FAMILY: Iridaceae

  • Perennials
  • Bulbs
  • Rhizomes
  • Varies by Species
  • Varies by Species
  • Poisonous/Toxic

Plant Details

A large and remarkably diverse group of 200 to 300 species, varying in flower color and form, cultural needs, and blooming periods (although the majority flower in spring or early summer). Leaves are swordlike or grasslike. Flowers (fragrant, in many kinds) are showy and complex in struc ture. The three inner segments (the standards) are petals; they are usually erect or arching but, in some kinds, may flare to horizon- tal. The three outer segments (the falls) are petal-like sepals; they are held at various angles, from nearly horizontal to drooping.

Irises grow from bulbs or rhi- zomes. In floral detail, there are three categories: bearded (each fall bears an adornment resembling a small, fuzzy caterpillar), beardless (each fall is smooth), and crested (each fall bears a comblike ridge instead of a full beard).

Described here are the irises most available in the South. Tall bearded irises (and other bearded classes) are the most widely sold; many new hybrids are cataloged every year. Specialty growers abound. A smaller number offer various beardless classes and some species. Retail nurseries carry bulbous irises for fall planting. Deer don't usually bother irises.

BULBOUS IRISES. Irises that grow from bulbs have beardless flowers. Bulbs go dormant in summer and can be lifted and stored until planting time in fall.

Dutch and Spanish irises. Zones US, MS, LS; USDA 6-8. The species that parented this group come from Spain, Portugal, Sicily, and northern Africa. (Dutch irises acquired their name because the hybrid group was developed by Dutch bulb growers.) Flowers are borne atop slender stems that rise from rushlike foliage. Standards are narrow and upright; oval to circular falls project downward. Colors include white, mauve, blue, purple, brown, orange, yellow, as well as bicolor combinationsusually with a yellow blotch on falls. Dutch iris flowers reach 34 in. across, on stems 1122 ft. tall; these are the irises sold by florists. Bloom is early spring in warm-winter regions, late spring in colder ones. Spanish irises are similar but have smaller flowers that bloom about two weeks later.

Plant bulbs in autumn, setting them 4 in. deep, 34 in. apart; give full sun. Bulbs are hardy to about 10F; in Upper South, apply a mulch in winter. Give regular water during growth and bloom. Bulbs can be left in the ground for several years where summers are dry; elsewhere, they should be lifted. After bloom, let foliage ripen before digging; store bulbs in a cool, dry place for no more than two months before replanting. Dutch and Spanish irises are good in containers; plant five bulbs in a 5- to 6-in. pot.

Reticulata irises. Zones US, MS, LS; USDA 6-8. The netted outer covering on the bulbs gives the group its name. These are classic rock garden and container plants, with flowers like small Dutch irises appearing on 6- to 8-in. stems in early spring. Narrow, blue-green leaves appear after bloom. Available species include I. reticulata, with 2- to 3-in. violet-scented flowers (purple, in the usual forms), and I. danfordiae, with bright yellow blooms. Pale blueflowered species I. histrio and large-flowered, blue-and-yellow I. histrioides may be carried by some specialists. Far more common are named hybrids such as 'Cantab' (pale blue with orange markings), 'Harmony' (sky-blue marked yellow), 'J. S. Dijt' (reddish purple), 'Katherine Hodgkin' (light greenish blue marked with white, yellow, and violet), 'Natascha' (palest blue flowers marked yellow), and 'Pixie' (deep blue marked gold and white).

Bulbs are hardy to about 10F and need some subfreezing winter temperatures to thrive. Plant in autumn, in well-drained soil in a sunny location; set bulbs 34 in. deep and 34 in. apart. Need regular moisture from fall through spring. Soil should be kept dry during summer dormant period; in rainy climates, lift bulbs in summer or grow in pots so you can control moisture. Divide only when vigor and flower quality deteriorate. Watch for slugs and snails.

RHIZOMATOUS IRISES. Irises that grow from rhizomes (thickened, modified stems) may have bearded, beardless, or crested flowers; among this group are the most widely grown types. Leaves are swordlike, overlapping each other to form flat fans of foliage.

Clumps become overcrowded after 3 or 4 years, and quantity and quality of bloom decrease. Lift and divide crowded clumps at best planting time for your area. Save large rhizomes with healthy leaves; discard old and leafless ones from clump's center. Break rhizomes apart or use a sharp knife to separate. Trim leaves, roots to about 6 in.; let cut ends heal for several hours to a day before replanting. If replanting in the same soil, amend it with organic matter.

