Question

Is this a complete sentence? A bushy, overgrown hedge along the fence.

Answer 1

Nope. That is considered a fragment. 
The subject is present: A bushy, overgrown hedge [located] along the fence.
This can't be complete, however, because there is no verb and such to explain much else. 

A complete sentence could be "A busy, overgrown hedge along the fence caught my attention."

*caught is a verb.