This is a truly unusual genus of cacti. Composing only three species, Uebelmannia was only brought into the mainstream trade from South America in the mid-sixties and at the time was unlike any cactus ever seen. They are unique in appearance and can be truly impressive: Uebelmannias have vertical, distinct ribs covered in areoles in white, black, or gold. They are usually cylindrical, and their skin has an odd, waxy look to it. Together, the effect is truly one-of-a-kind among cacti.
Uebelmannias are beloved by serious cactus collectors, especially U. pectinifera, which has black spines, a purple body, and can grow up to twelve inches tall under perfect conditions. Their beauty, however, is matched by their rarity and their difficulty. These cacti are very difficult to track down and can be expensive, and in cultivation, they have specific and difficult requirements that can make them a real challenge to grow.
For that reason, these cacti are best left to experienced growers—these are not a good option for beginners. Nonetheless, their idiosyncratic shape and variety of colors make them among the most beautiful of South American cacti, and when grown to full maturity they can be great specimens.
- Light: They grow in high, bright light and need hours of direct sunlight every day to thrive.
- Water: Water regularly during the growing season from spring to summer, then water only lightly and occasionally in the winter.
- Temperature: Uebelmannias need warm temperatures. In the growing season, they should be kept in very hot conditions, and even in winter, they should never dip below 60 degrees F.
- Soil: A low-pH soil is best, and it absolutely must be well-aerated and drain well. Consider adding sand or grit to a potting mix for best results.
- Fertilizer: Feed regularly during the growing season with a balanced fertilizer like a 20-20-20 mixed into their water and diluted to half-strength.
It is quite difficult to propagate Uebelmannias. Though they can grow from seed, in common practice they are most often grafted onto another plant to help them survive. Some variants, like U. pectinifera, need to be grown from seed to grow well. They are finicky in early life; generally, propagating these cacti from scratch should be left to the experts.
If free-standing in their pots, Uebelmannias can be repotted at the beginning of each growing season by lifting the plant out (carefully) as a whole and replacing in a larger container, making sure to spread the roots out in the new soil. Don’t pack them in too tightly, as this can damage their root systems and make it hard to retain water.
The three species in this genus are U. pectinifera, U. gummifera, and U. buiningii, although there are hybrids that exist and other closely related cacti as well. The most popular are probably pectinifera. Some are quite esoteric: U. gummifera, for instance, is so rare that it only grows in very specific types of quartzite sand in Brazil and is almost never found elsewhere.
Even for cacti, these plants have a low tolerance for cold temperatures and letting them into even temperate conditions is an easy way to damage them. Make sure to keep well-watered, as well, and give them lots of light. Their roots need some space and really good drainage and keep an eye out for common pests that can damage them. Uebelmannias, however, are such rare and difficult plants that only those with lots of practice growing cacti will likely even have access to them. These will likely only be found in specialty shops, and their cultivation should be left to the experts—if you do cultivate one, though, they are among the most singular-looking of all cacti.