Family: Urticaceae

Origin, Description & Uses
Urtica dioica (stinging nettle, common nettle, or giant nettle) is a perennial herb native to Europe, North Africa, and much of temperate Asia, extending east to Siberia and western China. It spreads by both seeds and creeping underground rhizomes, often forming dense patches in suitable habitats. The plant is well known for the tiny stinging hairs that cover its leaves and stems, which can cause a painful skin irritation when touched. Despite this defense, stinging nettle has been cultivated and used for centuries as a nutritious food, livestock forage, traditional medicine, natural fiber, and dye plant. It also has a variety of cultural and social uses and is valued in some regions for supporting beneficial insects and wildlife.

Risks & Threats
Although Urtica dioica is not currently known to be naturalized in the Hawaiian Islands, it possesses several biological traits that raise concern for tropical island ecosystems. The species spreads aggressively through extensive rhizomes and abundant seed production, allowing it to establish persistent colonies that can outcompete other vegetation. It readily colonizes disturbed areas, roadsides, streambanks, and other moist habitats, making it well adapted to expanding into suitable environments. Dense stands may displace native plants, reduce biodiversity, and create barriers to recreation and land management due to their painful stinging hairs. Because of these invasive characteristics, Urtica dioica has the potential to negatively impact Hawaiian ecosystems if introduced and allowed to spread. When selecting plants for landscaping, restoration, or agriculture, Plant Pono recommends choosing a low-risk or native alternative whenever suitable options are available.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Naturalized in mid- to high elevation areas in the tropics
  
• Widely naturalized (but no evidence from Hawaiian Islands)
  
• A disturbance adapted agricultural weed of numerous crops
  
• Other Utrica species have become invasive
  
• Stinging hair affect animals and humans
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Reported to form dense stands
  
• Reproduces by seeds in two growing seasons
  
• Spreads vegetatively by rhizomes
  
• Seeds dispersed attached to clothing, fur, or feathers, as a produce contaminant, by water, potentially by wind, and internally by animals
  
• Prolific seed production
  
• Forms a persistent seed bank (at least 5 years)
  
• Resprouts after fires (but does not withstand repeated cutting)

Low Risk Traits:

• Due to predominantly temperate range, may only become invasive at higher elevations of tropical regions
  
• Consumed by animals despite stinging hairs
  
• Dioecious
  
• Herbicides provide effective control