Bearded irises. Zones US, MS, LS, CS; USDA 6-9. The most widely grown irises fall into the bearded group. More than a century of breeding has produced a vast array of beautiful hybrids. All have upright standards and flaring to pendent falls that have characteristic epaulette-like beards. Tall bearded irises are the most familiar of these, but they represent just one subdivision of the entire group. Eating any part of these causes gastric upset, and plants have poisoned livestock. In addition, some people get contact dermatitis from handling the rhizomes.

Dwarf and median bearded irises. These irises generally have flowers shaped like those of the familiar tall beardeds, but flower size, plant size, and stature are smaller. Median iris is a collective term for the categories standard dwarf, intermediate and border bearded, and miniature tall bearded.

Miniature dwarf bearded irises. Grow to 8 in. tall; flowers large for size of plant. Earliest to bloom of bearded irises (about six weeks before main show of tall beardeds). Hardy, need winter chill. Plants multiply quickly. Shallow root systems need regular moisture and periodic feeding.

Standard dwarf bearded irises. Grow 815 in. tall. Flowers and plants are larger than miniature dwarfs. Profuse bloom. Perform best with some winter chill.

Intermediate bearded irises. Grow 1528 in. tall, bear flowers 35 in. across. Flower later than dwarfs but one to three weeks before tall bearded irises. Most are hybrids between standard dwarfs and tall bearded selections and resemble larger standard dwarfs rather than border beardeds. Some give second bloom in fall.

Border bearded irises. Grow 1528 in. tallproportionately smaller versions of tall beardeds in the same wide range of colors and patterns. Bloom period is same as for tall bearded.

Miniature tall bearded irises. Grow 1528 in. high and flower at the same time as tall beardeds. Their small flowers (23 in. wide), narrower foliage, and pencil-thin stems give them appearance of tall bearded irises reduced in every proportion. Good for cutting and arrangementshence their original name, table irises.

Tall bearded irises. Among choicest perennials for borders, massing, and cutting. Easy to grow. Midspring flowers come on branching stems 2124 ft. high. All colors but pure red and green; patterns of two colors or more and blends produce infinite variety. Countless named selections are available. Modern hybrids often have elaborately ruffled, fringed flowers. Available variegated-foliage selections include 'Pallida Variegata' (often cataloged as 'Zebra'), with green leaves striped with cream; and 'Argentea', producing green leaves with white stripes. Both bear smallish blue-lavender flowers on stems to 2 ft. high.

Remontant (reblooming) tall bearded irises flower in spring, again in mid- to late summer or fall, depending on selection and climate. Plants need fertilizer, regular moisture for best performance. Specialists' catalogs offer increasing numbers of remontant tall beardeds.

BEARDLESS IRISES. Flowers in this group all have smooth, beardless falls but otherwise differ considerably in appearance from one type or species to another. Rhizomes have fibrous roots (unlike fleshy roots of bearded types); most prefer or demand more moisture than bearded irises. Many can perform well in crowded clumps but will eventually need division when performance declines. Timing varies; dig and replant quickly, keeping roots moist until planted. The following four hybrid groups contain the most widely sold beardless irises.

Japanese irises. Zones US, MS, LS, CS; USDA 6-9. Derived solely from I. ensata (formerly I. kaempferi), these irises feature sumptuous blossoms 412 in. across on slender stems to 4 ft. high. Flower shape is essentially flat. Single types have three broad falls and much-reduced standards, giving triangular flower outline; double blossoms have standards marked like the falls and about the same size and shape, resulting in circular flower outline. Colors are purple, violet, pink, rose, red, whiteoften veined or edged in contrasting shade. Plants have graceful, narrow, upright leaves with distinct raised midribs. Use in moist borders, at edge of pools or streams, or even in boxes or pots plunged halfway to rim in pond or pool during growing season.

Plants need much moisture during growing, flowering period. Both soil and water should be neutral to acid. If soil or water is alkaline, apply aluminum sulfate or iron sulfate (1 ounce to 2 gallons water) several times during growing season. Plant rhizomes in fall or spring, 2 in. deep and 112 ft. apart; or plant up to three per 12-in. container. Full sun. Divide about every 3 years, in early fall.

Louisiana irises. Zones US, MS, LS, CS; USDA 6-9. Approximately four species from the lower Mississippi region and Gulf Coast compose this group of so-called swamp irises. Graceful, flattish blossoms on stems 25 ft. tall, carried above and among leaves that are long, narrow, and unribbed. The range of flower colors and patterns is extensivenearly the equal of tall beardeds.

