Hibiscus trionum

Common Name: flower of an hour 
Type: Annual
Family: Malvaceae
Native Range: Arid Old World Tropics
Zone: 2 to 11
Height: 1.50 to 2.00 feet
Spread: 1.50 to 2.00 feet
Bloom Time: June to October
Bloom Description: White to pale yellow with dark centers
Sun: Full sun
Water: Medium
Maintenance: Low
Suggested Use: Annual
Flower: Showy
Tolerate: Deer


Easily grown in organically rich, medium moisture, well-drained soils in full sun. Performs well in average garden soils. It the St. Louis area, it is best to start seed indoors about 8-10 weeks before the last spring frost date. Seeds may be planted directly in the garden at last frost date, but will take up to three months before first flowering occurs.

Noteworthy Characteristics

Hibiscus trionum is sometimes commonly called flower-of-an-hour because its white flowers will bloom for only a few hours before wilting. Native to Europe, this annual has naturalized over time by self-seeding throughout much of the U. S. where it is often now found along roadsides, railroad tracks, in waste areas and in open fields. It can be weedy in some areas. It grows to 2’ tall on branching stems clad with long-stalked, palmately divided, coarsely-toothed, dark green leaves (to 3” long) in three (infrequently five) parts. Lower leaves may be entire. Solitary white to pale yellow flowers (to 2” across) with dark purple centers bloom from the leaf axils from summer to frost. Flowers give way to bladder-like seed pods. This plant is also commonly called Venice mallow.

Genus name is the old Greek and Latin name for mallow.

Specific epithet means three parted in reference to plant leaves.


No serious insect or disease problems.


Beds, borders, cottage gardens. Containers.