After years of waiting - seriously, it's been at least 5 years that this plant has been in the ground - I have more than just two or three flowers.
Yes, it's an exotic. I planted it before my current native fascination. Yes, it's commonly planted along the freeway soundwalls here, suggesting a plebian and not-at-all-difficult-to-grow nature. Yes, it's really taken more than 5 years to flower like this. Yes, I am still pleased.
It's some sort of trumpet vine. The actual cultivar name is lost in the mists of time.
What did I do differently in the past year that could have caused it to flower? Nothing. Perhaps you could say I was served no vine before its time.
Wikipedia has this to say about trumpet vine.
"The vigor of the trumpet vine should not be underestimated. In warm weather, it puts out huge numbers of tendrils that grab onto every available surface, and eventually expand into heavy woody stems several centimeters in diameter. It grows well on arbors, fences, telephone poles, and trees, although it may dismember them in the process. Ruthless pruning is recommended. Outside of its native range this species has the potential to be highly invasive, even as far north as New England."