Dietes bicolor
Common Name: butterfly flag
Type: Bulb
Family: Iridaceae
Native Range: South Africa
Zone: 9 to 11
Height: 1.50 to 2.00 feet
Spread: 0.75 to 1.00 feet
Bloom Time: May to September
Bloom Description: Light yellow with dark brown tepal blotches
Sun: Full sun to part shade
Water: Medium
Maintenance: Low
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. Cut each flower stem to the ground after flowering is completed. Propagate by seed or division of the rhizome.

Noteworthy Characteristics

Dietes belongs to the iris family. Genus plants are rhizomatous evergreen perennials that generally resemble beardless iris. Dietes bicolor comes from South Africa, and is often commonly called African iris. 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 from spring to fall and intermittently throughout winter. Flowers last one day, but are quickly replaced. Each flower (to 2” wide) has three light yellow tepals with dark brown blotches at the bases and three petal-like staminoids that lack blotches. 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). Plants generally grow to 2’ tall. 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 comes from Greek words that mean “with two relatives” in reference to the relationship of this plant to Iris and Moraea. Bicolor means having two colors.

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.