Family: Equisetaceae

Origin, Description & Uses
Equisetum hyemale is a primitive, reed-like perennial plant native to much of the Northern Hemisphere, including North America, Europe, and parts of Asia. It belongs to an ancient lineage of plants related to ferns and is easily recognized by its stiff, upright, hollow green stems marked with dark bands at the joints. The plant spreads through underground rhizomes and often forms dense, bamboo-like clumps. Historically, the silica-rich stems were used for scouring and polishing wood, metal, and cookware, which led to the common name “scouring rush.” Today, it is sometimes grown as an ornamental plant in gardens, containers, and water features because of its distinctive vertical appearance and tolerance for wet soils.

Risks & Threats
Although Equisetum hyemale is not currently known to be naturalized in the Hawaiian Islands, reports suggest it may be potentially naturalizing on Kauaʻi. This species possesses traits that are cause for concern in tropical island environments. It spreads aggressively through deep, persistent rhizomes that are difficult to remove once established, allowing it to form dense colonies that can crowd out other vegetation. It can also tolerate a range of growing conditions, particularly moist soils along waterways, wetlands, and disturbed areas. If it were to become widely established in Hawaiʻi, it could invade riparian and wetland habitats, making management challenging and potentially impacting native plant communities and ecosystem function. For these reasons, planting this species is discouraged, and gardeners are encouraged to choose low-risk or native alternatives.

High Risk Traits:

• Elevation range exceeds 1000 m
  
• Naturalized
  
• Weedy and difficult to remove
  
• A potential agricultural and environmental weed
  
• Related Equisetum species have become invasive
  
• Toxic to cattle and other grazing animals
  
• Tolerates many soil types
  
• Shade-tolerant
  
• 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:

• Thrives in temperate climates, so may only threaten higher elevation ecosystems in the tropics
  
• Unarmed (no spines, thorns, or burrs)
  
• Short-lived spores
  
• Herbicides may provide effective control