Mammillaria is a cotton ball-looking ornamental cactus with little but extremely sharp white spines. It grows at a very slow pace. Thanks to its beautiful funnel-shaped flowers that range from white to yellow, pink to red, this plant is often used as an ornamental feature in gardens. It can store water for drought survival.
I. Appearance and Characteristics
Mammillaria is one of the largest genera in the cactus family (Cactaceae), with currently 200 known species and varieties recognized. Most of the mammillaria are native to Mexico, but some come from the southwest United States, the Caribbean, Colombia, Venezuela, Guatemala and Honduras. The common name “pincushion cactus” refers to this and the closely related genus Escobaria.
The first species was described by Carl Linnaeus as Cactus mammillaris in 1753, deriving its name from Latin mammilla, “nipple”, referring to the tubercles that are among the distinctive features of the genus. Numerous species are commonly known as globe cactus, nipple cactus, birthday cake cactus, fishhook cactus or pincushion cactus though such terms may also be used for related taxa, particularly Escobaria.
The distinctive feature of the genus is the possession of an areole split into two clearly separated parts, one occurring at the apex of the tubercle, the other at its base. The apex part is spine bearing, and the base part is always spineless, but usually bears some bristles or wool. The base part of the areola bears the flowers and fruits, and is a branching point. The apex part of the areole does not carry flowers, but in certain conditions can function as a branching point as well.
The plants are usually small, globose to elongated, the stems from 1 to 20 centimeters (1⁄2 to 7+3⁄4 inches) in diameter and from 1 to 40 cm (1⁄2 to 15+3⁄4 in) tall, clearly tuberculate, solitary to clumping forming mounds of up to 100 heads and with radial symmetry. Tubercles can be conical, cylindrical, pyramidal or round. The roots are fibrous, fleshy or tuberous. The flowers are funnel-shaped and range from 7 to 40 millimeters (1⁄4 to 1+1⁄2 in) and more in length and in diameter, from white and greenish to yellow, pink and red in color, often with a darker mid-stripe; the reddish hues are due to betalain pigments as usual for Caryophyllales.
The fruit is berry-like, club-shaped or elongated, usually red but sometimes white, magenta, yellow or green. Some species have the fruit embedded into the plant body. The seeds are black or brown, ranging from 1 to 3 mm (1⁄16 to 1⁄8 in) in size.
| Common name | Pincushion Cactus |
| Botanical name | Mammillaria |
| Family | Cactaceae |
| Origin | Central and southwestern U.S.A., South America, Caribbean |
| Life cycle | Perennial |
| Plant type | Houseplant |
| Sunlight | Full Sun |
| Maintenance | Low |
| Soil condition | Loam |
| Drainage | Well-Drained |
| Spacing | Less than 12 in. |
| Flower color | Gold, Yellow |
| Stem color | Green |
| Flower benefit | Showy |
| Uses | Container |
II. How to Grow and Care
Sunlight
Mammillarias appreciate intense light, but many species dislike direct summer sun for too long. Plant them in an area of your garden that receives 4 hours of direct sunlight daily. If you are growing your Mammillarias indoors, place them near the brightest window in your home or office to ensure they get enough light. Place the pots on the balcony or in the garden for extra light from spring to fall if possible. Increase sun exposure gradually to prevent sunburn.
Temperature
Mammillarias are heat tolerant, but they are not cold-hardy plants. They thrive with temperatures between 70 and 80 °F (21 and 27 °C). In the winter, when Mammillarias go dormant, they like cooler temperatures between 45 and 55 °F (7 and 13 °C). These cacti can survive short exposures to several degrees below freezing but do not grow Mammillarias in the ground if they are subject to harsh weather conditions. If you live in a region that experiences temperatures colder than 30 °F (-1.1 °C), it is best to grow these cacti in pots that can be brought indoors.
Watering
Mammillaria is a drought-tolerant plant that does not require frequent watering. Water thoroughly when the soil is completely dry. When potted, water slowly, wait for water to flow out the bottom, and then pour the excess water from the tray to avoid water accumulation.
Spring, summer, and fall are its growing seasons. Water once or twice a week to keep the soil slightly wet. In winter, water less; just keep the soil from drying excessively; usually once a week. Besides, water with rainwater or distilled water rather than tap water.