Specialists offer a vast array of named hybrids; some may carry the basic species as well. Zigzag iris (I. brevicaulis, sometimes listed as I. foliosa) has blue flowers with flaring segments carried on zigzag stems among the foliage. Copper iris (I. fulva) has coppery to rusty red (rarely yellow) blossoms with narrow, drooping segments. I. giganticaerulea is indeed a giant blue (sometimes white) with upright standards and flaring falls; stems to 4 ft. or more, with proportionally large leaves. I. hexagona also comes in blue shades with upright standards and flaring falls. I. xnelsonii, a natural hybrid population derived from I. fulva and I. giganticaerulea, resembles the I. fulva parent in flower shape and color (but also includes purple and brown tones) and approaches the I. giganticaerulea parent in size.

Plants thrive in well-watered, rich garden soil as well as at pond margins; soil and water should be neutral to acid. Locate in light afternoon shade. Plant in late summer; set rhizomes 1 in. deep, 1122 ft. apart. Mulch for winter where ground freezes. Divide every 3 to 4 years, in late summer or early fall.

Siberian irises. Zones US, MS, LS; USDA 6-8. The most widely sold members of this group are named hybrids derived from I. sibirica and I. sanguinea (formerly I. orientalis)species native to Europe, Asia. Clumps of narrow, almost grasslike leaves (deciduous in winter) bear slender stems to 4 ft. high (depending on selection), each bearing two to five blossoms with upright standards and flaring to drooping falls. Colors include white and shades of blue, lavender, purple, wine, pink, and light yellow.

Give plants partial or dappled shade, neutral to acid soil. Plant in spring or fall; set rhizomes 12 in. deep, 12 ft. apart. Water liberally from onset of growth until several weeks after bloom. Divide infrequentlywhen clumps show hollow centersin late spring or fall.

Spuria irises. Zones US, MS, LS, CS; USDA 6-9. In flower form, spurias resemble Dutch irises. Older members of this group had primarily yellow or white-and-yellow blossoms; I. orientalis (I. ochroleuca) has naturalized in many parts of the South, its 3- to 5-ft. stems bearing white flowers with yellow blotches on the falls. Dwarf I. graminea bears narrow-petaled, fragrant blue-and-maroon blossoms on foot-high stems. Modern hybrids show a great color range: blue, lavender, gray, orchid, tan, bronze, brown, purple, earthy red, and near blackoften with a prominent yellow spot on the falls. Flowers are held closely against 3- to 6-ft. stems, rising above handsome clumps of narrow, dark green leaves. Flowering starts during latter part of tall bearded bloom and continues for several weeks beyond.

Plant rhizomes in late summer or early fall, in rich, neutral to slightly alkaline soil; set them 1 in. deep, 1122 ft. apart. Plants grow well in full sun but will also take light shade for part of the day. They need ample moisture from onset of growth through bloom period but little moisture during summer. Divide clumps (not an easy task) infrequently; do the job in late summer or early fall.

I. albicans. YEMEN IRIS, WHITE FLAG. Zones US, MS, LS; USDA 6-8. Sterile hybrid originating in the Middle East, where it was often planted in Muslim graveyards. Popular passalong plant in the South, usually seen in older gardens and cemeteries. Sword-shaped leaves to 112 ft.; white flowers with yellow-and-white beards in very early spring. Easy to grow, needing only good drainage and a spot in full sun or light shade. Moderate to regular water; established plants take drought and neglect.

I. domestica (Belamcanda chinensis). BLACKBERRY LILY. Zones US, MS, LS, CS; USDA 6-9. Native to East Asia. Forms clumps of sword-shaped leaves in fanlike sheaves from slowly creeping rhizomes. Flowers are yellowish orange dotted with red; they appear on 3- to 4-ft.-high zigzag stems in summer. Each blossom lasts only a day, but new ones keep opening for weeks. As blooms fade, rounded seed capsules develop; they split open to expose shiny black seeds that look like blackberries (hence the plant's common name). Cut seed-bearing stems for unique dried arrangements. Effective in clumps in border. 'Freckle Face' grows to 1215 in. high; has slightly larger flowers with distinct red spots. 'Hello Yellow' is a dwarf form (2 ft. high) with unspotted yellow flowers. Plant rhizomes in porous soil, 1 in. deep and 1 ft. apart. Full sun or partial shade. Give regular water during growth and bloom.

