Family: Asteraceae

Origin, Description & Uses:
Sigesbeckia orientalis, commonly known as St. Paul’s wort or Oriental St. Paul’s wort, is an annual herb native to a broad region extending from tropical Africa and islands of the western Indian Ocean through Asia and into Australia. It grows upright, typically reaching 1–2 meters in height, with branching stems, opposite leaves, and small yellow flower heads. The plant thrives in disturbed habitats, roadsides, agricultural lands, open forests, and moist waste areas. In parts of its native and introduced range, it has been used in traditional medicine and is sometimes valued for its purported anti-inflammatory and herbal properties.

Risks & Threats:
Sigesbeckia orientalis is naturalized across the Hawaiian Islands, including Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi Island, where it occurs from low elevations to over 1,200 meters. This species possesses traits that are cause for concern, including rapid growth, prolific seed production, and an ability to readily colonize disturbed environments. These characteristics allow it to spread into agricultural areas, roadsides, pastures, and natural ecosystems, where it can compete with native vegetation and contribute to changes in plant community structure. Because it is already widespread in Hawaiʻi, efforts should focus on managing existing populations and preventing its use or further spread into areas where it is not yet well established. As a naturalized species with the potential to detrimentally impact tropical island ecosystems, Plant Pono recommends choosing low-risk or native alternatives whenever suitable options are available.

High Risk Traits:

• Broad climate suitability (tropical to warm temperate, 0–2100 m)
  
• Naturalized outside native range (Pacific Islands, Australia, etc.)
  
• Environmental weed (e.g., Southeast Queensland)
  
• Shade tolerant
  
• Tolerates wide range of soil conditions
  
• Produces viable seed
  
• Short generation time (annual; up to 2 generations/year)
  
• Unintentional dispersal (sticky seeds adhere to clothing, skin, fur)
  
• Intentional dispersal (widely used in traditional medicine)
  
• Water-dispersed seeds
  
• Animal-dispersed seeds (external attachment)
  
• Persists and germinates after fire

Low Risk Traits:

• No spines, thorns, or burrs
  
• Not toxic to humans (used medicinally)
  
• No vegetative reproduction (seed only)