Family: Verbenaceae

Origin, Description & Uses
Stachytarpheta mutabilis, commonly known as changeable porterweed, is a flowering shrub native to Mexico, Central America, and tropical regions of the Americas. It typically grows 3–10 feet (1–3 m) tall and produces long, slender flower spikes bearing colorful blooms that may vary in shades of pink, purple, red, or lavender. The plant flowers over an extended period and is highly attractive to butterflies, bees, and other pollinators. Because of its showy flowers and ease of cultivation, it has been widely planted as an ornamental in tropical and subtropical landscapes.

Risks & Threats
This species is naturalized on Kauaʻi and possesses traits that are cause for concern in Hawaiʻi. Stachytarpheta mutabilis produces abundant seeds, can spread beyond cultivation, and is capable of establishing in disturbed areas, roadsides, forest edges, and other natural habitats. Dense populations may compete with native vegetation for space, light, and resources, potentially altering plant communities and ecological processes. Because it is already naturalized and has demonstrated the ability to spread, it could detrimentally impact tropical island ecosystems if its distribution continues to expand. When selecting plants for landscaping, choose low-risk or native alternatives whenever available. In areas where this species is already widespread, avoid planting it near natural areas and manage existing populations to help prevent further spread and minimize negative environmental impacts.

High Risk Traits:

• Naturalized in Hawaii and elsewhere.
  
• Naturalized on Kaua'i
  
• Agricultural weed (pastures, sugarcane in Australia).
  
• Closely related species are serious weeds.
  
• Hybridizes with other species.
  
• Seeds spread by vehicles, soil, fodder, hay, and water.
  
• Intentionally planted and sold for gardens.
  
• Fast-growing (matures in 1 year).
  
• Produces many viable seeds (~100 per plant).
  
• Tolerates a range of soil pH (acidic to alkaline).

Low Risk Traits:

• Lacks spines, thorns, or burrs.
  
• Not parasitic, aquatic, grass, climber, or geophyte.
  
• No evidence of toxicity, allergenicity, or high shade tolerance.
  
• Not known to promote fire.