Dietes iridioides
Common Name: dietes
Type: Herbaceous perennial
Family: Iridaceae
Native Range: Southern and eastern Africa
Zone: 9 to 11
Height: 2.00 to 4.00 feet
Spread: 2.00 to 3.00 feet
Bloom Time: May to September
Bloom Description: White with yellow and blue markings
Sun: Full sun to part shade
Water: Medium
Maintenance: Medium
Suggested Use: Annual
Flower: Showy

Culture

Winter hardy to USDA Zones 9-11 where plants may easily be grown in moist, moderately fertile, well-drained soils in full sun to part shade. In St. Louis, plants may be grown as annuals (rhizomes may be dug up before first fall frost for overwinter storage in peat or vermiculite at 45F) or in containers that may be overwintered indoors. Best flowering occurs in full sun, but plants may appreciate some part light afternoon shade. Plants tolerate some soil dryness, but are best grown with regular moisture. Remove seed pods as they begin to form to encourage additional bloom. Flower stems should not be removed after bloom. Clip off any leaves that die. Propagate by seed or division of the rhizome.

Noteworthy Characteristics

Dietes iridioides, commonly called African iris, comes from eastern and southern Africa. It is a rhizomatous evergreen perennials that generally resemble beardless iris and grows 2-4’ tall. It produces fan-shaped clumps of iris-like, narrow, sword-shaped, basal, evergreen leaves. Flowers appear on branched stalks. In frost-free areas, plants bloom spring to fall and intermittently throughout winter. Flowers last one day, but are quickly replaced. Each flower (to 3” wide) is white with yellow and blue markings. Each flower stalk carries a large supply of buds. Flowering occurs in bloom bursts that often occur at 2 week intervals, hence the sometimes used common name of fortnight lily (though it is not a lily). Fruit is an obovoid capsule. In the iris family, Iris is native to temperate regions of the Northern Hemisphere and Dietes is native to certain frost-free areas of the Southern Hemisphere (five species from Africa and one species from Lord Howe Island east of Australia). At one point, Dietes was considered to be part of the genus Moraea, but the two genuses were separated in large part because Dietes grows from a rhizome and Moraea from a corm. Dietes iridioides is synonymous with Dietes vegeta and Moraea iridioides.

Genus name comes from dis meaning double.

Specific epithet means resembling iris.

Problems

No serious insect or disease problems. Crown root, root rot and rust may occur. Scale and nematodes.

Garden Uses

Where winter hardy, these plants are popular landscape plants that are often massed in low maintenance garden areas. They have long-blooming accent value. In St. Louis, plants are best grown as annuals or in greenhouses, conservatories or in containers placed outside during frost free months.