Rare and Unusual Cacti Worth Growing

Once you have the common varieties figured out, the cactus world opens up into something genuinely surprising. There are thousands of species, and many of the most interesting ones are not hard to find at a good garden center or online retailer. Here are some varieties worth seeking out.

Moon Cactus (Gymnocalycium mihanovichii mutant)

The moon cactus is one of the most striking plants in any cactus collection. The brightly colored ball on top is a mutant cactus that lacks chlorophyll entirely, which is why it comes in vivid shades of red, orange, yellow, and pink. Because it cannot photosynthesize, it is grafted onto a green rootstock that provides the energy it needs to survive. They are widely available and stay small. The colorful top portion does not live indefinitely, but the rootstock can be regrafted when needed.

Fairy Castle Cactus (Acanthocereus tetragonus)

The fairy castle cactus grows as a cluster of upright columns that branch at different heights, creating a skyline that resembles the turrets of a castle. It grows slowly and stays manageable indoors, rarely exceeding a foot or two in height for many years. It tolerates a range of indoor conditions and is one of the more forgiving columnar cacti for beginners.

Old Man Cactus (Cephalocereus senilis)

The old man cactus is covered in long, shaggy white hair that gives it an immediately recognizable appearance. The white fibers are actually modified spines that protect the plant from sun and temperature extremes. It grows slowly as a tall column and is a conversation piece in any collection. It needs bright direct sun and excellent drainage.

Brain Cactus (Mammillaria elongata cristata)

The brain cactus is a crested form of the ladyfinger cactus, where a genetic mutation causes the growing tip to develop in a fan or wave shape rather than a single point. The result is a plant that looks remarkably like a brain or coral. Each one is slightly different because the crested growth is unpredictable. It stays compact and is well-suited for a windowsill.

Totem Pole Cactus (Pachycereus schottii monstrose)

The totem pole cactus is another monstrose form, this time with a smooth, bumpy surface that lacks the usual ribs and spines of a normal cactus. Its irregular, lumpy texture gives it a sculptural quality unlike most other cacti. It grows as a single upright column and can eventually reach several feet tall indoors under good light conditions.

Star Cactus (Astrophytum asterias)

The star cactus, also called the sand dollar cactus, is a small, flat, spineless cactus with eight symmetrical ribs dotted with white flecks. It stays very small, rarely exceeding a few inches in diameter, and produces yellow flowers with an orange center. It is a bit more demanding than some others, preferring a very gritty soil mix and careful watering, but it is one of the most elegant cacti you can grow.