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IRIS


377


Iris


Iridaceae PERENNIALS FROM BULBS AND RHIZOMES


ZZONES VARY ACCORDING TO SPECIES OR TYPE


FPSEXPOSURE NEEDS VARY BY SPECIES


DOW WATER NEEDS VARY BY SPECIES


X TOXIC KINDS NOTED IN ENTRIES


fall planting, plus a few contain- erized irises during bloom sea- son, and often plants from the Pacifi c Coast, Siberian, and Jap- anese iris groups.


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


Dutch and Spanish irises


Siberian iris ‘Caesar’s Brother’


Named for the Greek rainbow goddess and stylized as the fl eur-de-lis, irises typically have grassy or swordlike foliage and fl ower parts in threes. A remark- ably diverse group of more than 250 species, these vary in fl ower color and form, cultural needs, and blooming periods (although the majority fl ower in spring or early summer). Flow- ers, often fragrant, are showy and complex. The three inner segments (the standards) are petals; they are usually erect or arching but, in some kinds, may fl are to horizontal. 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. Flowers are grouped into three broad categories: bearded (each of the falls bears an adornment resembling a fuzzy caterpillar); beardless (falls are smooth); and crested (falls have a comblike ridge instead of a full beard). Tall bearded irises (and other bearded classes) are the most widely sold; many new hybrids are cataloged every year. A smaller number of growers offer various beardless classes and some species. Retail nurseries usually carry bulbous irises for


Zones 2b–24. The parent spe- cies of this group come from Spain, Portugal, Sicily, and northern Africa. (Dutch irises are named for the Dutch bulb growers who hybridized them. They are often sold as I.× hol- landica varieties.) Flowers are borne atop slender stems that rise from rushlike foliage. Stan- dards are narrow and upright; oval to circular falls project downward. Colors include white, mauve, blue, purple, brown, orange, yellow, and bicolor com- binations—usually with a yellow blotch on falls. Dutch iris fl ow- ers reach 3–4 in. across, on stems 11⁄2–2 ft. high; these are the irises sold by fl orists. Bloom period is early spring in warm- winter climates, late spring in colder areas. Spanish irises are similar but have smaller fl owers that bloom about 2 weeks after Dutch irises.


Plant bulbs in autumn, set- ting them 4 in. deep, 3–4 in. apart; give full sun. Bulbs are hardy to about –10°F (–23°C), but in coldest adapted zones, apply a mulch in winter. Give regular water during growth. Bulbs can be left in the ground for several years where sum- mers 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 2 months before replanting. Dutch and Spanish irises are good in con- tainers; plant fi ve bulbs in a 5–6-in. pot.


The widely sold ‘Wedgwood’ is a Dutch hybrid hardy only in Zones 4–24. Large fl owers are lavender-blue with yellow mark- ings, blooming earlier than oth- ers (generally coinciding with early midseason daffodils). Bulbs are larger than those of


average Dutch hybrid. Vigorous foliage dies down after bloom and is best masked by bushy annuals or perennials that mature later in the season.


English irises Zones 3–6, 15–17, 21–24. The species (I. latifolia) from which named selections were made is native to the Pyrenees, where it grows in moist meadows. Early botanists fi rst noticed the iris growing in southern England, where it had been brought by traders. Flowers are similar in structure to Dutch and Spanish irises, but falls are broader and decorated with a hairline stripe of yellow. Colors include bluish purple, wine red, maroon, blue, mauve, white. Bloom comes in early summer. Plant bulbs in fall, 3–4 in. deep, 4 in. apart, in cool, moist, acid soil. Choose a partly shaded location in warm- summer areas, full sun where summers are cool. Because English irises don’t need com- plete dryness after fl owering, they can be left in the ground in suitable climates. Bulbs are hardy to about –10°F (–23°C). Or the bulbs can be lifted and replanted.


Reticulata irises Zones 3–24; safer in containers in colder zones. The netted (“reticulate”) outer covering on the bulbs gives the group its name. These are classic rock garden and container plants, the fl owers (like small Dutch irises) appearing on 6–8-in. stems in very early spring (mid- winter in mild areas). Narrow blue-green leaves appear after bloom. The available species include I. reticulata, with 2–3-in.


violet-scented fl owers (purple, in the usual forms), and bright yellow– fl owered I. danfordiae. Large-fl owered, blue-and-yellow I. histrioides is carried by some specialists. Far more common are named hybrids such as ‘Cantab’ (pale blue with orange markings), ‘Harmony’ (blue marked in yellow), and ‘ J. S. Dijt’ (reddish purple). Bulbs are hardy to about –10°F (–23°C) and need some subfreezing winter temperatures to thrive. Plant in autumn, in well-drained soil in a sunny loca- tion; set bulbs 3–4 in. deep and 3–4 in. apart. Need regular moisture from autumn through spring. Soil should be kept dry during summer dormant period; in rainy climates, lift bulbs in summer or grow in pots so that you can control moisture. Divide only when vigor and fl ower qual- ity deteriorate. Watch for slugs and snails.


RHIZOMATOUS IRISES


Irises that grow from rhizomes (thickened, modifi ed stems with fl eshy roots) may have bearded, beardless, or crested fl owers; among this group are the most widely grown types. Leaves are swordlike, overlapping one another to form fl at fans of foliage.


Bearded irises Zones 1–24. The most widely grown irises fall into the bearded group. More than a century of breeding has pro- duced a vast array of beautiful hybrids. All have upright stan- dards and fl aring to pendent falls that have characteristic epaulettelike beards. Tall


Refresh Crowded Irises


When clumps of rhizomatous irises become over- crowded after 3 or 4 years, the quantity and quality of blooms decrease. Lift and divide crowded clumps at best planting time for your area. Save large rhi- zomes with healthy leaves; discard old and leafl ess 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 before replanting. If replanting in the same soil, amend it with organic matter.


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