Shrub to 2 m tall, sometimes scrambling. Ribs 10-13. Areoles mostly less than 1 cm apart, central spines 5-6 becoming white, radial spines about 20. Flowers with perianth segments spreading at the tip, brilliant pink. Fruit pinkish.
A. penicillata (Gürke) Britton & Rose from E Brazil is occasionally grown and differs from the above species most clearly in having narrower stems mostly less than 1.5 cm wide.
Source: (1997). Cactaceae. In: . Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.