Pincushion Cactus
A columnar cactus covered in reddish-brown spines with a ring of small pink flowers around the top each spring. A true desert cactus that wants a sunny sill, cactus mix and almost no water in winter.
Mammillarias are the pincushion cacti, small, round or columnar, covered in spines, and reliable flowerers on a sunny windowsill. Spinosissima is the columnar one with red-brown spines, and it wears a crown of pink flowers every spring if it gets a cool, dry winter rest.
It is not toxic, but the spines are real. Keep it where a cat cannot bat it off the sill.
Light
Full sun. A south or west window. Cacti in too little light stretch into pale, thin growth that never recovers.
Water
In summer, water thoroughly when the mix is completely dry, every twelve days or so. From November to February, almost not at all; once a month at most, or nothing. That dry, cool rest is what triggers flowering.
Soil and potting
A cactus mix with extra grit or pumice. A small terracotta pot. Repot every three years or so, with gloves and a folded newspaper to hold it.
Feeding
A half-strength cactus feed every eight weeks in spring and summer.
Propagation
Offsets around the base, twisted off and dried for a week before potting. Seed is slow.
In a hot, dry home
It is from a climate like this one. A hot west window is ideal. The one thing to give it is the winter rest: cooler and dry, which an unheated room or a spot near a window in December provides.
Pincushion Cactus varieties
Same care, different look. These are the named forms you will see for sale.
- Boobie cactus
Myrtillocactus geometrizans Fukurokuryuzinboku: a blue column with rounded bumps.
- Spiralis
Cereus forbesii Spiralis: a twisted blue-green column.
- Micodasy
Mammillaria microdasys: a small clumping pincushion.
- Fairy Castle
Acanthocereus tetragonus: a cluster of small ribbed columns.
- Old Man
Cephalocereus senilis: a column covered in long white hairs.
- Rat Tail
Aporocactus: trailing, spiny stems with pink flowers.
- Prickly Pear
Opuntia: flat, jointed pads.
- Cuddly Cactus
A spineless Cereus form.
Problems and fixes
Pale, thin new growth
Likely cause: Not enough light
Fix: Move into full sun. The stretched section stays; new growth will be normal.
Soft, brown base
Likely cause: Rot from winter watering
Fix: Stop watering. Cut above the rot and re-root the healthy top after it callouses.
No flowers
Likely cause: No cool, dry winter rest
Fix: Keep it cool and dry from November to February.
White cottony patches
Likely cause: Mealybugs
Fix: Dab with rubbing alcohol on a cotton bud.
Pincushion Cactus questions
Is a mammillaria cactus toxic to pets?
No, but the spines can injure a curious cat or dog. Keep it out of reach.
How do I get my pincushion cactus to flower?
Full sun in summer and a cool, dry rest in winter with little or no water. Flowers form in spring.
How often should I water a cactus in winter?
Almost never. Once a month at most from November to February, and only if it looks shrivelled.
Plants with a similar rhythm
Haworthia
- Light
- Medium to bright indirect
- Water
- Every 2 weeks
- Pets
- Safe
