Caesar Weed

Urena lobata

Caesar's Weed

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Introduction

There are many plants in the family Malvaceae that are grown for ornamental purposes including Hibiscus, Abutilon, Alcea. Cotton (Gossypium hirsutum) is also in this family. Not only does this plant family contain many ornamentals, but there are also many weedy species such as Malva, Malachra, and Urena.

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Description

Caesar weed is an erect shrub that grows up to 10 feet in height. The plant is single stalked, with free-branching stems that comprise a bushy appearance. The leaves are palmately lobed, pubescent with stellate hairs, and 4-8 cm long. Flowers are borne in axillary clusters, pinkish-violet, about 1 cm across. Fruit is pubescent with hooked bristles or barbs that cling to clothing or fur. It grows as an annual species in many areas of Florida but may perennate in south Florida.

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Impacts

Caesar weed invades disturbed areas, pastures, eroded areas, and perennial crop plantations. The species does not compete well in tall grass and brush lands and does not grow under forest canopies. Caesar weed tolerates salt spray but does not grow in saturated soils. Having an aggressive habit, Caesar weed grows rapidly and can reach 2 to 7 feet by the end of the first year.

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Management

 

Preventative:

Care should be taken to prevent seed spread into ‘clean areas’. The seed of Caesar weed clings to clothing, therefore treat plants before seed set. Avoid treating areas of this species and then travel to other areas. Also avoid driving vehicles through areas of Caesar weed.

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Cultural:

Shade will help to deter growth and limit seedling establishment. Mulches or other ground cover will also prevent seed germination.

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Mechanical:

Shade will help to deter growth and limit seedling establishment. Mulches or other ground cover will also prevent seed germination.

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Biological:

No known biological controls for this species.

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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%.

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References and Useful Links:

Floridata Homepage

University of Florida Center for Aquatic and Invasive Plants

University of Florida’s Cooperative Extension Electronic Data Information Source

Langeland, K.A. and K. Craddock Burks. 1998. Identification and Biology of Non-Native Plants in Florida's Natural Areas. IFAS Publication SP 257. University of Florida, Gainesville. 165 pp.

The Plant Conservation Alliance's Alien Plant Working Group. Weeds Gone Wild: Alien Plant Invaders of Natural Areas

Pacific Island Ecosystems at Risk (PIER). Plant Threats to Pacific Ecosystems

Invasive Plants of the Eastern United States

USDA Natural Resources Conservation Service. Plants Database

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Excerpted from the University of Florida, IFAS Extension, Circular 1529, Invasive Species Management Plans for Florida, 2008 by:

Greg MacDonald, Associate Professor Jay Ferrell, Assistant Professor and Extension Weed Specialist
Brent Sellers, Assistant Professor and Extension Weed Specialist
Ken Langeland, Professor and Extension Weed Specialist Agronomy Department, Gainesville and Range Cattle REC, Ona
Tina Duperron-Bond, DPM – Osceola County
Eileen Ketterer-Guest, former Graduate Research Assistant

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