The genus Astrophytum contains six species of North American cacti that can be found in Mexico and the southwest of the United States. Three of the six species are widespread domestic cultivars known as “star cactus,” so-called because of their ribbed shape that resembles a star. The body of a star cactus is covered in areoles that have sharp golden or black spines. Only a few types are capable of producing white flocking (an adaptation designed to protect the plant’s tissues from sunlight), as well as yellow, orange, pink, or red blooms that open from the core of the plant.
The star cactus, sometimes known as a “living rock,” is known for its extremely slow growth and enormous size when mature. Rare valuable species like Astrophytum asterias are extremely difficult to grow and typically require grafting onto an Echinopsis cactus for the best results. The star cactus is among the most attractive cacti in North America, but it does require patience to develop properly.
Care Guide
Light
Outdoors, place star cacti where they will get at least six hours of daily direct sunlight. Put potted indoor cacti on a bright south or west-facing ledge to provide them with the minimum four hours of direct sunshine they require.
Soil
Like the majority of cacti, this species needs sandy, permeable soil that drains well. For indoor specimens, potting soils with perlite, gravel, and pebbles, as well as organic material to retain some moisture, are the best. Due to its original habitat’s lack of dense plants and grasses, star cacti thrive in xeriscaped landscapes or in rock gardens outdoors. Acidic soil with a pH between 5 and 6.5 is preferred for star cacti. The plant could die under alkaline soil conditions.
Water
Despite having a reputation as a desert plant, many cacti, including star cactus, benefit from the “soak and dry” method of cultivation. It’s better to thoroughly soak the plant before letting it dry completely in between watering. During the growing season, Astrophytum in pots and outdoors should both receive a deep water soak once a month, making sure drainage is complete to prevent the roots from sitting in water. Avoid watering your outdoor cactus at all during times of rain and in the winter.
Humidity and Temperature
Despite having a reputation as a desert plant, many cacti, including star cactus, benefit from the “soak and dry” method of cultivation. The plant should ideally receive a thorough soaking before being completely allowed to dry out in between watering. During the growing season, Astrophytum in pots and outdoors should both receive a deep water soak once a month, making sure drainage is complete to prevent the roots from sitting in water. Avoid watering your outdoor cactus at all during times of rain and in the winter.
Fertilizer
The majority of cacti thrive in poor soil, but during their growing season (June through September), indoor star cacti can benefit from light fertilization. Monthly feedings using balanced houseplant fertilizers (one with a 20-20-20 ratio) diluted to half strength may boost the vigour of your plant. Avoid fertilizing your cactus in the late autumn as it prepares for hibernation, and don’t fertilize it at all over the winter.
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