Family: Piperaceae

Origin, Description & Uses:
Piper aduncum (spiked pepper) is a fast-growing shrub or small tree native to a wide region from Mexico through tropical Central and South America. It typically thrives in disturbed areas, forest edges, and moist lowland environments. The plant is recognized by its long, narrow flower spikes and aromatic foliage, characteristic of the pepper family (Piperaceae). In its native range, it has been used in traditional medicine for a variety of purposes, including treatments for skin conditions and infections, and it is sometimes valued locally for its essential oils and potential insect-repelling properties.

Risks & Threats:
In Hawaiʻi, spiked pepper is already naturalized on Maui and is potentially naturalizing on Oʻahu, indicating it can successfully spread beyond cultivation. This species is a concern because it grows quickly, produces large numbers of seeds, and can form dense stands that crowd out native vegetation. Its ability to establish in disturbed forests and along stream corridors allows it to compete with and displace native plants, reducing habitat quality for native wildlife and altering ecosystem function. Because it possesses traits that are cause for concern and could detrimentally impact tropical island ecosystems, it is important to manage its spread carefully. When possible, choosing low-risk or native plant alternatives is strongly recommended to help protect Hawaiʻi’s unique ecosystems.

High Risk Traits:

• Naturalized beyond native range (escaped in Florida, SE Asia, Pacific Islands)
  
• Grows in disturbed areas, canopy gaps, and fallows (indicator of human intervention)
  
• Invades hardwood hammocks and agricultural fallows (considered a serious problem in some areas)
  
• Congeneric weed (Piper auritum) is aggressive and invasive
  
• Host for a pathogen (Nectria haematococca) that affects black pepper
  
• Tolerates wide range of soils (excluding salty or excessively dry)
  
• Forms dense thickets and monospecific stands
  
• Reproduces vegetatively via suckers from root crown
  
• Propagules dispersed unintentionally (via equipment) and intentionally (as ornamental)
  
• Propagules bird- and bat-dispersed; survive gut passage
  
• Persistent soil seed bank (up to 69-78% of seed bank in some sites)
  
• Tolerates mutilation (suckering, resprouting from broken roots)

Low Risk Traits:

• No spines, thorns, or burrs
  
• No evidence of allelopathy, parasitism, or toxicity to animals/humans
  
• Not a fire hazard (grows in wet habitats)
  
• Propagules not adapted to wind or water dispersal (primarily animal-dispersed)
  
• Well controlled by herbicides (e.g., 2,4-D, Garlon)