Family: Iridaceae

Origin, Description & Uses
Dietes bicolor (African iris, butterfly flag, fortnight lily, peacock flower) is a clump-forming perennial native to eastern and southern Africa. Closely related to true irises, it has upright, sword-like evergreen leaves and pale yellow flowers marked with dark brown and orange accents. The blooms appear in succession over an extended period—often in cycles every few weeks—giving rise to the name “fortnight lily.” This species is widely planted in tropical and subtropical landscapes as a hardy ornamental for borders, mass plantings, and groundcover. It is valued for its drought tolerance, low maintenance requirements, and ability to thrive in both full sun and partial shade.

Risks & Threats
Although Dietes bicolor is not currently known to be naturalized in the Hawaiian Islands, it possesses traits that are cause for concern. It produces abundant seeds and also spreads vegetatively by underground rhizomes, enabling it to form dense clumps that may outcompete other vegetation. In climates similar to Hawaiʻi, it has shown the capacity to persist and spread beyond cultivation. These characteristics indicate a potential to escape gardens and negatively impact tropical island ecosystems, particularly in disturbed or unmanaged areas. Choosing a low-risk or native alternative is recommended to help safeguard Hawaiʻi’s unique and vulnerable plant communities.

High Risk Traits:

• Able to grow in tropical and subtropical climates
  
• Naturalized or naturalizing in Australia and New Zealand
  
• Regarded as a persistent garden and landscaping weed, and a potential environmental weed in Australia
  
• Other Dietes species are weedy and invasive
  
• May be unpalatable to deer and other browsing animals
  
• Tolerates many soil types
  
• Reproduces by seeds and vegetatively by rhizomes
  
• Reaches maturity in 2-3 years
  
• Seed dispersed by water, humans, contaminated soil and garden refuse dumping
  
• Seeds may persist for one to four years before germination
  
• Able to resprout after cutting

Low Risk Traits:

• No reports of invasiveness or naturalization in the Hawaiian Islands, despite widespread cultivation as an ornamental and landscaping plant
  
• Unarmed (no spines, thorns, or burrs)
  
• Non-toxic
  
• Fire-resistant (may reduce fire risk in fire prone areas)