Most years, different agave varieties, and other succulent varieties, throw out their flower spikes. Usually these are neat little spikes 1/2″ to 1″ in diameter, and 3′-5′ tall. Occasionally, an agave goes bonkers.
Flower spikes in this family of plant, I learned last year, is their final hoorah before kicking the bucket. They’ll hang in there, growing bit by bit, year after year, until they sense that everything is just right. When that happens, the flower spike production begins, and occasionally – it gets breath-taking, awe-inspiring, and occasionally just downright funny.
I didn’t capture a shot of the largest one I’d seen to date (last summer? summer before last?) but it was HUGE. It was well over twenty feet tall. This year, this little cluster just brightened my day. Excuse the phone camera quality, shot at a stop light (from the passenger seat!) clutter in the frame.
I’m interested to see if they simply plant more agave (they usually do) or attempt to replace it with a quick-dying annual as other landscape crews in the city do.
plumdirt 
We had some beautiful specimens here on the south coast, and the flowers were stunning. Sadly they did exactly what you mentioned – replaced them with some rather dull municipal planting and annuals. Ho Hum!!
Thankfully around here it’s usually cheaper for the crews to replant with more agave since they only have to replace them once every few years and only water during the worst of the summer weeks.
When I see them put in begonias and other pretty, but heat intolerant, water-loving plants…I just shake my head at the waste of it. They return maybe three weeks later with pansies, and then six weeks later with something else, around and around they go…
Believe it or not, there are some really nice ones here on the island…at a Wendy’s, of all places! They have a handle on them, too…allowing the side-shoots to develop, so that when the main plant blooms and dies, the others are ready to fill-in. I’ve never seen the whole bed go at once, in the 17 years I’ve been here…