Family: Tropaeolaceae

Origin, Description & Uses
Tropaeolum majus, commonly known as garden nasturtium, is a fast-growing trailing or climbing herb believed to have originated as a cultivated plant derived from wild ancestors in Peru. Valued for its brightly colored flowers and rounded, shield-shaped leaves, it is widely grown as an ornamental in gardens, hanging baskets, and landscapes. The flowers, leaves, and immature seeds are edible and have a peppery flavor, making them popular in salads, as garnishes, and in herbal remedies. In Hawaiʻi, garden nasturtium has escaped cultivation and has become naturalized on Kauaʻi, Molokaʻi, Maui, and Hawaiʻi Island, with populations also potentially naturalizing on Oʻahu. It is commonly found in mesic, disturbed habitats, particularly at mid-elevations, and has been naturalized in the islands since at least the late 1800s.

Risks & Threats
Although attractive and useful as a garden plant, garden nasturtium is naturalized in Hawaiʻi and possesses traits that are cause for concern. Its vigorous growth, abundant seed production, and ability to spread beyond cultivation allow it to establish in disturbed habitats, where it can form dense patches that compete with native vegetation and alter plant communities. These characteristics could detrimentally impact tropical island ecosystems if the species continues to expand into new areas. Because Tropaeolum majus is already widespread in parts of Hawaiʻi, efforts should focus on managing existing populations and preventing its use and spread into areas where it is not yet widely established to minimize further negative impacts. Whenever possible, choose low-risk or native ornamental alternatives that provide similar aesthetic value without the risk of escaping cultivation.

High Risk Traits:

• Naturalized in Hawaiian Islands and several other locations
  
• Thrives in higher elevation tropical climates
  
• Controlled in Hawaii and other locations because of threats to natural environment
  
• Other Tropaeolum also have become invasive
  
• Shade-tolerant
  
• Tolerates many soil conditions (and potentially able to exploit many different habitat types)
  
• Smothering habit
  
• Reaches maturity in under 1 year
  
• Spread by garden waste, water dispersed seeds, gravity and intentionally be people
  
• Will resprout from cut stems

Low Risk Traits:

• Edible leaves, flower buds and seeds
  
• Non-toxic
  
• Landscaping and ornamental value
  
• May be effectively controlled with herbicides