SafePlants

Rayless Arnica (Arnica discoidea)

Arnica discoidea, commonly known as rayless arnica, is a North American species belonging to the sunflower family (Asteraceae).

Taxonomy and Nomenclature

• Scientific Name: Arnica discoidea Benth.
• Family: Asteraceae (Sunflower family)
• Synonyms:
  • Arnica discoidea var. eradiata (A. Gray) Cronquist
  • Arnica discoidea var. alata
  • Arnica grayi
  • Arnica parviflora
  • Arnica parviflora ssp. alata
  • Arnica alata Rydberg
  • A. cordifolia Hooker var. eradiata A. Gray
• Related Names:
  • Arnica diversifolia Greene (pro sp.) amplexicaulis or mollis
  • Arnica x diversifolia Greene (pro sp.) amplexicaulis or mollis cordifolia or latifolia
  • Arnica ovata

Distribution and Habitat

• Arnica discoidea is native to the western United States, including California and Montana.
• It thrives in woodlands, forests, and chaparral environments.
• It generally grows at medium-to-high montane elevations.

Morphological Characteristics

• Arnica discoidea is a perennial herb, growing to approximately 0.3 meters (1 foot) in height.
• Its common name, "rayless arnica," comes from the absence of ray (ligulate) flowers in its flower heads.

Ecological Role

• The flowers of Arnica discoidea are hermaphrodite, containing both male and female reproductive organs.
• It is pollinated by Apomictic.

Distinguishing Characteristics

• Arnica discoidea can be distinguished from the similar Arnica parryi by its broader leaves and the non-nodding flower heads in bud.

Further Information

• Oregon Flora Project: http://nathistoc.bio.uci.edu/plants/index.htm# Dicots
• Discover Life: Discover Life's page about the biology, natural history, ecology, identification and distribution of Arnica discoidea
• USDA Distributional map for Arnica x diversifolia Greene (pro sp.)