Venice Mallow

Hibiscus trionum

Keys to Identification

Leaves are palmately compound, have 5-7 toothed leaflets, and somewhat resemble a marijuana leaf.
Light-yellow flowers have five petals that are deeply notched.
Leaf stalks have perpendicular hairs longer than the width of the stalk.

This information courtesy of the Colorado Natural Areas Program

Family: Malvacaea (Mallow)

USDA Code: HITR

Legal Status: Colorado Noxious Weed List B

Identification

Lifecycle: Annual

Forb

Flower: Flowers are a light sulfur-yellow color with a red to purple center. Flowers only last a couple of hours, hence the nickname, “flower of an hour”.

Seeds/Fruit: Seeds are dark brown and can remain dormant for 50 years.

Leaves: Alternate, divided into 3 to 5 distinct lobes. Margins on the lobes are toothed.

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

Roots: Shallow taproot with a fibrous system.

Seedling: Cotyledons are round with hairy petioles. First true leaves have toothed margins and are alternate.

Impacts

Ecological: Primarily a weed of nurseries, orchards, roadside fields, and open waste areas.

Habitat and Distribution

General requirements: Venice mallow is drought tolerant, can grow in acidic soils and in gravely soils.

Distribution: Throughout the U.S.

Historical: Introduced from Europe .

References

Whitson, T.D.(ed.), L.C. Burrill, S.A. Dewey, D.W. Cudney, B.E. Nelson, R.D. Lee, R. Parker. 5th Edition 1999. Weeds of the West. Western Society of Weed Science, in cooperation with the Western United States Land Grant Universities Cooperative Extension Services, Newark CA

Westra, P., C. H. Pearson, R. Ristau, and F. Schweissing. 1996. Venice mallow (Hibiscus trionum) seed production and persistence in soil in Colorado. Weed Tech. 10:22-28.

Westra, P., C. Pearson, and R.J. Ristau. 1990. Control of Venice Mallow (Hibiscus trionum) in Corn (Zea mays) and Onions (Allium cepa). Weed Tech. 4:500-504.

CWMA