moist soils. The range of colors, heights and bloom tissue is expanding steadily thanks to the efforts of hybridizers. Beds should be well prepared with organic matter as this iris will be a long-lived planting. Clumps eventually become matted and are best divided after 5 to 10 years. Divide in July or August and keep new transplants of this species fairly moist during root establishment. Some Siberian iris cultivars to consider are as follows:

• Butter and Sugar -- white, yellow falls
• Caesar's Brother -- pansy-violet
• Dewfull -- blue
• Ego -- deep wine -- blue, ruffled
• Fairy Dawn -- pale lavendar pink
• Flight of Butterflies -- blue, faint flue-white between veins
• Little White -- white, dwarf in height
• Orville Fay -- bright blue, navy-blue veins
• Persimmon -- large, mid-blue flowers
• Ruffled Velvet -- plum purple
• Sea Shadows -- mixed shades of blue and turquoise
• Sky Wings -- light blue and yellow ivory bicolor
• Snow Queen -- white
• Sparkling Rose -- rose-wine
• Steve Varner -- sky blue
• Super Ego -- lavender blue, weined purple
• White Swirl -- white, ruffled, wide falls

Spuria Iris -- Iris spuria

This species is sometimes called butterfly iris. It has characteristics similar to Siberian iris, but it is taller (2 to 3 feet), has broader leaves and larger, beardless flowers. Most common colors are blue-purple to lilac, but additional colors are readily available, including white and yellow. Spurias are becoming more popular, since they extend the iris bloom season and the ornate flowers are excellent for arrangements. They are effective when planted toward the back of flower borders.

Like Siberian iris, spurias prefer a rich soil and plenty of moisture. The short rhizomes can be divided in early spring or fall. Some excellent cultivars are as follows:

• Golden Lady -- yellow
• Highline Lavender -- lavender, flushed with yellow
• Imperial Night -- deep purple and bright yellow
• Morning Tide -- white with light blue veins
• Mrs. Tate -- light blue
• Premier -- lavender-blue with yellow flush
• Ruffled Canary -- white and yellow, ruffled
• Shelford Giant -- white and yellow, very large
• Sunny Day -- golden yellow, excellent

Yellow Flag -- Iris pseudacorus

This beautiful bearded iris is of special interest for growing wherever fertile, moist soils are available. It performs well in flower beds, growing 3 to 4� feet tall. It is effective along ponds or streams or any water feature in the landscape. The exquisite flowers are a brilliant yellow with darker veining, borne on stalks tightly held by the leaves. The bright green leaves result in a striking landscape accent even when plants are not in bloom. Plants can be divided in early spring. A double-flowered form is available under the cultivar name "Flore-Plena."

Cultivar Recommendations*

Brown-Bronze

• Autumn Leaves
• Malaysia
• Penny A Pinch

Cream/Yellow

• Cream Taffeta
• Kiss of Lemon

Deep Blue

• Blue Lustre
• Praise the Loan
• Navy Waves

Deep Violet

• Swazi Princess
• Study in Black
• Dusky Challenge

Gold

• Carolina Gold
• Golden Opportunity

Lavender-Violet

• Amethyst Flame
• Mary Frances
• Starcrest

Medium Blue

• Jean Hoffmeirter
• Sea of Joy
• Pistol

Bicolors (two colors falls darker than standards)

• Burning Desire (bronze-red/hazelnut brown)
• Camelot Rose (orchid/burgandy)

Wine & Roses

• (pink/violet)

Orange

• Fresno Calypso
• Orange Empire
• Tangerine Queen

Pale Blue

• Chico Maid
• Sea Captain
• Song of Norway
• Evening Echo

Peach

• Peach Sundae

Pink

• Cherished
• Chrub Choir
• Christa
• Tahiti Sunrise
• Vanity

Purple

• Purple Pomp
• Pandora's Purple

Red

• Firestone
• Post Time
• Samurai Warrior
• Chief Waukesha

Variegata (yellow standards and dark falls)

• Syncopation (yellow/red violet)
• Peking Summer (yellow/red)
• Blazing Saddles (yellow/red)
• Desert Echo (yellow/brown)

Rose -- Deep Rose

• Gracie Pfost, Raspberry
• Ripples
• Prom Night

Violet

• Yvonne B. Burke
• Wonderstruck

White

• Angel Choir
• Ice Sculpture
• Mt. Olympus

Yellow

• Lemon Brocade
• Lemon Mist
• Jeanie Price

Amoena (white or near white standards and colored falls)

• Navajo Blanket (white/violet)
• Tulip Festival (white/yellow)
• Gold and Ermine (white/gold)
• Lemon Crown (white/yellow)
• Mission Ridge (white/blue)
• Tulip Festival (white/yellow)

Bitone (two shades of same color)

• Twist of Fate (violet)
• Best Bet (blue)
• Gypsy Woman (yellow)

Plicata (stitched or stipled color on light background)

• Chinquapin (brown/yellow)
• Dot and Dash (dark violet/white)
• Wild Berry (red/white)
• Jesse's Song (violet/white)
• Radiant Apogee (yellow/white)
• Sentry (violet/white)
• Spinning Wheel (blue violet/white)
• Stepping Out (dark violet/white)
• Theatre (violet/white)
• Jeweled Starlight (yellow/white)

*Athur Jensen, 5508 S. University, Fargo, ND 58104, is an iris grower and has made helpful suggestions in compiling this list of recommended cultivars.

H-113, March 1993

Reviewed and reprinted, February 2008