Astrophytum myriostigma
Family: Cactaceae​
​Common Name: bishop's cap
Origin: Astrophytum myriostigma originates from the highlands of northern and central Mexico, in stony, calcareous, or lime soils. It is found within the states of Nuevo León, San Luis Potosí and Tamaulipas, at altitudes of 750 to 1,500 meters above sea level.
Description: The bishop’s cap is a small columnar cactus, solitary or with few basal branches. It possesses 5 ribs, which may increase in number as the cacti becomes more columnar with age, disrupting the star-like form. Small trichomes cover the silvery gray flesh, creating a velvety texture, and there are no spines. Mature plants (up to 6 years) will bloom from spring to early summer, forming aromatic yellow flowers that occasionally possess red centers. These will eventually develop into red, woolly, scaled fruits.
  • Interesting Features:
    • Although A. myriostigma only flowers for two days at a time, it can bloom in succession, readily creating new flowers. However, this species may take up to 6 years to bloom.
    • The bishop’s cap is occasionally grafted onto other cacti, but is easily able to cultivate outside of grafting.
  • Uses: Astrophytum myriostigma has been used in ceremonies by the Indigenous Tarahumara people from Chihuahua. The cacti is considered “false peyote” and often confused with the hallucinogenic Lophophora williamsii, although it is unknown if A. myriostigma possesses any hallucinogenic properties of its own.

Cultivation and Care:
  • Watering: Low
    • Provide water from March to October, irrigating sparingly when soil is dry.
    • Once temperature drops at the end of October, suspend irrigation to preserve the delicate roots.
  • Soil: Plant A. myriostigma in well-draining cactus or succulent soil.
    • Maintain a pH between 6.1 and 7.8, and supplement soil with sand, chalk, and limestone clippings for the best growth.
    • Additionally, cover the surface of the pot with sand to protect the base of the plant from moisture.
  • Lighting: Cultivate in light shade, which will encourage richer and darker coloring of the stem.
    • While A. myriostigma is sensitive to direct sunlight, it can tolerate bright light for short periods of time, and may benefit from increased sun while flowering.
  • Propagation: The bishop’s cap can be propagated from seed and scions, although the latter are very difficult to root, and are not recommended.
    • Protect seedlings from direct sun, as they are very delicate.
  • Cold Tolerance: 20°F, USDA hardiness zones 9a to 11.
  • Special Accommodations: Keep dry and well ventilated to prevent insect parasitism and rot.
    • From spring to summer, feed with a low-content nitrogen fertilizer.
    • Repotting is not required very often, but if necessary, only do so in spring.

Sources:
  1. University of Arizona Campus Arboretum
  2. Llifle Encyclopedia of Cacti
  3. Plant Care Today
  4. World of Succulents
  5. Gardeners’ World
  6. Dave’s Garden

*This accession was donated by Plant Science undergraduate student Cristian Salazar De Leon in 2019. 

Cristian's notes about the plant:
  • Grown from seed in early spring 2017 here in Tucson, AZ. 
  • Cross between two Astrophytum myrostygma nudum parents with one parent presenting very minimal trichomes.
    • This could be the reason why this donated cactus has some minor trichomes on the ribs. 
  • Has been grown outside under 30% shade cloth. Has experienced winters outside in a protected area that minimizes cold wind exposure and will not be wet for the whole winter.
  • All around cool plant that all my friends want to have after seeing a cactus with no spines and star shaped