Charles Ellicott Commentary Psalms 80:9

"Thou preparedst [room] before it, And it took deep root, and filled the land." — Psalms 80:9 (ASV)

Thou preparedst room. —The reference is, of course, to the casting out of the heathen in Psalms 80:8.

Didst cause ... —Rather, it struck its roots deep; literally, rooted its roots.