Open plan garden ideas required

I would be grateful to hear ideas about separating my front garden from my neighbours as they don't bother with theirs anymore. I divided it up with just a foot gap and planted lots of bulbs and flowers, but it doesn't do the job really. It needs more height up to about 3 ft. It is 26 ft long by about 16 wide, I have a paved drive at the side of it and wanted to avoid it looking like a huge car park.