Medium sized epilith. Stem to 15 cm long. Leaves strap-shaped, to 30 cm long, to 5 cm wide, fleshy, wrinkled, tip notched. Inflorescences to 10 cm long. Flowers 1 or 2, to 10 cm wide, white; spring to autumn. Sepals lanceolate, laterals curved. Petals ovate, shorter and wider than sepals. Labellum obovate to almost round, pointed at tip. Spur 10-11 cm long, s-shaped, slender.
A. compactum Schltr. is a compact epiphyte with strap-like leaves to 10 cm long, solitary white flowers to 5 cm wide and boat-shaped labellum with a 12-13 cm long spur.
A. didieri Finet is a compact epiphyte with strap-like leaves to 5 cm long, solitary white flowers to 8 cm wide and ovate labellum with an 8-15 cm long spur.
Source: (2005). Orchidaceae. In: . Horticultural Flora of South-eastern Australia. Volume 5. Flowering plants. Monocotyledons. The identification of garden and cultivated plants. University of New South Wales Press.