Invasive

Urena lobata

Caesar's Weed

Introduction

Origin: India and tropical Asia

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.

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.

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.

Management Plan


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.

Cultural

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

Mechanical

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

Biological

No known biological controls for this species.

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%.