Family: Fabaceae

Origin, Description & Uses
Native to a broad region stretching from Europe and North Africa through Asia to Myanmar and parts of eastern and southern Africa, Melilotus albus (white sweet clover, honey clover) is a fast-growing biennial herb in the pea family. It produces tall stems with clusters of small white flowers that are highly attractive to bees and other pollinators, making it a valued honey plant and forage species. White sweet clover has also been used for soil improvement, erosion control, green manure, and livestock fodder because of its ability to fix nitrogen in the soil. In Hawai‘i, it is naturalized on Kuaihelani (Midway Atoll), Moloka‘i, Maui, and Hawai‘i Island.

Risks & Threats
Although sometimes planted for agricultural benefits, white sweet clover possesses traits that are cause for concern in tropical island ecosystems. This species produces abundant seeds, can spread rapidly in disturbed areas, and is capable of forming dense stands that compete with native vegetation and alter natural plant communities. Its ability to enrich soils with nitrogen may also change nutrient conditions in sensitive habitats, potentially favoring additional invasive species. Because Melilotus albus is already naturalized in Hawai‘i and has invasive tendencies elsewhere, it could detrimentally impact tropical island ecosystems if left unmanaged. Choosing low-risk or native alternatives is recommended when suitable.

High Risk Traits:

• Broad climate suitability
  
• Grows in temperate to tropical climates
  
• Naturalized on Hawaii, Maui, Molokai and Midway Island; widely naturalized elsewhere
  
• Agricultural weed
  
• Environmental weed
  
• Other Melilotus species are invasive weeds
  
• Allelopathic
  
• Can be toxic to animals
  
• Host of 28 viral plant diseases
  
• Tolerates many soil types
  
• Forms dense patches that can exclude other vegetation
  
• Reproduces by seed
  
• Self-fertile
  
• Can reach maturity in <1 year (but often >1 growing season)
  
• Seeds dispersed by water, internally by animals, as a contaminant of other crops and seed mixes and intentionally by people
  
• Prolific seed production
  
• Forms a persistent seed bank
  
• May tolerate fire and cutting at certain growth stages

Low Risk Traits:

• Unarmed (no spines, thorns, or burrs)
  
• Provides fodder for livestock (palatable despite reports of toxicity)
  
• N-fixing (improves soil fertility)
  
• Not reported to spread vegetatively
  
• Beneficial to bees and other pollinators