Mammillaria plumosa is a clumping plants that forms low, dense mounds sometime up to 40 cm wide entirely covered by the mass of white feathery spines.
It has 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 are small, flattened, 2-4 mm long, somewhat woolly in their axil. 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.
Flowers are whitish yellow, up to 3-15 mm long (occasionally with pink midstrips), with a strong sweet scent.
Mammillaria species like most cacti they're drought tolerant and need very little care and attention to grow well . Plenty of sunshine will keep this cacti more than happy. Provide bright, even light to encourage tight growth and flowering. Some shade during a hot summers day can be helpful to prevent sunburn.
Allow the soil mix to become nearly dry between watering, but then water thoroughly. Suspend watering in the winter, but mist occasionally. Not enough sunlight and over-watering are common mistakes.
Use pot with good drainage and a very porous potting media.
Feed every 4 weeks with a high potassium fertiliser during summer
Suited for window sill and dish gardens
For watering cacti, the golden rule is to make sure the soil is completely dry before watering! This will stop the roots from rotting. It is advised to always use a pot with a drainage hole so that excess water can get drained out. If kept in a sunny area, you will need to water it once every week. If it is in a semi shaded or filtered light area, you might need to water it once in 2 weeks.
Cacti like soil that is well aerated and fast draining. You can fertilise the cactus in the summer months when it is in its growing season. During the winters it is best to cut back on any fertiliser and let the plant rest.