The last flower on a potted Ferocactus wislizenii is coming to the end of its life cycle, having lasted weeks longer than earlier ones. Blooming late has some advantages, because the lower temperatures do not dry out the flowers as quickly. However, a flower this late is unusual. Normally, the flowers have gone to fruit by mid-September, but this year, many weird things happened in my garden. Getting late flowers is one of the better happenings, so no complaint here!
The yellowing fruit on the cactus will eventually dry to a scaley brown, and then crumble and blow away. Barrel cactus fruits are not edible as with some other cacti, not because they are poisonous, but because they are small and don’t have a lot of flesh. As they mature, they are somewhat juicy, but not enough to spend time harvesting.
In the past, Native Americans boiled and ate the flowers, or made a tea with them. Other than that, there wasn't much use for the flowers or fruit in their culture. Nowadays, some people like to dry the flowers when they are at their best, and use them in oils and soaps. They have no fragrance, so I guess it’s for looks. I think the flowers look better left on the cactus where they will eventually form fruit. By fall, the dried yellow and brown fruit is in keeping with the season.