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Fortnight Lily, African Iris

These irislike plants with fans of stiff, narrow evergreen leaves form dense, long-lasting clumps. The flowers, resembling small Japanese irises, consist of three outer and three inner segments. They appear on branched stalks throughout spring, summer, and fall, sometimes well into winter in mild climates. Bloom bursts seem to occur at 2-week intervals, hence the common name “fortnight lily.” The flowers come in solid colors—white, cream, yellow; each of the three outer segments features a small blotch of contrasting orange, yellow, or brown. Each flower lasts only a day (with the exception of D. grandiflora), but the supply of flowers on a stem is seemingly endless. Excellent in permanent landscape plantings with pebbles and rocks, shrubs, and other long-lived perennials.

Plant from containers (bare rhizomes are not sold) at any time of year, setting plants about 2 ft. apart. All types look best with good soil and regular watering; but once established, they will perform satisfactorily even in poor soil or with infrequent or erratic watering. Clumps can remain undisturbed for years; when you need to divide, do so in fall or winter.

Dietes grandiflora (photo courtesy of David Cavagnaro)
Dietes grandiflora (photo courtesy of David Cavagnaro)

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Dietes grandiflora

From South Africa. This is a somewhat taller (up to 3 ft.), larger version of D. iridioides and is usually sold as a variety of that species. Other differences include brown markings at the bases of inner segments and, on outer segments, yellow blotches that are actually bearded. Unlike all the others, this species has flowers that last for 3 days before folding; flower stems are perennial (see D. iridioides). ‘Variegata’ has dull green leaves with creamy yellow margins. ‘Sunstripe’ has yellow-striped leaves.

Dietes iridioides

Native to East Africa. Stems to 3 ft. tall. Waxy white flowers to 3 in. across have yellow-orange blotches, a few orange marks at bases of inner three segments; three style arms—appendages radiating from flower’s center—are usually pale violet. To prevent self-sowing and prolong bloom, break off blossoms individually. Don’t cut flower stems (they last for more than a year) until they clearly have stopped producing blooms; then cut back to lower leaf joint near base of stem.

‘John’s Runner’ is a dwarf form growing only 1–2 ft. high and 2–3 ft. wide with white flowers marked with yellow and purple. Spent flower stalks produce plantlets that root as the stalks fall over, allowing the plant to spread. For the plant sold as D. iridioides ‘Johnsonii’, see D. grandiflora.


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