Mammillaria is a genus that includes several cacti that are commonly found at shows and garden centers. Common called powder puff cacti, they are popular both for their appearance and their desirable traits in cultivation. This huge genus of plants contains at least 275 species of highly variable forms, many of which are highly prized among collectors. Although this genus include some plants that are difficult to maintain, the most common ones are usually very easy to grow and are small plants with a slow growth rate, so you can grow them as houseplants for many years.
This cactus produces small, round offsets that cluster around the parent plant. The body of the plant is stocky and usually a blue/green color. The plant is covered in white, silky hairs that encase the entire plant. It looks like a powder puff, but don't touch it! The spines are sharp. It will produce small white or red flowers in summer, often in a circular or halo shape.
|Botanical Name||Mammillaria spp.|
|Common Name||Powder puff cactus, powder puff pincushion|
|Mature Size||3 to 5 inches high and 3 to 4 inches in diameter|
|Sun Exposure||Bright, even light|
|Soil Type||Rich, fast draining cactus mix|
|Soil pH||6.1 to 6.5|
|Flower Color||Red, white|
|Hardiness Zones||N/A (houseplant; but can be grown outdoors in zone 8 to 10)|
|Native Area||Southwest United States, Mexico, Caribbean|
How to Grow Powder Puff Catcus
If you can grow cacti and succulents successfully, you can likely grow the most popular varieties of Mammillaria catci without too much trouble. To encourage better flowering, allow the plants to enjoy a cooling period in the winter. This includes suspending watering and, if necessary, moving the plant to a cooler location.
Unlike many other cacti, which use their ribs as storage devices, the Mammillaria feature raised tubercles, from which spines emerge. When you water, the tubercles expand to allow for increased water storage. The flowers emerge from the axils of these tubercles on the previous year's growth, which accounts for their interesting halo effect.
It's imperative that the cactus is not exposed to prolonged dampness and sitting water. Never let your cactus sit in a dish of water. Lastly, make sure to fertilize during the growing season for the best results.
Mammillaria species appreciate strong light, but many species dislike more than four hours of direct summer sunlight. Provide bright, even light for the best results.
A rich, fast-draining cactus mix is ideal.
Allow the soil mix to become nearly dry between waterings, then water thoroughly. Immaculate drainage is essential; never let the pots sit in water. Suspend watering in the winter, but mist occasionally.
Temperature and Humidity
This cactus thrives with temperatures between 70 and 80 degrees Fahrenheit. In the winter it will become dormant. Keep it in a dry, cool area at temperatures between 60 and 65 degrees, which will encourage spring flowers. In the summer, the plant can be moved outside.
During the growing season, fertilize with a cacti fertilizer mix. Suspend feeding during the dormant winter period.
Potting and Repotting
Repot as needed, preferably during the warm season. To repot cacti, make sure the soil is dry, and gently remove the pot. Knock away the old soil from the roots, removing rotted or dead roots in the process. Treat cuts with a fungicide. Place the plant in its new pot and backfill with potting soil, spreading out the roots. Leave the plant dry for a week or so, then begin to water lightly to reduce the risk of root rot.
Propagating Powder Puff Cactus
Mammillaria cacti can be propagated easily from offsets, which readily form in clusters around the base of the mother plant. To propagate, carefully remove the offset and set it on a paper towel for a few days to allow a callus to form over the cut surface. Place the new plant in a pot with a potting soil mixture, and keep in a warm place until new roots emerge. Once the plant is established, repot it into a regular container.
Varieties of Mammillaria
There are multitudes of Mammillaria in circulation, ranging from varieties that are very easy to grow to those that are very difficult and are highly prized by collectors.
- M. zeilmanniana is by far the most popular (in fact, the most popular of all type of cactus by some measures). It has the unusual trait of blooming several times throughout the summer with multiple rings of pink and white flowers around the crown.
- M. spinosissima is another popular species and has been in cultivation for a long time. It features a ring of red flowers and, like M. zeilmanniana, is very easy to grow.