Family: Malvaceae

Origin, Description & Uses:
Triumfetta semitriloba, commonly known as burweed or Sacramento-bur, is a fast-growing shrub native to tropical and subtropical regions of the Americas. It typically grows 3–10 feet (1–3 m) tall and produces soft, heart-shaped to triangular leaves and small yellow flowers that develop into distinctive round burs covered with hooked spines. These burs readily cling to clothing, animal fur, and equipment, aiding in seed dispersal. Although not widely cultivated as an ornamental, the species has been used locally for fiber, traditional medicine, and erosion control, and it commonly colonizes roadsides, abandoned fields, forest edges, and other disturbed areas.

Risks & Threats:
Triumfetta semitriloba is naturalized on Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi Island, where it is often common in dry, disturbed habitats from approximately 30–860 m elevation. It possesses traits that are cause for concern, including rapid growth, prolific seed production, and highly effective dispersal by its hooked burs, which attach to people, livestock, wildlife, and vehicles. These characteristics allow it to spread readily into new areas, where it can form dense stands that compete with native vegetation and hinder restoration efforts, potentially impacting tropical island ecosystems. Because this species is already widespread in Hawaiʻi, landowners and landscapers should avoid planting or intentionally spreading it and should manage existing populations to prevent further expansion into areas where it is not yet well established. Whenever possible, choose a low-risk or native alternative for landscaping, erosion control, or habitat restoration.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Thrives in tropical climates
  
• Naturalized on Kauai, Oahu, Maui, and Hawaii, Molokai and elsewhere
  
• Pasture weed, displacing more valuable forage plants
  
• Environmental weed, threatening rare and endangered species in the Hawaiian Islands
  
• Other Triumfetta species are invasive
  
• Burrs covered with hooked bristles
  
• Little or no forage value
  
• Tolerates many soil types
  
• Reproduces by seeds
  
• Self-compatible
  
• Able to reach reproductive maturity in 6 months
  
• Burrs attach to clothing and fur and disperse seeds
  
• Prolific seed production

Low Risk Traits:

• Requires disturbance for establishment
  
• Non-toxic
  
• Not reported to spread vegetatively
  
• Herbicides provide effective control
  
• Effectively controlled by uprooting, plowing, or burning