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Weed Identification

Virginia Tech College of Agriculture and Life Science Virginia Cooperative Extension

flower of an hour

Family

Malvaceae

Scientific Name

Hibiscus trionum
Weed photograph 1
Weed photograph 2
Weed photograph 3
Weed photograph 4
Weed photograph 5
Weed photograph 6

Other Common Names:

bladder ketmia
shoo-fly
Venice mallow
modesty
rose mallow

Synonyms (former Scientific Names):

Trionum trionum

Leaves

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

Identifying Characteristics

A summer annual with divided leaves and showy yellow and purple flowers.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.

Flower Seed Head

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.

Seed Fruit

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. fruit is A round, hairy capsule that is surrounded by the sepals.

Where Found

Venice mallow is primarily a weed of agronomic and nursery crops that is found throughout the eastern half of the United States.

Growth Habit

Varies: 
upright and nonwoody, 
prostrate and nonwoody

Thorns or Spines

not present

Approximate Flower Diameter

Varies: 
dime, 
nickle, 
quarter, 
half dollar

Dominant Flower Color

Varies: 
white, 
yellow, 
purple

Flower Symmetry

radial symmetery

Leaf Hairs

has hairs

Leaf Shape

Varies: 
round, 
spatulate, 
triangle

Leaf Arrangement

alternate

Leaf Margin

Varies: 
lobed, 
serrated

Leaf Structure

palmate

Leaf Stalk

Varies: 
shorter than leaf, 
longer than leaf

Stem Hairs

has hairs

Stem Cross Section

round or oval

Milky Sap

not present

Root Structure

taproot

Life Cycle

summer annual

Ochrea

not present

Plant Type

Herb