Commonly known as Star plants because of their appearance from above.
There are around 5 species that, apart from one, are all similar in form.
There are some subspecies and many cultivars.

Features (excluding A. caput-medusae).
Usually solitary, they are cylindrical or spherical with well defined ribs.
Areoles, on the edges of the ribs, have short pale hairs and in 2 species there are also spines.
The sides of the dark green ribs have multiple small areas of white hairs or scales.
The extent and pattern of the scales varies between and within the species.

The funnel-shaped, self sterile flowers at the top of the plant open during the day.
Flowers are up to 6 cm across and large in relation to the plant.
The long tube is very hairy and the yellow tepal lobes may have a red or orange base.
The scaly, spherical pods opening in various ways, have large seeds.
An example of these is A. ornatum.

Astrophytum ornatum.
This is done separately.

Astrophytum caput-medusae.
This species is very different from those above.
It is a flattened, sprawling plant only a few cms high.
The actual stem is very short and has long cylindrical ‘arms’ growing from it.
These are elongated tubercles up to 19 cm long.
They are dark green but almost completely covered in whitish scales.
The funnel-shaped flowers, opening in the day, are near the ends of the tubercles.
The yellow tepal lobes have orange bases.