I. foetidissima. GLADWIN IRIS. Zones US, MS, LS, CS; USDA 6-9. Native to Europe. Glossy evergreen leaves to 2 ft. make handsome foliage clumps. Stems 1122 ft. tall bear subtly attractive flowers in blue-gray and dull tan; specialists may offer color variants in soft yellow and lavender-blue, as well as a form with white-variegated leaves. Real attraction is large seed capsules that open in fall to show numerous round, orange-scarlet seeds; the cut stems with seed capsules are attractive in arrangements. Grow in partial to full shade. Likes moist soil, but established plants tolerate drought. Mulch in fall in Upper South. Ingestion causes gastric upset.

I. laevigata. RABBIT-EAR IRIS. Zones US, MS, LS, CS; USDA 6-9. Native to China, Korea, Japan. Smooth, glossy leaves reach 112212 ft. long, to 1 in. wide. Flower stems grow to about the same height, bearing violet-blue blossoms with upright standards and drooping falls enlivened with yellow central stripes. Bloom period comes after that of tall bearded irises. Named color variants include kinds with white, magenta, and patterned purple-and-white blooms. 'Variegata' sports crested flowers in light blue and leaves with longitudinal white stripes. There are also selections whose standards mimic falls in shape, pattern, and carriage, producing the effect of a double blossom. This is a true bog plant, growing best in constantly moist, acid soileven in shallow water. Full sun.

I. x norrisii (x Pardancanda norrisii). CANDY LILY. Zones US, MS, LS, CS, TS; USDA 6-11. Group of sun-loving garden hybrids resulting from a cross between Belamcanda (blackberry lily) and Pardanthopsis, an iris relative. To 3 ft. tall, 2 ft. wide. Foliage fans are like those of iris. From midsummer to fall, plants produce six-segmented, 3- to 4-in.-wide flowers in a great range of colors, including yellow, blue, red, purple, pink, white, orange, and bicolors. Each bloom lasts only a day, but new flowers keep the show going. Good cut flowers. Plants are short lived, often blooming themselves to death, but they do self-sow. Grow from seed; in areas where the growing season is long, early sowing results in flowers the first year. Provide regular water and good drainage. Drought tolerant. Dazzler strain offers a variety of colors but on a dwarf plant, growing only 16 in. tall.

I. prismatica. SLENDER BLUE FLAG. Zones US, MS, LS, CS; USDA 6-9. Native to eastern North America. Foliage and flowers suggest a small Siberian iris. Typical form grows about 1 ft. high, bearing dainty purple-and-white blossoms on branching, sinuous stems. A pure white form exists. Give plants full sun and moist (but not boggy), acid soil. Rhizomes spread widely, forming loose colonies rather than tight clumps.

I. pseudacorus. YELLOW FLAG. Zones US, MS, LS, CS; USDA 6-9. Native to Europe but now found worldwide in temperate regions; seeds float, aiding plant's dispersal. Impressive foliage plant; under best conditions, upright leaves may reach 5 ft. tall. Flower stems grow 47 ft. (depending on culture), bear bright yellow flowers 34 in. across. Selected forms offer ivory and lighter yellow flowers, double flowers, variegated foliage, and plants with shorter and taller leaves. Plant in sun to light shade. Needs acid soil and more than average moisture; thrives in shallow water and can become invasive where running water disperses seeds. Ingestion of leaves or rhizomes causes gastric upset. Handling plants causes skin irritations in some people.

Several hybrids are excellent foliage plants with distinctive blossoms. All prefer ample water (but not pond conditions), sun to light shade. 'Holden Clough' perhaps has I. foetidissima as its other parent. Flowers, 34 in. across, are soft tan heavily netted with maroon veins. Stems grow to 4 ft.; leaves reach 45 ft., but tips arch over. Two of its seedlings are similar but larger. 'Phil Edinger' grows to 412 ft. with arching foliage; 4- to 5-in. flowers are brass colored, heavily veined in brown. 'Roy Davidson' is similar, but flowers are dark yellow with ne brown veining and maroon thumbprint on falls.

