Can't answer your ? BJ but have to say Wow

That's pretty, isn't that a stigma [shiny green structure] in the middle though? or is it vestigial?
I wasn't aware that they were dioecious.

I used to have photos of globosa as I had a couple in the previous garden. They will be in a shoe box somewhere, I will have a look for you.

Yes, the stigma is most probably vestigial and structural. But the female flowers don't usually have visible stamens, which are very withered. It's never been documented in this species but a few other apparently dioecious Buddlejas from the Americas can have very occasional hermaphrodites (trioecious).

Ah they are cryptically dioecious. that explains it.

if hermaphrodite aren't they just a monoecious example? seems odd to give another name for what is a common flower arrangement.

Trioecious means a species with male, female and hermaphrodite individuals.
Monoecious usually means separate male and female flowers on the same individual, although it is often confusingly used for plants with hermaphrodite flowers.
Indeed B.globosa is cryptically dioecious, so cryptic it is hard to believe they aren't hermaphrodites.

I've not long planted one in the garden, a while away from flowering I think, or it was last time I checked. I'll be happy to take a shot for you as and when though.
I planted it to hide neighbour weeds until my replacement hedge grows.

I'm familiar with the mono/di terms but tri makes sense ie 3 forms on one plant. nothing like mother nature for complexities.