Family: Equisetaceae

Origin, Description & Uses
Equisetum ramosissimum, commonly known as branched horsetail or branched scouringrush, is an ancient, primitive plant native to parts of Europe, Asia, Africa, and Australia. It belongs to a group of plants that reproduce by spores rather than seeds and are closely related to species that existed millions of years ago. This perennial plant forms dense clumps of upright, jointed green stems that are rough to the touch due to their high silica content. The stems are often branched, giving the plant a bushier appearance than other horsetails. Branched horsetail is sometimes grown as an ornamental plant in water gardens, ponds, and moist landscape areas for its unusual, architectural look. Historically, horsetails were also used as natural scouring tools for polishing wood and metal because of their abrasive silica-rich stems.

Risks & Threats
Although Equisetum ramosissimum is currently not known to be naturalized in the Hawaiian Islands, it possesses several traits that raise concern for tropical island ecosystems. This species spreads aggressively through deep, creeping rhizomes that allow it to rapidly form dense colonies that are extremely difficult to eradicate once established. Horsetails can also reproduce by spores, further aiding their spread. In other regions where horsetails grow, they can become persistent weeds in wetlands, agricultural areas, and disturbed habitats, outcompeting other vegetation and forming thick stands that are hard to control. Because of its vigorous growth, ability to regenerate from underground rhizome fragments, and tolerance of a wide range of environmental conditions, Equisetum ramosissimum could potentially invade moist habitats and waterways in Hawaiʻi. Preventing introduction and planting of this species can help protect native plants and sensitive tropical island ecosystems from possible invasion.

High Risk Traits:

• Elevation range exceeds 1000 m
  
• Naturalized
  
• An agricultural weed
  
• Related Equisetum species have become invasive
  
• Toxic to cattle and other grazing animals
  
• Shade-tolerant
  
• Tolerates many soil types
  
• May hybridize with other Equisetum species
  
• Spread by spores and vegetatively by rhizomes
  
• Can resprout if only aboveground vegetative material is removed

Low Risk Traits:

• Unarmed (no spines, thorns, or burrs)
  
• Short-lived spores
  
• Herbicides may provide effective control