Astrophytum are compact perennial cacti with ribbed, spherical or columnar stems bearing woolly, sometimes also shortly spiny areoles, and large, solitary, funnel-shaped flowers in summer, followed by red or green berries
A. myriostigma is a cactus forming a spherical or shortly columnar, ribbed grey-green spineless plant to 20cm tall; light yellow flowers 5cm across, sometimes reddish in centre, open in summer