Ents are a race of enormous, sentient trees from Middle-earth. They are all male — the Entwives disappeared many moons ago, and the Ents search for them to this day. It is unclear exactly what this says about the issue of Gender and Flowers. Despite acting rather like one, Hornbeam is not an Ent, and none are known to work for the PPC.
The Ents played an important part in the story of The Lord of the Rings when they were persuaded by Merry and Pippin to aid in the fight against Sauron.