Family: Asteraceae

Origin, Description & Uses
Pluchea carolinensis (sourbush, cure-for-all) is native to tropical and subtropical regions of the Americas. It is a fast-growing, aromatic shrub in the sunflower family that typically reaches several feet in height and produces small, fuzzy leaves and clusters of pinkish to whitish flower heads. The plant is sometimes recognized for its strong scent and has been traditionally used in parts of its native range for medicinal purposes, where it has been applied as a general “cure-all” herbal remedy for various ailments.

Risks & Threats
In Hawai‘i, Pluchea carolinensis is naturalized and widely established, occurring in relatively dry coastal areas as well as extending into mesic to wet forests up to about 900 m elevation. It is found on all main Hawaiian Islands as well as on several remote atolls, including Kure Atoll, Midway Atoll, and French Frigate Shoals, and was first collected on O‘ahu in 1931. This species is naturalized, possesses traits that are cause for concern, and could detrimentally impact tropical island ecosystems. It spreads readily and can form dense stands that crowd out native vegetation, particularly in coastal and disturbed habitats, altering habitat structure and reducing biodiversity. Its ability to disperse widely and establish in a range of environments makes it a management concern for sensitive island ecosystems.

High Risk Traits:

• Thrives in tropical climates
  
• Widely naturalized
  
• A pasture and environmental weed, threatening endangered plant taxa in the Hawaiian Islands
  
• Other Pluchea species have become invasive
  
• Possibly unpalatable or of low forage value
  
• Forms dense thickets, excluding other vegetation
  
• Tolerates many soil types
  
• Reproduces by seed
  
• Hybridizes with invasive Pluchea indica
  
• Seeds dispersed by wind and accidentally due to human activity and movement of materials, equipment etc.
  
• Prolific seed production (densities unknown)
  
• Able to resprout from roots after die-back after fires
  
• No effective biological control agents present in the Hawaiian Islands. None known elsewhere

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Non-toxic, with medicinal uses
  
• Shade-intolerant
  
• Not reported to spread vegetatively (but able to resprout)
  
• Herbicides provide effective control