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Astrophytum myriostigma var. nudum (Bishop's Cap Cactus)


Scientific Name

Astrophytum myriostigma var. nudum (Rud.Mey.) Frič

Accepted Scientific Name

Astrophytum myriostigma Lem.

Common Names

Bishop's Cap Cactus, Bishop's Cap, Bishop's Hat, Bishop's Miter Cactus, Bishop's Hood


Astrophytum myriostigma subsp. nudum, Echinocactus myriostigma var. nudus

Scientific Classification

Family: Cactaceae
Subfamily: Cactoideae
Tribe: Cacteae
Genus: Astrophytum


Astrophytum myriostigma var. nudum is a spineless, usually solitary cactus. It is very similar to Astrophytum myriostigma but lacks the white flecks on its stem, and its epidermis is smooth. The stem is spherical to shortly columnar with age, up to 3.3 feet (1 m) tall and up to 4 inches (10 cm) in diameter. The number of ribs varies from 3 to 8 (usually 5). The flowers are pale-yellow, up to 2 inches (5 cm) long, and appear in spring or early summer. It takes up to 6 years to bloom.

Astrophytum myriostigma var. nudum (Bishop's Cap)

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USDA hardiness zones 9a to 11b: from 20 °F (−6.7 °C) to 50 °F (+10 °C).

How to Grow and Care

Bishop's Cap is one of the easiest Astrophytums to grow. It is sometimes seen as a grafted plant but grows very well on its roots too. Like other star cacti, it does not ask for much water and thrives even with a very small, Spartan root zone. They demand fast drainage overall and are downright hard to kill except with excessive moisture and rich soils. Very slow growth and small size is what makes them ideal for bonsai pots and other creative containers on the porch, window sill, or balcony. This is an ideal choice for beginners due to its lack of thorns, exceptional geometry, and ease of cultivation indoors.

Bishop's Cap is cold hardy to about 20 °F (−6.7 °C). For best results, it should be given light shade, although it will tolerate full sun. During the summer, it should be given moderate water, but it should be kept dry as soon as the temperature starts dropping and keep it perfectly dry in winter at temperatures from 40 to 60 °F (5 to 15 °C). Bishop's Cap grows much faster with a low nitrogen content fertilizer in spring and summer.

Learn more at How to Grow and Care for Astrophytum.


Astrophytum myriostigma var. nudum is a form of Astrophytum myriostigma.


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