SUCCULENT SUNDAY: Mammillaria plumosa, puffy plumed pillows

Mammillaria plumosa, fall flowers usually white or cream, here with pale pink stripe

Part of the magnetism of cacti and succulents is their strangeness—how they differ from mundane plants. Even more fascinating are the strangest-of-the-strange: cacti and succulents which have evolved bizarre features or eccentric adaptations.
     Enter Mammillaria plumosa. It's a cactus and it has spines, but these "spines" have evolved differently. They do not pierce or prickle. Instead, they sprout from each areole like tiny fountains of feathers. They certainly protect the body of the plant—but it's the soft protection of plumage rather than the hard protection of armor... or the outright weaponry of your typical cactus.
     Mammillaria plumosa forms clusters in calcareous rock clefts of Coahuila and Nuevo Leon in Northeast Mexico, home to many gorgeous and desirable cacti and succulents... such as Ariocarpus scaphirostris, subject of a previous Succulent Sunday. Like many cacti, it is protected on List II of CITES international wildlife treaty.
     Mammillaria plumosa is popular with home growers. (Yes, home growers. I hate the C word, collectors.) It is not terribly difficult to grow if you avoid keeping its roots too wet. Or at least that's what they tell me. So far, so good! Pictured is my plant blooming happily in a mix of 95% pumice, a naturally airy volcanic rock. This should help avoid the dreaded root rot. Time will tell; our first winter together is knocking at the door—this week with freakish 90 MPH winds in Los Angeles! Ah but the winds aren't as dangerous to cactus as wet combined with cold.
     Mammillaria plumosa rewards proper care by regular flowering (usually white but sometimes with a light pink midstripe), especially in autumn. And it spreads outward to form a clump. These clumps can be divided. Separated heads are reported to grow new roots with some ease. This makes it the best kind of long-term project for the home grower—your growing success is rewarded with more plants which you can give away to your friends.
     And they look good.

See also

Mammillaria plumosa article at Cactus Art
Mammillaria for sale at Miles' To Go cactus nursery
From The Cactus Family by Edward F. Anderson (2001):

Mammillaria plumosa F. A. C. Weber 1898
Feather Cactus
Chilita plumosa (F. A. C. Weber) Orcutt 1926, Ebnerella plumosa (F. A. C. Weber) Buxbaum 1951

Plants forming low, dense mounds to 40 cm (16 in) wide. Stems globose, light green 6–7 cm (2.4–2.8 in) high and in diameter. Tubercles very soft, cylindrical, without latex, axils woolly. Central spines absent. Radial spines about 40, plumose, white, 3–7 mm (to 0.3 in) long. Flowers white, to 15 mm (0.6 in) long. Fruits club shaped, deep purplish rose, to 15 mm (0.6 in) long. Seeds blackish brown to black. Distribution: Coahuila and Nuevo Leon, Mexico.