Tap water contains a lot of calcium, magnesium, and other mineral salts. Long-term use tends to cause soil compaction. Avoid splashing water on its stem when watering to prevent rotting.
Soil
Mammillarias require a soil mix that provides root aeration and good drainage, whether grown outdoors or indoors. Use commercial cactus potting mixes or create your own potting mix with 70 to 80 % mineral grit, such as coarse sand, pumice, or perlite.
Fertilizing
In growing seasons (namely spring, summer and fall), fertilize mammillaria once a month with liquid fertilizer. No fertilizer is required in winter. A small amount of slow-release fertilizer can be well mixed into the soil when repotting in spring or fall.
Use nitrogen fertilizer during seedling and phosphate-potassium fertilizer before and after blooming. The fertilizer concentration should be as low as possible. It would be better to apply low-concentrate fertilizer several times rather than to use a high concentration. If the base is yellow and grows slowly, the cause may be excessive fertilizer, and fertilization should be immediately stopped.
Planting Instructions
Sow, plant, or repot in spring or fall when the temperature is 15 to 20 ℃ . Keep air humidity high when seeding. Use plastic film to cover the soil and remove it after the seeds germinate.
Use permeable clay flower pots for potted plants. Too large a flowerpot accumulates water easily, while too small a flowerpot limits the development of roots. Before planting, expose soil to blazing sunlight and disinfect to kill pathogens.
If planted in the garden, mammillaria prefers an area with full sun and loose soil. Remove all weeds and replace the soil if needed to ensure good water permeability and avoid root rot. Wear gloves or use tongs when planting to prevent your fingers from getting pricked. You can also wrap the plant in a towel to help you move it.
Pruning
Mammillaria does not require much pruning. Remove withered flowers and branches so the plant uses nutrients on healthy growth.
Propagation
There are two easy ways to propagate Mammillarias: by seeds or by dividing offsets.
Offsets
The offsets readily form in clusters around the base of the mother plant. Carefully remove the offsets using tongs, a sharp, sterile knife, or a razor blade. Allow the cut to callous over several days before placing the offset in a pot with well-draining soil. The best time to remove offsets is in spring and summer.
Seeds
Growing Mammillarias from seeds is an exciting way of increasing a collection. Sow the seeds in a pot with a well-drained soil mix in late spring or summer. Place the pot in a sunny spot and keep the soil moist until the seeds germinate. At temperatures between 70 and 80 °F (21 and 27 °C), germination usually takes a week or two. The following spring, seedlings will be ready to transplant into their own pots.
Pests and Diseases
Mammillarias are relatively disease-resistant but susceptible to pests such as mealybugs and scales.
Pests
Mealybugs and scales both damage Mammillarias by sucking plant juices. They are very difficult to see among the spines of the plants. These little guys have a waxy, white, cotton-like appearance. The root mealybugs are even harder to notice. They are found below the soil surface like white deposits on the roots. Scales are also difficult to detect.
These pests spread quickly from plant to plant. One way to control them is by using cotton swabs dipped in alcohol. Spraying the plant with 70% rubbing alcohol may help control the pests that are not easily visible.
Diseases
Most problems associated with Mammillarias grown as houseplants are bacterial or fungal diseases caused by overwatering. Removal of the affected parts of the plant is the only way to control the spread of infection. Once a Mammillaria has collapsed, it is too late for treatment.
Repotting
Repot every two or three years into a slightly larger pot. Make sure the soil is dry before repotting. The best time to repot a Mammillaria is late winter or early spring, but the repotting process can be done almost any time of the year. Do not water for a week or so after repotting to reduce the risk of root rot.
III. Uses and Benefits
There are so many different types of Mammillaria cactus that, no matter what your setting or purpose, you can surely find a variety to suit your needs.
Some species are quite delicate and suited to a sheltered indoor setting. Some are rugged, low growing, and fast-spreading and make marvelous additions to rock gardens and other challenging settings.
Still, others grow quite tall and exhibit isolated growth patterns, making them ideal as specimen plants in a cactus garden or centrally located planter.
A mini cactus garden is a good way to display several different varieties of Mammillaria indoors!
IV. Harvesting and Storage
Most fruits of mammillaria are edible. Pick the fruit when they turn red. Avoid food safety issues by confirming the species with experts. Wear gloves or use scissors and other tools to harvest.
Find Where to Buy the Best Pincushion Cactus (Mammillaria)
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