Family: Brassicaceae

Origin, Description & Uses
Nasturtium microphyllum (onerow yellowcress) is a perennial aquatic or semi-aquatic herb native to parts of Europe, western Asia to the western Himalayas, North Africa, Ethiopia, the southwestern Arabian Peninsula, and Australia. It is commonly found growing along streams, wetlands, irrigation ditches, and other moist habitats. The plant has creeping or spreading stems, small compound leaves, and clusters of small yellow flowers. In some regions it has been used as a peppery edible green similar to watercress, and it may occasionally be planted or spread unintentionally through water movement and contaminated soil or equipment.

Risks & Threats
This species is naturalized on Kaua‘i, O‘ahu, Moloka‘i, Maui, and Hawai‘i Island. Nasturtium microphyllum possesses traits that are cause for concern, including rapid spread in wet environments, the ability to reproduce vegetatively from fragments, and the formation of dense patches that can outcompete other vegetation. These characteristics may allow it to alter wetland and stream ecosystems, reduce habitat quality for native species, and interfere with water flow in sensitive tropical island environments. Because it is already established in Hawai‘i and could continue spreading in disturbed or aquatic habitats, choosing a low risk or native alternative is recommended whenever suitable alternatives are available.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Grows in warm temperate and tropical climates
  
• Widely introduced and naturalized (including Kauai, Oahu, Molokai, Maui and Hawaii islands)
  
• Possible aquatic environmental weed
  
• Other Nasturtium species have become invasive
  
• Pathogen host
  
• May be contaminated with parasites that can infect people
  
• Reproduces by seeds
  
• Hybridizes with N. officinale
  
• Self-compatible
  
• Reproduces by vegetative fragments
  
• Readily dispersed. Seeds and vegetative fragments dispersed in water, in mud stuck to birds, other animals, vehicles, equipment

Low Risk Traits:

• No spines, thorns or burrs
  
• Palatable to livestock
  
• Non-toxic
  
• Edible uses (although may be contaminated with parasites)
  
• Shade-intolerant