Rainbow Pincushion

I bought my first one (grown locally) in 2006. It was only today that I confirmed its botanical name thanks to the photos on PlantFiles....Read More It is now 6" tall and 3.5" wide, which doesn't sound very impressive, but it is. The longest spines are a little over an inch long. It has withstood our very taxing winter conditions, while occasionally being brought into the garage for short stretches during frosts.
From experience, I can fully agree with palmbob's statement "Very easy cactus to grow with a lot of cold hardiness and ability to tolerate excessive watering."
The spines are a terrific golden yellow, and they are even pettable, if you pet down at just the right angle. It flowers like crazy, though it would take a very enterprising insect to go down into those spines to pollinate them.
I really can't recommend this plant highly enough; it should be a mandatory inhabitant of every cactus pot worldwide.

I should add that mine is a single trunk which shows no signs of pupping. Does this mean it was seed-grown? Or am I thinking of the fact that seed-grown aloes tend to be more prone to single trunking than their pup-derived counterparts?

Update, Sept. 2011: I just bought a baby one grown locally, and a large one grown by Costa.

commonly available species, much more so than the regular red-spined M rhodanthas. Flowers much of the year. Very easy cactus to grow w...Read Moreith a lot of cold hardiness and ability to tolerate excessive watering. Mine are bit prone to mealy bug, but otherwise one of the easiest cacti I grow outdoors in southern California

A beautiful little Mamm, with nice golden spines. Young spines are very sharp and pointy. Older spines appear to lose their tips and curv...Read Moree heavily.

According to the New Cactus Lexicon, this plant is M. pringlei.

The subspecies 'aureiceps' has flowers that range from dark pink to red. It has roughly 25 gold-yellow radial spines and 4-7 central spin...Read Morees per areole.
The subspecies 'pringlei' has deep magenta flowers. It has 18-22 yellow radial spines and 4-7 golden yellow central spines, slighly curved inward and longer than the other subspecies.
The subspecies 'rhodantha' has 17-24 almost translucent clear white radial spines and 4-7 reddish to red-brown central spines curved inward slightly which are longer than the other subspecies. The flowers are a deep purple-pink.
The subspecies 'fera-rubra' has 15-18 white radial spines and reddish brown central spines that are shorter than the 'rhodantha' subspecies. Flowers range from dark pink to red and are smaller.
The subspecies 'mccartenii' has 13-15 radial spines and 4-5 reddish brown central spines that are shorter than the 'rhodantha' subspecies.
The subspecies 'mollendorffiana' has 24-28 radial spines and 4-7 central shorter brownish-red central spines. Flowers range from dark pink to red and are also smaller than the other subspecies.