treehouse
a small house built among the branches of a tree
The children spent the summer playing in their treehouse.
treetop
the uppermost part of a tree, its canopy or crown
A bird nested high in the treetop.
treeline
the boundary beyond which trees do not grow, often on mountains
We stopped at the treeline before the alpine tundra began.
treehugger
informal term for an environmental activist or conservationist
The local treehuggers organized a protest to save the old oak.
treeless
lacking trees; barren of trees
The treeless plain stretched to the horizon.
treefrog
a small frog adapted to living mainly in trees
At night we heard the calls of treefrogs in the rainforest.
treescape
a view or arrangement of trees in a landscape
The artist painted a dramatic treescape with silhouetted pines.
tree-lined
having trees planted along both sides (of a road, avenue, or path)
They walked down a tree-lined avenue toward the town square.
apple tree
a tree that produces apples
Every autumn we pick apples from the apple tree in our yard.
treelet
a small or young tree
The gardener transplanted several treelets to the new park.