Family: Pteridaceae

Adiantum hispidulum, commonly called rosy maidenhair fern or rough maidenhair, is a fern native to Australia, New Zealand, Asia, and parts of Africa. It is easily recognized by its triangular, rough-textured leaflets that emerge with a rosy-pink or bronze tint before maturing to deep green. The fern thrives in shaded, moist habitats such as forest understories and rocky crevices, and its graceful fronds have made it a popular choice in landscaping and as a houseplant.

In Hawaiʻi, A. hispidulum has naturalized on all the main islands, spreading from plantings into shaded forests and disturbed areas. It reproduces readily by spores and has the potential to outcompete native ferns and other understory species. Because it is hardy, adaptable, and capable of establishing in the wild, it should be planted with caution and monitored closely. Choosing non-invasive alternatives is a better way to enjoy the beauty of ferns while helping protect Hawaiʻi’s native ecosystems.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Grows in tropical to subtropical climates
  
• Widely naturalized in main Hawaiian islands
  
• Environmental weed (threatens native biodiversity and endangered plant species)
  
• Other Adiantum species are invasive
  
• Probably unpalatable
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Forms dense clumps or mats capable of excluding other vegetation
  
• Reproduces by spores and vegetatively by rhizomes
  
• Apogamous (able to reproduce asexually without fertilization)
  
• Spores dispersed by wind, probably by water, and possibly through external attachment to shoes or equipment in soil
  
• Planted intentionally by people (source of future propagules)
  
• Prolific spore production
  
• Spores can remain viable for 10-15 years
  
• May recover after fire

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• No verified reports of toxicity
  
• Ornamental