From Tolkien Gateway

Ent-houses were the homes of the Ents, which seem to have been as varied in nature as the Ents themselves. Some were relatively large and complex, while others were quite basic in nature. One thing that all Ent-houses had in common was a source of fresh water, from which the Ents made the Ent-draughts that were their only sustenance.

Treebeard maintained several Ent-houses in Fangorn Forest, with the one at Wellinghall including a tree-lined courtyard, furnishings of different kinds, and a rocky bay with a curtain of falling water.

Other Ent-houses were rather less ornate: that of Quickbeam, for example, consisted of nothing more than a flat stone surrounded by rowan-trees.[1]