Family: Polygonaceae

Origin, Description & Uses:
Persicaria capitata (pink knotweed, heartweed) is native to the Indian Subcontinent, southern China, and parts of Indo-China. It is a low-growing, mat-forming perennial plant that spreads along the ground with creeping stems that can root at the nodes. The leaves are typically small, oval to heart-shaped with distinctive markings, and it produces small pink, ball-like flower clusters that give it its common name. Because of its attractive appearance and ability to quickly cover soil, it has often been used as an ornamental groundcover in gardens and landscapes.

Risks & Threats:
This species is naturalized in Hawaiʻi on Maui and the Island of Hawaiʻi and is potentially naturalizing on Kauaʻi and Oʻahu. Persicaria capitata spreads aggressively through both creeping stems and seed production, allowing it to form dense mats that can smother low-growing native plants and reduce habitat quality. It thrives in disturbed areas, lawns, and moist environments, where it can quickly expand and outcompete desirable vegetation. Because it is already showing signs of spread and establishment in multiple parts of the Hawaiian Islands, it possesses traits that are cause for concern and could detrimentally impact tropical island ecosystems. When available, choosing a low-risk or native alternative is recommended to help protect Hawaiʻi’s unique ecosystems.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Thrives in tropical climates
  
• Widely naturalized
  
• Garden and crop weed
  
• Potential environmental weed
  
• Other Persicaria species are invasive
  
• Potentially allelopathic
  
• Alternate host of pathogens
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Forms dense mats
  
• Ligneous root
  
• Reproduces by seeds and vegetatively by rooting from nodes
  
• Can reach maturity in under 1 growing season
  
• Seeds dispersed by water, in soil and as garden waste, and intentionally by people
  
• Seeds can also be dispersed by birds
  
• Resprouts after fire and from rootstock

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Palatable to animals
  
• Ornamental
  
• Herbicides can provide effective control