This is a tiny, strange poem, and part of its pull is that it doesn't quite explain itself. The central image is simple: winter "had" the oak, meaning the season has taken hold of the tree, stripped it, maybe overpowered it. But the poem reaches that image through an odd comparison. Winter had the oak the way a tavern has "my money / or will," or the way a bull might have its way. In each case, something is drained or dominated.
The title, "Owned," tightens the idea. The speaker seems to feel the same kind of helplessness the oak does, giving up money, willpower, or strength to something bigger and hungrier. Judging by the comparison, the feeling is a rueful kind of surrender, maybe with a bit of dry humor in the tavern.
The mood is bleak but compact. The short lines and abrupt ending leave a cold, final silence, like the season itself closing in.