As another poster said, in years past the Wonders of Life pavilion had some great informational displays on the topic. There were also live gardeners available for questions.
I'm not quite sure if this is what you mean, but some of the items displayed at the festival are very old Bonsai trees. Some have been in training for many decades. Let's say many are older than Epcot itself.
I can also add, WDW has had topiaries since at least the early 70's. There used to be many of them growing under the path of the MK monorail.
We've also witnessed the overnight transformation of Epcot, and talked to CM's about it. Some plants are out before the start of the festival. Some festival items are in the park, but covered. Many arrive overnight. Plantings are ripped out and replaced overnight.