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Eulychnia castanea spiralis, or Unicorn Horn Cactus, photographed at Tula Plants & Design. Eulychnia castanea spiralis, or Unicorn Horn Cactus, photographed at Tula Plants & Design.

Eulychnia castanea spiralis

Botanical Name —  Eulychnia castanea spiralis

Common Name —  Unicorn Cactus, Unicorn Horn Cactus

Plant Family — Cactaceae


Background


Taking on many forms and shapes, the odd Eulychnia castanea spiralis is a nursery cultivar highly sought by cactus collectors around the globe. They can take heaped and bumpy ‘monstrose’ forms, columnar hooped ‘discoidal’ forms, columnar twisting ‘spiralis’ forms, or – the holy grail for collectors – ‘cristata,’ or crested forms. This one takes on an architectural fan-like structure and has elements of all the other forms. All Eulychnia castanea spiralis in existence are a growing variant of the same nursery cultivated clone.


Take One Home

 

Growth Requirements


Sun

  • These cacti prefer lots of sun, at least five hours of direct sun daily. Young plants may need shade protection from afternoon sun.
  • Indoors, a south facing window is ideal. Outdoors, seat them in a place where they will get plenty of sun exposure, but protect them from intense, peak afternoon sun.

Temperature/ Humidity 

  • These plants are semi-hardy. They prefer a warm climate where temperatures remain between 60 and 80 °F.  Best to bring indoors when the temperature falls below 50 °F.  
  • The crested form is more frost sensitive and should never be left out in freezing conditions.

Water

  • Eulychnia castanea spiralis prefers to stay on the dry side. In the summer, water them only when the soil has dried out entirely. Always err on the side of underwatering. They are built to withstand drought, and overwatering is one of the quickest ways to kill them.
  • During the winter, water very infrequently if at all. Water should be restricted to only enough to keep the stems and branches from shrivelling.

Soil/Roots

  • They prefer a gritty, sharply draining mix. A cactus mix would work fine. You can amend it with sand or fine pumice up to 50% to improve grittiness and drainage. 


Flowering

  • These plants rarely flower, but in the optimal summer conditions, small cream colored flowers can appear across the top of the cacti’s body.

Fertilization

  • You can fertilize during the spring and summer months to give them a boost or refresh their soil. Apply a balanced cactus fertilizer diluted at half strength, once a month.
  • A once-a-year, springtime repotting (not necessarily into a bigger pot) could refresh the soil as well. 

Propagation

  • Propagation can be done by cuttings in summer.  Let cutting callus before planting.  Make sure that it is kept warm and dry to root.

Health


Diseases

  • Eulychnia castanea spiralis are not especially susceptible to pests or diseases. Keep an eye out for common pests such as aphids, mealy bugs, and scale. 
  • Root rot can be a common issue if overwatered. 

Maintenance (pruning, legginess, repotting)

  • These plants are very low maintenance. They prefer to be rootbound. Repot them once every one to two years. Early spring is the best time to repot, when they are just waking from their dormancy. 

Toxicity

  • Eulychnia castanea spiralis are not known to be toxic to humans or pets.