Let this be the start of the official 'All things Mammillaria Chat!!!' thread.
I love these plants and have had great success growing some while at the same also suffered through horrible failures especially when trying non native species (which ends up being most) in the actual ground. Regular Phoenix area river flood plain soil is apparently not suited to growing most Mamillarias.
I have had great success with M. grahamii in the ground, but then that is a native AZ plant. Best growing has been in pots and hanging baskets on the east and north sides of the places I have lived where the amount of sun exposure and water drainage are pretty well controlled.
Here is picture of what came to me as M. spinossisima 'Un Pico' in flower, but this particular head is not very 'Un Pico'-ish spine-wise:
It may be an image I posted before in another thread, if so my apologies!
