Family: Fabaceae

A creeping, prostrate, woody herb that is invasive on all the main Hawaiian Islands. Native Central and South America, Mimosa pudica, commonly called sensitive plant or sleeping grass, is a nuisance in most tropical places. Likely introduced accidentally to Hawaii well before 1860, the sensitive plant was documented as naturalized in 1864. It was recorded as a widely spread invasive plant just seven years later.

This plant is troublesome throughout the tropics, harming agriculture and degrading pasture land. This creeping herb is wind, bee, and self-pollinated. Reaching reproductive maturity in less than a year, one plant is capable of making 600 to 700 seeds annually. Seeds remain viable yet dormant in the soil for 44 years. They spread extremely long distances through external attachment on animals, birds, humans, and as a contaminant on other objects. Water dispersed seeds as well, especially floodwaters.

Capable of growing under wedelia and other thick brush, this invasive species is shade tolerant, also a fire hazard when dense thickets are dry. Sensitive plant is a severe nuisance in lawns, making barefooted fun in Hawai’i difficult. They are naturalized on all the main Hawaiian Islands, growing particularly well in lower elevations. This self-compatible plant can genuinely make a dense population with just one seed.

The genus name Mimosa comes from the Greek word mimos, meaning to mimic, a reference to the movement of leaves in the genus. The species name pudica, in Greek, means bashful, a reference to the sensitive leaves that fold when touched.

Description and Dispersal:

• Prickly stems are red in color
  
• Twice compound leaves are comprised of 26 pair of leaflets which close up at the midvein when touched
  
• Pink spherical flowers, in groups of 1 to 5, are born from the leaf axil.
  
• Growing in clusters, seed pods follow after flowering.
  
• Brown pods densely covered in bristles (a means for external attachment) with pickers along the margin split open to reveal numerous seeds
  
• Seeds are spread externally attached on animals, birds, and humans
  
• Seeds are spread by water
  
• Small seeds are spread on contaminated tools, machinery, tires, etc

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Thrives in tropical climates
  
• Naturalized in the Hawaiian Islands and elsewhere
  
• Weed of lawns and landscaping
  
• Agricultural weed of several crops
  
• Possible environmental weed
  
• Other Mimosa species are invasive
  
• Sparsely to densely prickly
  
• Potentially allelopathic
  
• Contains mimosine, which may be toxic to livestock
  
• Alternate host of nematodes
  
• Tolerates many soil types
  
• May form dense cover
  
• Reproduces by seeds
  
• Able to reach maturity in <1 year
  
• Seeds dispersed externally on clothing and fur, as a contaminant in soil and sand, and also by water
  
• Seeds survive gut passage if consumed by animals
  
• Prolific seed production
  
• Seeds viable for years, with potential to form a persistent seed bank

Low Risk Traits:

• Provides fodder for livestock (palatable despite reports of toxicity)
  
• Ornamental, medicinal and novelty uses