Venice Mallow is a summer annual broadleaf weed that is also commonly known as Flower of an Hour, Bladder Ketmia, Modesty and Shoo-fly. Its scientific name is Hibiscus trionum.
Venice Mallow is a broadleaf weed with three (or sometimes five) lobed leaves that can be deeply cut. Its stems are usually branched at the base, spreading to erect, hairy tips. The leaves are larger toward the apex, forming on long petioles, and are reduced in size near the top of the plant. Blooming from June through September, Venice Mallow develops remarkable flowers with pale-yellow to white-colored petals and deep-purple bases. There are multiple stamens in the center with brilliant yellow anthers. The flowers are open for only a few hours each morning, hence the nickname Flower of an Hour. Reproduction occurs by seeds.
This broadleaf weed prefers waste areas and often grows in fields, unkept lawns and along railroads and roadsides. Venice Mallow can be found throughout most of the continental United States, with the exception of Mississippi and Nevada.
Hibiscus trionum is a difficult weed to control in lawns, gardens, nurseries and orchards. Its seeds can remain dormant underground for several decades, making this weed immune to many cultural weed control methods such as proper mowing or core aeration. Professionally selected and applied broadleaf weed killers—based on your specific climate and geography—are the most effective method for control.