Virginia Tech Weed Identification Guide

Venice Mallow: Hibiscus trionum

Weed Description:  A summer annual with divided leaves and showy yellow and purple flowers.  Venice mallow is primarily a weed of agronomic and nursery crops that is found throughout the eastern half of the United States.
Seedling: Cotyledons are round and occur on long hairy petioles.  First true leaves are alternate and irregularly shaped with a toothed margins.  All subsequent leaves are lobed at least 3 times. vmallow3-19b.jpg (173705 bytes)
vmallow5-2.jpg (140187 bytes) Leaves:  Alternately arranged along the stem and are approximately 3 inches wide and long.  Leaves are divided into at least 3 distinct lobes, but may be divided into as many as 7 lobes.  All lobes have margins that are toothed.  All leaves occur on long petioles and are without hairs (glabrous) on the upper surface and have hairs on the lower surface.

Stems:  Erect, hairy, and branching from the base.

Roots: A shallow taproot and a fibrous root system.

Flowers: Arise from the position between the stem and leaf petioles (leaf axils).  Flowers consist of 5 petals that are pale yellow to white in color with a purple base.  The 5 sepals resemble a membranous bladder with distinctive dark green veins. vmallow4-5.jpg (79056 bytes)
vmallow4-5b.jpg (139864 bytes) Fruit: A round, hairy capsule that is surrounded by the sepals.
Identifying Characteristics:   The lobed leaves, membranous sepals that resemble a bladder, and yellow and purple flowers are all characteristics that help in the identification of Venice mallow. vmallow5-2b.jpg (83896 bytes)