Mammillaria, a family of easy-care cactus

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Key Mammillaria facts:

Botanical name – Mammillaria spp.

Common name – Mammillaria, pillow cactus, cushion cactus, and more depending on the species
Family – Cactaceae
Type – Cactus

Height – 16 inches (40 cm)
Use – pot
Exposure – light, but without direct light
Soil – sandy, gravely, well-drained, dry

Planting – spring
Flowering – May to June

Native to Latin America and to the Southern United States, the Mammillaria genus includes 180 different species, among which you’ll find: M. candida, M. longiflora, and also M. plumosa… However, those species most commonly found in garden stores are without a doubt Mammillaria elongata and Mammillaria matudae.

These small cylindrical or spherical cacti never grow any larger than 8 inches across for 16 inches in height (20 cm wide and 40 cm tall). Their areoles are equipped with spikes which, depending on the species, are sometimes covered with woolly, silky strands. These cacti often start off as solitary growers, then bunch out as many spontaneous side shoots appear.

They flower during the day with funnel-shaped blooms set all around the top crown. Each flower ranges from 1/4th in to nearly 2 inches (7 to 40 mm), and colors range from white, yellow orange to pink and red, depending on the species. Blooming generally occurs in spring, and each flower is followed by small oval fruits that are green or red.

Planting Mammillaria

Mammillaria are frost-vulnerable cactus, so they cannot be planted outdoors unless your climate has very mild winter temperatures. The lowest they can take is 40°F (5°C). Generally, in temperate climates, it’s grown in pots, except for the following few species: M. polythele forma nuda, M. backebergiana, M. elongata, M. karwinskiana ssp. nejapensis, M. obconella, M. petterssonii and M. rhodantha, since each of these can take cold waves when they don’t last too long.

• Fill a pot with loose, airy and extremely well-draining substrate, the “3 thirds” type (1/3^rd sand, 1/3 soil mix, 1/3 garden soil).
• Protect your hands with thick gloves to keep your fingers safe from those prickly spikes.
• Plant your Mammillaria in the substrate, press it down gently.
• Settle your pillow cactus in a greenhouse or a lean-in, or also indoors in a very luminous room but not in direct sunlight.

Multiplying Mammillaria

You can propagate your Mammillaria by separating offshoots from the mother plant. It’s an operation that is more or less delicate depending on the species, since this influences how many offshoots appear, how often they do so, and whether they’re easy to reach or not.

1. Separate new offshoots from your Mammillaria preferably when you’re repotting the plant in spring.
2. Slice the offshoot off with a knife.
3. Set it down in the open, in a warm space, for a few days.
4. Transfer the cutting into a pot that’s filled with light, loose substrate.
5. Water, and then make sure the temperature hovers between 60 and 65°F (15 and 18°C)..

Growing and caring for Mammillaria

In general, Mammillarias are easy indoor plants to grow because they don’t require much care. Only water your mammillaria during the summer, once every 10 days at most, and make sure the bottom of the pot never wallows in water. In fall, water even less, and stop watering entirely during the whole winter season: this is the normal dormant season for this little cactus. Watering can resume incrementally in the following spring.

From July to September, once a month, give your mammillaria liquid cactus fertilizer. Add the fertilizer to the water used for watering. Stop adding fertilizer in winter.

In general, Mammillaria call for repotting in spring every 3 years. Simply follow the same planting steps as above.

Diseases and pests

Mammillaria cacti are resistant to most diseases, except for rot in case of too much water or moisture. On rare occasions, you might find that they’re under attack by scale insects, red spider mites or nematodes.

To learn more, read:

• How to trigger cactus blooming – technique and timing