Astrophytum

The genus, Astrophytum or star cactus, is native perennial cactus of Southern Texas and Mexico and has 6 accepted species. They are found in areas that have hot, muggy summers and short, dry winters. The genus name, Astrophytum, originates from two Greek words, astron, meaning "star" and phyton meaning "plant." These cacti are very popular and have over a 100 cultivars. The species and cultivars vary in shape, form, texture, and whether they have spines or not. 

These cacti prefer full sun and well-drained, acidic, sandy soil or potting mix that is suitable for cactus and succulents. The soil needs to dry out completely between waterings. They are intolerant to standing water or soggy soils. They are drought and dry soils tolerant. As the weather turns cool, they should be kept dry. They can tolerate summer temperatures of 70 to 95 degrees Fahrenheit, and winter temperatures of 40 to 70 degrees Fahrenheit. They thrive in dry and semi-arid climates. Indoor cacti will overwinter in a cool, dry room with some sunshine. 

The different species have different characteristics. Some are short and stubby while others are columnar can reach 1 inch to 6 feet tall. Some species have green stems while others tend to be grayish. Some species have spines and others are spineless. Some have a star-shape form, dome-like, or have long narrow, cylinder-like stems. The flowers are funnel-shaped and have many petals. The flower color ranges from white to yellow with orange or red centers. The fruits are red to olive-green berries that contain many seeds.

The star cactus is considered vulnerable due to collection and loss of habitat. The species, Astrophytum asterias or sand dollar cactus, is listed as endangered by the United States Fish and Wildlife Service. However, there are many cultivars available.

One of the unique cultivars would be add interest on a window sill or sunny room. In warm, dry climates, consider a container plant on the patio or garden area. 

Insects, Diseases, and Other Plant Problems:  Monitor for mealy bugs, scale, and spider mites. Overwatering, poor drainage or soggy soils can result in root rot or fungal infections.