Contrary to Ferocactus, they are South American, very small, with tiny spines and they like water and some shade. As Brasil and neighbouring country dwellers they like warmth, also in winter 12-15°C would be nice. Their flowers are yellow in colour but as those plants are cleistogamic, the flower bud often do not open at all and get self-pollinated inside. That is why you first see a bud and then a fruit. No flower in between. This is also a reason for their self fertility, i.e. one plant is enough to have viable seeds. Fraileas do not live long and it is advisable to sow them every several years to keep collection complete. On the other hand you can have the whole genus on half a square meter windowsill.