star cactus

Distribution map of star cactus

Distribution

Current

Historic

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Distribution map of star cactus (Astrophytum asterias).

Scientific Name
Astrophytum asterias
Other Scientific Names
Echinocactus asterias
Other Common Names
sea urchin cactus, sand dollar cactus, star peyote
Status
Federally and State Endangered
Global Rank
G2
State Rank
S1S2

Global Location

Star cactus occurs in the Rio Grande Valley of South Texas (Starr and Zapata counties, historically in Hidalgo, and reported from Cameron County although no habitat exists there). The cactus also grows in northern Mexico in Coahuila, Nuevo Leon, and Tamaulipas.

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Description

In the wild, star cactus is a flat, or at most, dome-shaped, spineless cactus to 15 cm in diameter. The green or dark-green to brownish green stems are divided into eight triangular sections. Each section has a row of small, white tufts of hairs down its middle. Generally, the stems are also dotted with scattered white specks. Star cactus flowers are yellow with a red to orange center (3-5 cm in diameter). The green, woolly fruits are oval (15-20 mm long, 12 mm wide) and turn brown-red at maturity.

The stems of star cactus very commonly turn color throughout the year possibly due to intense sunlight or water stress.

The stems of star cactus very commonly turn color throughout the year possibly due to intense sunlight or water stress.

Credit: Sandy Birnbaum - Texas Parks & Wildlife Dept.

The green/dark-green star cactus stems are divided into 8 sections and have scattered white specks.

The green/dark-green star cactus stems are divided into 8 sections and have scattered white specks.

Credit: Anna Strong - Texas Parks & Wildlife Dept.

The flowers of star cactus are yellow with a red to orange center and 3-5 cm across.

The flowers of star cactus are yellow with a red to orange center and 3-5 cm across.

Credit: Sandy Birnbaum - Texas Parks & Wildlife Dept.

Similar Species

Star cactus can be confused with peyote (Lophophora williamsii). The stems of peyote are bluish-green, can have 5-13 variously shaped sections, and have no white specks. Peyote also has pink flowers that are smaller (≤2 cm across) than star cactus flowers.

The bluish-green peyote stems have 5-13 sections and lack white specks. The flowers are pink and less than 2 cm across.

The bluish-green peyote stems have 5-13 sections and lack white specks. The flowers are pink and less than 2 cm across.

Credit: Anna Strong - Texas Parks & Wildlife Dept.

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Floral Characters

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Leaf Characters

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Habitat

Star cactus grows on gravelly, somewhat salty, clay or loam soils in areas of sparse vegetation in grassy thornscrub.

Habitat of star cactus

Habitat of star cactus

Credit: Paula Williamson - Texas State University

Life Cycle Events

Star cactus flowers March through May and occasionally after high rainfall; fruiting follows from April to June.

Survey Season

Star cactus can be identified all year round; however, it is most visible while in flower March to May. During extreme drought, the plants may sink below the ground surface, becoming extremely cryptic and difficult to find.

Comments

First collected from the wild in the mid-1800s, star cactus is now widely available for sale among cactus growers. In fact, it may be that over-collection in the last 150 years adds to its scarcity. However, its cryptic nature may decrease the possibility of collection. Occurring flush to the ground, star cactus can easily disappear under soil and leaf litter.