Common Name: iris
Type: Herbaceous perennial
Family: Iridaceae
Zone: 4 to 9
Height: 2.00 to 3.00 feet
Spread: 1.50 to 2.50 feet
Bloom Time: May to June
Bloom Description: Violet blue
Sun: Full sun to part shade
Water: Medium to wet
Maintenance: Low
Suggested Use: Water Plant, Naturalize
Flower: Showy
Leaf: Colorful
Tolerate: Deer
Culture
Grow in medium to wet soils in full sun to part shade. This iris may be grown in 2-4” of shallow standing water (muddy bottom or containers), or in moist shoreline soils or in moist sandy-humusy border soils. Border soils must not be allowed to dry out. Propagate by division after bloom. Wear gloves when dividing the rhizomes. After fall frost, plant leaves may be trimmed back to about 1” above the crown.
Noteworthy Characteristics
Iris × robusta is a designation for hybrids of two native American irises (Iris versicolor × Iris virginica). This hybrid forms a clump of narrow, arching-to-erect, sword-shaped, green leaves (to 24” long). Leaves have a flush of purple in spring that fades by summer. Leaves are also spotted with purple-red at the base. Purplish-black flowering stalks rise from the clump to 36” tall in late spring, typically producing 2-3 violet-blue flowers per stalk. Clumps spread slowly by tough, creeping rhizomes. The rhizomes of this plant are poisonous.
Genus named for the Greek goddess of the rainbow.
Hybrid name means robust or strong in growth.
‘Gerald Darby’ is a marginal aquatic hybrid cultivar that is noted for its attractive violet-blue flowers and variegated spring foliage.
Problems
No serious insect or disease problems. Susceptible to a number of insect pests including aphids, iris borer and iris thrips. Susceptible to a number of diseases including various rots and viruses.
Uses
Best grouped in sunny areas of ponds or water gardens. Also may be grown in moist border areas.