Mammillaria backebergiana ernestii aka Pincushion Cactus

Mammillaria backebergiana subsp. ernestii is an easy-to-care-for cactus with few demands, making it excellent for beginners. It tolerates some neglect and requires minimal attention beyond proper light and occasional watering. The main keys to success are providing well-draining soil, avoiding overwatering, and ensuring adequate sunlight.

This small columnar cactus grows up to 30 centimeters (12 inches) tall with a slender diameter of 5-6 centimeters (2-2.5 inches). The stems start globose (ball-shaped) and become cylindrical with age. Due to their slender form, taller stems may grow crooked or lean without support. The plant readily offsets to form clumps over time, creating attractive multi-headed specimens.

This cactus thrives in warm conditions with daytime temperatures of 70-75°F (21-24°C) and cooler nights around 60-65°F (15-18°C). It is frost-resistant to approximately -5°C (23°F) when kept completely dry, making it hardy in USDA zones 9b-11b. During winter dormancy, cooler temperatures are acceptable and can even promote better flowering the following season.

Yes, this cactus produces beautiful bell-shaped flowers in late spring to early summer. The blooms are purplish-red to pink-lavender in color, measuring 18-20 millimeters long. Flowers emerge in rings around the woolly crown of the plant, creating a striking display against the spiny green body. After flowering, dull green fruits develop and ripen to purplish-red, containing brown seeds.

This cactus can be propagated from offsets (pups) or seeds. For seed propagation, stratify seeds by refrigerating in a moist substrate for 4-6 weeks, then sow on the surface of cactus mix without burying (seeds need light to germinate). Keep warm and lightly moist until germination occurs.

Repot every 2-3 years in spring, or when the plant has outgrown its container. Choose a pot only slightly larger than the current one, as Mammillaria prefer being somewhat root-bound. Use containers with drainage holes and terracotta pots are ideal as they allow soil to dry efficiently. Refresh the well-draining cactus mix when repotting, and allow the roots to dry for a day or two before watering.

The most common pests are mealybugs, root mealybugs, spider mites, and scale insects. Mealybugs appear as white cottony masses and can be treated with rubbing alcohol on a cotton swab. Spider mites cause silvery damage and fine webbing, thriving in dry conditions. Root rot from overwatering is the most serious disease threat, caused by fungi like Phytophthora and Pythium. Prevent problems by providing good drainage, avoiding overwatering, and inspecting plants regularly.

Yes, this cactus can grow outdoors year-round in USDA zones 9b-11b where temperatures stay above 25°F (-3.9°C). It is frost-resistant to approximately -5°C when kept dry. In cooler climates, grow it outdoors during warm months and bring inside for winter. Choose a location with full sun and excellent drainage. The plant naturally grows on steep cliffs in Mexico at elevations of 1,400-1,900 meters.

This subspecies is endemic to the State of México in central Mexico, with the type locality near Tonatico. It grows on steep, often inaccessible cliffs at elevations of 1,400-1,900 meters in desert and dry shrubland habitats. The plant clings to rocky cliff faces alongside other succulents including Agave brevifolia and Selaginella lepidophylla. Due to its remote, difficult-to-access habitat, wild populations are not well studied.

Mammillaria backebergiana has two recognized subspecies. The nominate form (subsp. backebergiana) has a mid-green body and 1-3 central spines, found across Guerrero, Michoacán, and México State. The subspecies ernestii (this plant) is distinguished by its darker green body, typically a single central spine that is darker in color, and a more restricted range limited to México State near Tonatico.

Pincushion Cactus does best in dry soil and should only be watered sparingly.

The Pincushion Cactus is very susceptible to soil that is too wet, so it's essential to choose a potting soil that drains well and does not retain excessive moisture. A soil mix that includes plenty of perlite or vermiculite for drainage and some organic matter for nutrition is ideal. You can easily create this type of soil by adding a few handfuls of perlite to regular cactus soil from the store.

Pincushion Cactus thrives in bright and direct sunlight. To ensure your plant receives enough light to survive, place it less than one foot from a window. The current weather in your area may affect the placement in your home. For example, if you live in a region that has longer and more intense periods of sunlight, then you may want to place the plant farther away from the window to avoid direct sunlight and reduce the risk of sunburn. Alternatively, if you live in a region with relatively milder temperatures and less intense sunlight, then you may be able to place the plant closer to the window for increased exposure. Ultimately, the current weather in your area should be taken into consideration when determining the best placement for your Powderpuff Cactus.

Pincushion Cactus prefers dry environments, but by misting the plant or providing extra humidity, water will linger on the leaves and create an ideal environment for fungi that could be harmful.

The Pincushion Cactus is known for its slow growth and doesn't require fertilizing beyond its potting soil. Replacing the soil in its pot once a year should offer it sufficient nutrition. It's essential to remember that plants get their energy from the sun, not from fertilizers.

No verified data on the toxicity of this plant exists within Ploi's records. Should you, someone in your family, or your pet ingest plant material with an unknown toxicity level, it is recommended to seek medical advice.

During the wintertime, it is common for Pincushion Cactus plants to go dormant and their growth rate may slow down. Therefore, the amount of waterings should be spaced out more.