India and tropical Asia
Widely naturalized and considered a “serious threat” in hardwood hammocks and roadsides in south Florida by 1976 (Morton 1976). Reported from over 100 conservation areas in central and south Florida (Gann et al. 2001, FLEPPC 2002). Forms thickets, and is often abundant on swamp edges and in wet woodlands (Godfrey and Wooten 1981).Declared a noxious weed in Fiji and Hawaii (PIER 2002).
Tough, erect, woody perennial herb or sub-shrub, to 3 m (10 ft), but usually to 1.5 m (5 ft); stems and leaves covered with star-shaped hairs; often many branched at base. Leaves simple, alternate, papery, upper surface rough, lower surface grayish, broadly ovate, often with 3-5 shallow, angular lobes at apex, to 10 cm (4 in) long; margins finely toothed, bases heart shaped; petioles to 5 cm (2 in) long; stipules tiny, linear. Flowers small, showy, hibiscus-like, solitary on short stalks in leaf axils, subtended by 5 basally united (involucral) bracts to 0.7 cm (0.3 in); calyx 5-lobed, hairy, to 0.6 cm (0.2 in); petals 5, rose or pink, darker at base, rounded, to 1.5 cm (0.6 in) long; stamens fused into an obvious pink column beneath a 5-lobed style. Fruit a small, barbed, spiny capsule, to 1 cm (0.4 in) across, with 5 prominent segments each containing 1 dark brown seed (K.A. Langeland, H.M. Cherry, et al, 2008).
Caesar weed is an erect shrub that grows up to 10 feet in height. May occur as scattered plants but can quickly spread to form dense patches and, occasionally, monocultural stands (FLEPPC 2002). Widespread throughout peninsular Florida in almost all habitat types, including hammocks, disturbed sites (Wunderlin 1998, Austin 1999b), pine flatwoods, sandhills, river edges, maritime forests, salt marshes, and coastal dunes (FLEPPC 2002).
Introduced to Florida before 1895 and “escaped to waste places” before 1897 (Chapman 1897, Parsons 1895). Distributed extensively as a fiber crop and for its many medicinal uses (Austin 1999b). Nectary glands on underside of leaves are used as a food source in Florida by native and nonnative ants (Dreisig 2000).
Herbarium specimens documented from 36 counties in Florida (K.A. Langeland, H.M. Cherry, et al, 2008). Species mostly concentrated in central and south Florida.
Mechanical: Shade will help to deter growth and limit seedling establishment. Mulches or other ground cover will also prevent seed germination. Chemical: Limited research in this area, but triclopyr (Remedy) will probably be more effective than glyphosate (based on research with cotton). Use 1-2% solution with surfactant at 0.25% (Center for Aquatic and Invasive Plants).