We put in three glass rings, two with Agave Americana or Century Plant from my home garden and one with a baby Queen Victoria. Both features in the Yucca/Agave/Succulent/Cacti/Sotol section of the new Guide...which should be out in February '09.
Tom's another regular, he's a fellow brewer and devoted gardener!
When I asked Zilker to remove some of the trees in the area (I later found out had been poisoned by an attempt to control root growth on other nearby trees) I was told that this area was once an Indian Burial ground. I would love to know if this is true...I haven't found any hard evidence but in respect to lore, we used all of the rocks (and there were many) to make 3 large mounds...which I think is one of the more interesting features in the new space.
Agave Victoria Reginae in glass mulch.
That's little Firecracker Fern around the Spanish Dagger.