Family: Asteraceae

Origin, Description & Uses
Aztec marigold (Tagetes minuta) is an annual herb native to Brazil and southern South America. It grows rapidly to 3–7 feet (1–2 m) tall and produces finely divided, aromatic leaves and clusters of small yellow flower heads. The foliage has a strong scent due to its essential oils, and the plant has been cultivated as an ornamental, culinary herb, medicinal plant, and source of essential oil used in perfumes, flavorings, and insect-repellent products. It has also been grown as a cover crop and for its reported nematode-suppressing properties in agricultural systems.

Risks & Threats
Aztec marigold is naturalized in Hawaiʻi and possesses traits that are cause for concern. It grows quickly, produces abundant seed, and readily colonizes disturbed sites, roadsides, pastures, and open natural areas, where it can form dense stands that compete with native vegetation and other desirable plants. These characteristics could detrimentally impact tropical island ecosystems by altering plant communities and reducing biodiversity. Because this species is already naturalized in Hawaiʻi, planting and intentional spread should be avoided, particularly near natural or unmanaged areas. Where it is already widespread, management should focus on preventing further spread into new locations. Whenever possible, choose a low-risk or native alternative for landscaping and restoration projects.

High Risk Traits:

• Naturalized on Hawai'i
  
• Serious agricultural weed in 19 crops across 35 countries
  
• Forms dense stands, outcompeting native vegetation
  
• Produces >29,000 seeds per plant with up to 95% viability
  
• Dispersed by wind, animal attachment, and crop seed contamination
  
• Tolerates wide altitude, rainfall, and soil pH (4.3–7.0)
  
• Allelopathic (suppresses other plants)
  
• Benefits from fire and disturbance
  
• Widely cultivated and naturalized globally
  
• Congeneric species are invasive
  
• Annual (reproduces within one year)

Low Risk Traits:

• No spines, thorns, or burrs
  
• No known toxicity to humans or animals (used as food and medicine)
  
• No persistent seed bank (<1 year)
  
• Not shade-tolerant (requires full sun)
  
• No vegetative reproduction