Description: Small usually
globose depressed, up to 13cm
greyish-brown to blue-green (rather variable in colour in
and in some specimens it is almost blue-black). The 9 to 10
ribs are divided by deep grooves into
Areoles : deep-set
5 to 7 thin radial spines
that are straight or curved toward the stem,
short, curved, pale brown or grey, tinged with red at the base.
on the crown,
measuring 3 to
4 cm in length and the same across, open wide in sunlight,
and commonly of a most rich purple-red colour, sometimes
pinkish-purple (but also white, pink or orange).
stamens are purple, the
anthers and the 6
stigma whitish yellow. This plant blooms in early summer
when it is only 2.5 cm.
It is fast growing and can bloom one year after being sown.
ovary is green, long and
dehisces (splits) down its length.
The synonym name Gymnocalycium venturianum is very
common in collections,
and even at cactus nurseries. It is a very variable species in
its general appearance.
There are also
many hybrids with a wide range of flower colours.