I. setosa. NORTHERN BLUE FLAG. Zones US, MS, LS; USDA 6-8. Native to Siberia (extending to Kamchatka), Alaska, eastern Canada, and New England. Leaves are a slightly grayed green, 121 in. wide; plants vary from less than 1 ft. to about 2 ft. high, with flower stems taller than leaves. Blooms in late spring and summer, bearing typically blue-purple to red-purple flowers with broadly rounded falls, standards reduced to mere bristles. I. s. nasuensis is larger in all parts than species, reaches about 3 ft. high. Garden culture as for Siberian irises: moist, well-drained, neutral to acid soil; partial or dappled shade. Will grow where buffeted by salt-laden ocean spray. Plant in late summer, early fall.

I. unguicularis (I. stylosa). ALGERIAN IRIS, WINTER IRIS. Zones MS, LS, CS; USDA 7-9. Native to Greece, the Near East, northern Africa. Dense clump of narrow, dark green leaves. Depending on selection and mildness of winter, flowers appear from November to March. Typical form has violet-tinted blue blossoms elevated on 6- to 9-in. tubes that serve as stems. Named selections vary in flower color (lighter and darker lavender, orchid-pink, white) and in coarseness and length of foliage. Plants require neutral to acid soil, heat, and scant water during summer (but will take moderate water if soil is very well drained). In the Middle South, grow against sunny wall or house foundation to increase summer heat and to lessen winter cold. Divide overcrowded clumps in early fall (mild regions) or in late winter after flowering (colder regions). Slugs and snails are attracted to the flowers.

I. versicolor. BLUE FLAG. Zones US, MS, LS, CS; USDA 6-9. Widely distributed North American species, found in bogs and swamps from Mississippi Valley to eastern Canada. Grows 1124 ft. tall; narrow leaves are thicker in the center but not ribbed. Shorter-growing forms have upright leaves, but foliage of taller types may recurve gracefully. The typical wild flowers are a light violet-blue, but lighter and darker forms exist. 'Kermesina' is wine-red. 'Mysterious Monique' is deep violet, almost black. 'Raspberry Slurp' is white with raspberry veins. 'Rosea' is pink. Like I. pseudacorus, this species thrives in sun to light shade, in moist, acid soil or shallow water.

Specialty growers offer hybrids between I. versicolor and other species. Violet-flowered 'Gerald Darby', a hybrid with I. virginica, has striking wine-red stems. Violet-flowered 'Black Gamecock', a hybrid with I. x fulvala, has dark purple blooms.

I. virginica. SOUTHERN BLUE FLAG. Zones US, MS, LS, CS; USDA 6-9. Native to Eastern seaboard, from Virginia south and west to Mississippi River and Gulf Coast. Similar to I. versicolor in form and flower; distinguishing floral feature is longer standards. Flower colors include light to dark blue, wine-red, pink, lavender, and white. A plant sold as 'Giant Blue' is distinctly larger in all parts, approaching I. pseudacorus in size. Plant in moist, acid soil or grow in shallow water. In deep ponds, plant in large pots barely submerged beneath the surface. Full sun or light shade.

CRESTED IRISES. Though these are botanically placed with beardless irises, they represent a transition between beardless and bearded: Each fall bears a narrow, comblike crest where a beard would be in bearded sorts. Slugs and snails are especially attracted to foliage and flowers.

I. cristata. CRESTED IRIS. Zones US, MS, LS, CS; USDA 6-9. Native to South except for Florida, Louisiana, and Texas. Leaves 46 in. long, 12 in. wide; slender greenish rhizomes spread freely. White, lavender, or light blue flowers with golden crests. 'Powder Blue Giant' can reach 8 in. tall; its light blue flowers are almost 3 in. across. Give light shade, organically enriched soil, regular water. Divide just after bloom or in fall after leaves die down.

I. tectorum. ROOF IRIS. Zones US, MS, LS, CS; USDA 6-9. Native to Japan, where it is planted on cottage roofs. Foliage fans to 1 ft. tall look like those of bearded irises, but light green leaves are ribbed and glossy. Foliage looks good all summer. Flowers suggest an informal bearded iris with fringed petals and crests in place of beards. Blooms are violet-blue with white crests; standards are upright at first, opening to horizontal as flower matures. 'Alba' has white petals with yellow-throated crests. 'Wolong' forms tight clumps; flowers are lavender with a white crest surrounded by dark purple flecks.

Provide organically enriched soil, light shade, and regular water. Good companion for hostas. Short lived in regions where summers are hot and dry. 'Paltec', a hybrid of I. tectorum with a bearded iris, will grow with bearded irises; it reaches about 1 ft. high, with lavender flowers suggesting a bearded iris with beards superimposed on crests.

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