Uebelmannia cacti are beloved by serious collectors, especially U. pectinifera, which has black spines, a purple body, and can grow up to 12 inches tall under perfect conditions. Their beauty, however, is matched by their rarity and their difficulty. These cacti are very hard to track down and can be expensive; 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. If you do choose to try your hand at growing Uebelmannia cacti, you can tend to them year-round indoors, where they’ll grow slowly, eventually reaching up to 3 feet over time when given the proper conditions. These are such rare and difficult plants that only those with lots of practice growing cacti will likely even have access to them. They’re likely to only be found in specialty shops, and novice growers may have difficulty in getting them to thrive.
Light
Uebelmannia cacti love warm, bright light and need at least eight to 10 hours of direct sunlight every day to thrive. Consider leaving the cactus on your sunniest windowsill, or move it throughout your home over the course of the day to allow it to get the most sunlight possible.
Soil
A neutral pH soil is best for your Uebelmannia cactus, and it absolutely must be well-aerated and well-draining—your cactus should never be allowed to sit in water. Look for a soil mixture that’s been specifically formulated for cacti, or consider amending a general potting mixture with sand or grit.
Water
Water your cactus regularly during its growing season from spring to summer, allowing the soil to dry out completely between each session. Come winter, you will only need to water occasionally throughout the season, and even then do so sparingly. Once established, your cactus will be extremely drought-tolerant.
Temperature and Humidity
Uebelmannia cacti need consistently warm temperatures year-round. During their growing season, they should be kept in very hot conditions, and even in winter, they should never be allowed to dip below 60 degrees Fahrenheit. They also love humidity, so consider keeping your cactus somewhere that boasts natural moisture in the air, such as a kitchen or bathroom. If your home is dry, you can spritz the plant occasionally or buy a small space humidifier.
Fertilizer
Feed your uebelmannia cacti regularly during their growing season with a balanced fertilizer that’s been diluted to half-strength. The easiest method is to mix the food into water before tending to your cacti.
Uebelmannia Cacti Varieties
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 of the three is probably U. pectinifera, while many of the others are quite esoteric. For example U. gummifera for is so rare that it only grows in very specific types of quartzite sand in Brazil and is almost never found elsewhere.
Propagating Uebelmannia Cacti
It is quite difficult to propagate Uebelmannia. 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.
Potting and Repotting Uebelmannia Cacti
If free-standing in their pots, Uebelmannia can be repotted at the beginning of each growing season by carefully lifting the plant out as a whole and replacing it in a larger container, making sure to spread the roots out in the new soil. Make sure not to pack them in too tightly, as this can damage their root systems and make it hard for them to retain water.
Common Pests/Diseases
Like most cacti, Uebelmannia is susceptible to a variety of common diseases such as scale, mealybugs, and spider mites. If you spot signs of infestation, quarantine your infected plant immediately and treat the pests with a mild insecticide or horticultural oil. Cacti can also experience environmental ailments, including root rot, sunburn, and over-watering. Avoid these issues by maintaining strict growing conditions and keeping a close eye on the needs of your plant.
