having a line of trees: a treelined road.

Is tree lined hyphenated?

If there is no possibility of ambiguity when using a compound word, then a hyphen is probably unnecessary. For example, “I walked along a tree-lined street.” The hyphenated word is perfectly fine, but is there any doubt about the meaning if I wrote; I walked along a tree lined street?

What is tree lined?

: having trees on both sides a tree-lined street.