Gymnocalycium flower bud

This is Gymnocalycium denudatum rio negro, the one remaining bud against the partially opened flowers. They opened for the first time today, and they probably came fully open, although I was outside chopping trees and didn't notice until the sun was well off them late this afternoon.

Since I last photographed the buds, all the cacti have had an outing. I discovered a fairly serious mealy bug infestation, so they were all taken outside for insecticide dipping and spraying. They came back inside yesterday, shiny and clean looking. I'm hoping I won't get too many splitting from excess water uptake.

If it's sunny tomorrow, I'll have to remember to see whether this final bud opens, and check out the other flowers.