Description: Clumping plants form low, dense mounds sometime up to 40 cm wide entirely covered by the mass of white feathery spines.
Stems: Depressed globose or somewhat elongate, without latex, spherical, 4- 7 cm high and in diameter. Light green, but appearing white because of the dense spines.
Tubercles: Small, flattened, 2-4 mm long, somewhat woolly in their axil.
Radial spines: About 40 per areole 1 - 7 mm long, white, weak, interlacing, feathery. The spines in this specie have very long hairs along the spine-axis arranged as are the segments of a bird's feather and that furnish an epidermal protection against the blasting sun of the desert.
Central spines: Absent.
Flowers: Whitish yellow, up to 3-15 mm long (occasionally with pink midstrips), with a strong sweet scent. Perianth segment with a reddish line running down to the centre.
Fruit:
Seeds: Black.
Mammillaria plumosa Feather Cactus
Cultivation: Needs regular water in summer, but for best appearance keep water off of the spines. Do not let the soil become too dry in winter, either. It does better with a good drained soil mix since it is a rot prone species,whose roots are easily lost in pots that stay damp for any length of time. It takes a couple of years to offset, but once it starts it can fill a 25cm pot in just a few years. Propagation: Seeds, offsets (Cuttings root quickly). Needsfull sun or light shade in sum and blooms are whitish yellow and up to 15 mm long (occasionally with pink midstrips), with astrong sweet scent.