Star Cactus (Astrophytum asterias)
- Other Names
- Sea Urchin Cactus, Sanddollar, Sand Dollar Cactus, Star Peyote
- Texas Status
- U.S. Status
- Endangered, Listed 10/18/1993
- This small, spineless cactus resembles a sand dollar, which is one of its common names. The disk- or dome-shaped, circular body is 2-6 inches across and 1-2 inches tall. Star cactus is dull green or brownish and often has a speckled appearance due to a covering of tiny white scales. The plant is divided into eight triangular sections, each with a central line of circular indentations filled with whitish wooly hairs. Flowers are yellow with orange centers, and 2-3 inches in diameter. The fruit is an oval, fleshy berry, up to half an inch in length. The green, pink, or grayish-red fruit is covered with dense, wooly hairs. During periods of adequate moisture, star cactus is usually a dull green color; however, during droughts, the cactus becomes brown and loses fullness so that it is flush with the ground and almost perfectly camouflaged.
- Life History
- Not much is known concerning the biology of this species. In the wild, star cactus blooms from March through May and fruits from April through June. It is likely that star cactus is pollinated by insects, but specific pollinators have not been observed. Observations in the wild suggest that star cactus requires nurse plants to become well-established. The habitat in which it is found also supports a number of other cacti species, such as Lindheimer prickly-pear, twisted-rib cactus, horsecrippler, tasajillo, nipple cactus, Runyon's coryphantha, glory of Texas, and Fitch's hedgehog cactus. Star cactus plants generally grow in semi-protected areas under brush. Since this cactus is spineless, partial shading from surrounding brush may be important in providing a favorable microclimate for growth. Successful seedlings tend to be found in close proximity to shrubs, trees, other cacti, or rocks. However, plants do occur out in more open areas.
- Star cactus grows on sparsely vegetated areas in gravelly, saline clays or loams at low elevations in the Rio Grande Plains.
- Historically, star cactus was known from Cameron, Hidalgo, and Starr Counties in south Texas, and the border states of Nuevo Leon and Tamaulipas in Mexico. Presently, this species is known from one population each in Starr County and Tamaulipas.
- This species is highly prized by cactus enthusiasts and collection of wild specimens constitutes an important threat to the species. The population that once occurred in Nuevo Leon, Mexico was likely extirpated by over-collection. Loss of habitat also threatens this species. Root-plowing and other mechanical and chemical brush control practices as well as conversion of habitat to agricultural fields and urbanization have played roles in the decline of this species. It is thought that known sites in Cameron and Hidalgo Counties have been eliminated as a result of habitat conversion. Star cactus may be cultivated from seed if given the appropriate sandy medium. Most of the plants available at accredited nurseries have been propagated from seed.
Landowners and managers can help protect the star cactus by learning to recognize it and managing the sites to maintain diverse native rangeland plant communities. Mechanical brush management, herbicide use, and seeding to non-native grasses should be carefully planned to avoid impacts to areas where this plant grows. Since this cactus is highly prized by collectors, landowners can also help by not revealing the exact location of the plants and by protecting the site from trespass. Cactus enthusiasts can help by not collecting this plant from the wild, and by patronizing only those nurseries which do not dig plants from the wild.