Posted: 08/05/2015 at 16:27
Pyracantha is all well and good, but if the dog gets a spine in his paw or skin it will mean trips to the vet, because they always go bad. Nothing growing is going to stop a Labrador. They are bred to push their way through thick undergrowth.
Labrador and 3 ft fence is never going to be a good combination - they are active dogs. If you can't manage hedge cutters can you manage long walks twice a day?
3 ft wire or trellis on top of the original fence is a minimum I should think.