Mammillaria care: watering, light and repotting
Also called pincushion cactus, globe cactus · Mammillaria · Cactaceae family
60 d in winter
How often to water the mammillaria?
Allow about 14 days between waterings in spring and summer, and 60 days in autumn and winter, when growth slows down. These rhythms apply to a room with its favourite light: in a darker room the plant drinks less; in a brighter one, it drinks more.
A cool (50–59 °F, 10–15 °C), dry winter is the secret to its crown of spring flowers.
What light does it need?
The mammillaria loves the sun: a south- or west-facing window suits it, ideally less than 3 ft (1 m) from the glass. Without enough light, the stems stretch and growth slows down.
Repotting and fertiliser
Repot every 3 years, ideally in April, into a pot only slightly bigger than the last one. As for fertiliser, from May to July, feeding every 45 days is enough; the rest of the year, let it rest.
Adult size: 2–8 in (5–20 cm).
Safe for cats and dogs, according to the ASPCA.
Common problems
Won't flower
Cause: Winter too warm or too wet. What to do: Keep it cool and dry from November to February.
Brown, soft base
Cause: Too much water. What to do: Stop watering and repot into dry compost.
Frequently asked questions
How often should you water the mammillaria?
About every 2 weeks in spring and summer, and every 2 months in autumn and winter, in a room with its favourite light. The darker the room, the longer you wait between waterings. Before watering, check that the top inch of soil has dried.
Where should you put the mammillaria?
The mammillaria loves the sun: a south- or west-facing window suits it, ideally less than 3 ft (1 m) from the glass. Without enough light, the stems stretch and growth slows down.
Should you mist the mammillaria?
There's no need: indoor air suits it. Wetting its leaves for no reason can even encourage disease.
When should you repot the mammillaria?
Every 3 years, ideally in April, or sooner if roots come out of the drainage hole. Choose a pot only slightly bigger, 1 to 1.5 in (2 to 4 cm) wider, always with a hole in the bottom.
Cats, dogs, children: is the mammillaria safe?
The mammillaria is listed as non-toxic to cats and dogs by the ASPCA. A pet that eats a lot of it may still vomit, so it's best not to let it nibble.
Is it an easy plant to care for?
Yes: the mammillaria forgives a missed watering and adapts well to the home. A good plant to start with.
These are guidelines for an indoor plant in a temperate climate. Trust the soil too: a finger pushed an inch into it will tell you whether it's thirsty.