If you were marooned on a… ahem… DESERT island and could only grow one genus of cactus… okay humor me here… don’t you think it would probably be…

Mammillaria

Mammillaria is a large genus with about 140–180 species, depending on who’s listing them. So if you’re stuck on that hypothetical desert island, you won’t be limiting your options very much.

Pilbeam (1999) recognizes 181 Mammillaria species and of these Hunt (1999) accepts 145. Any way you split this genus, it is one of the most varied in the Cactaceae, and it also has wide distribution: southward as far as Colombia and Venezuela and northward extending into the American Southwest. The greatest richness and diversity of Mammillaria varieties is in Mexico.

Mammillaria carmenae is native to Tamaulipas, Mexico.

Mammillaria carmenae, a particularly blonde and pink-flowered individual cared for and photographed by Mr Sentient Meat. Spines can vary from yellow to white. Flowers can be white, pink or pink-tinged white.

Mammillaria is a very diverse group; however none of these cacti are giant trees. They are all small-to-medium-size “globular” (roundish) cacti. Some are solitary; others grow into large clumps. They all have distinctive bumps which remind scientists of breasts enough to earn the name mammillae—thus the genus name (or as they say in the lingo, the generic epithet).

Mammillaria carmenae, same plant, different angle

The plant pictured is fully grown at around 3 inches tall and 2 inches in diameter. This species is known to grow in clusters, so it’s probably time for me to move it to a larger pot where it can spread out and grow more bodies.

Mammillaria carmenae has pale yellow to white spines, and each areole (at the tip of each mammilla) has over 100 spines, obscuring the surface of the plant almost entirely. It reminds me a bit of Mammillaria candida (profiled recently) or Mammillaria lasiacantha (in the collection but not profiled yet). Surprisingly, these similar-looking cousins are not its closest relatives.

Instead, according to molecular studies by Butterworth and Wallace (2002), Mammillaria carmenae is most closely related to M pectinifera, a bizarre subminiature which is about to bloom in my yard. I hope to profile it soon. You’d never guess these two are so closely related. M pectinifera (means “comb-bearing”) resembles a strange, round top with spine-beds (areoles) like tiny, multilegged creatures. You’ll see!

See Also

ANDERSON, E. F. 2001. The cactus family. Timber Press, Portland, Oregon, USA.

HUNT, D. 1999. CITES Cactaceae checklist. Royal Botanic Gardens, Kew, Richmond, UK.

BUTTERWORTH, C.;  WALLACE, R.  2002. “Phylogenetic studies of Mammillaria (Cactaceae)—Insights from chloroplast sequence variation and hyptothesis testing using the parametric bootstrap”. American Journal of Botany 91(7): 1086–1098. 2004.

PILBEAM, J. 1999. Mammillaria. Nuffield Press, Oxford, UK.

Also… coming soon, Mr Sentient Meat, chief plant profiler for Succulent Sunday, is very excited to be upgrading his library with the top, current, go-to reference for cactus:

HUNT, D. 2006. New cactus lexicon. dh books. Sherborne, England, UK.

[I can practically feel your excitement from here. —Mr S M]

In game of natural selection, some cactus species have adapted so successfully that their natural habitat can extend across many hundreds of miles—several USA or Mexico states. Now in darkest winter, it’s time to talk about the “Snowball Cactus” which is just such a one: Mammillaria candida (Scheidweiler 1838). The spine covering on Mammillaria candida is so dense that the cactus does appear like a big snowball or puffball. The flowers can be light pink, dark pink, white with dark midveins… or even yellow!

Its habitat stretches across several states in northeastern Mexico: Coahuila, Nuevo León, San Luis Potosí, and Tamaulipas.

Mammillaria candida grown and photographed by Sentient Meat

Unlike some puffball-like mammillaria, Mammillaria candida has spines which really mean business. I thought it looked soft and friendly so I started to repot it without gloves. I thought if I moved slowly and gently I could just turn it upside down with one hand and rest it ever-so-lightly in my other hand. Big mistake! After trying this maneuver gingerly a couple times, I gave up. I can try again in the spring. With gloves.

Mammillaria candida (syn M. ortizrubiona) ML 656 - Photo : Michel Lacoste at Mammillarias.net

M candida is sometimes separated from the rest of Mammillaria into its own genus, Mammilloydia, because its seeds are not pitted and lack the perisperm found in all other mammillaria. Recent molecular studies, however, place M. candida squarely within Mammillaria, a huge genus which includes many cacti much more distantly related than Mammillaria candida.

Mammillaria candida - Photo : Willy at Mammillarias.net

See Also

Mammillarias.net gallery of species starting with C

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, photo WindsurfGirl at Flickr

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 don’t keep its roots too wet during cold weather. 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.