- Pest Type: Weed
- Crops Affected: Wheat, Cotton, Potatoes, Soybeans, Corn
- Scientific Name: Hibiscus trionum
- Pest Order: Malvaceae
Venice mallow is a summer annual with 3- or 5-lobed or deeply cut leaves, each with rounded teeth or lobes on the margins. Stems are usually branched at the base, spreading to erect (20-50 cm tall).
Reproduction is by seed; seedlings may emerge throughout the summer, particularly after cultivation. Seeds persist in the soil, remaining dormant for many years.
Hypocotyls are stout and hairy. Cotyledon leaves are yellow-green, thick, rounded or heart-shaped. Cotyledon petioles are hairy and longer than the blades. The first two leaves are toothed and irregular in shape; subsequent leaves are deeply 3-lobed.
Young leaves are alternate. Leaf blades are densely hairy below and sparsely hairy above.
Stems are hairy, branching near the base to form a tuft. Leaves are alternate, about 7.5 cm long and wide, and deeply 3-lobed or sometimes 5-lobed; each lobe has coarse rounded teeth or small lobes. Leaves are oblong to egg-shaped, larger toward the apex, on long petioles subtended by two stipules. Leaves are reduced near the top of the plant.
Fibrous root system with a shallow, weak taproot.
Flowers are present from July to September, opening only for a few hours each day in the morning. Flowers are subtended by several linear bracts and are produced singly or in groups of 2 or 3 in the upper leaf axils. Sepals are pale green with dark green veins and are fused into an inflated membranous bladder. Petals (5) are 1.5-4 cm long, pale yellow to white, with purple bases. Stamens are united into one column; the filaments are dark purple, and the anthers are yellow-orange. The fruit capsule contains about 30 seeds and is enclosed within the expanded bladder. Seeds are about 2 mm long, kidney-shaped to triangular, rough, and dark brown to grayish black. Seeds have small star-shaped hairs on the surface.
These plants do not persist after frost. The distinctive seedheads remain attached for only a short time.
Venice mallow is a weed of nursery, horticultural, and agronomic crops. It is most common in cultivated areas, it tolerates drought, gravel, and alkaline soils.
Venice mallow is a common weed in the eastern half of the United States, particularly in the southeastern and Midwestern states.
Musk mallow has similar foliage, but its leaves are 5-7 parted, whereas Venice mallow leaves are 3-parted. In addition, the basal leaves of musk mallow are rounded and lobed, while those of Venice mallow are dissected.