I'm not really a gardener, but our borders (about 2-3 foot wide) are decidedly bare. I don't want to have to frost-protect anything, I just want plants that fill space, look nice, and aren't laden with poisonous berries or spikes. I'm thinking smallish things for the front and some medium-ish things to go behind them and conceal the fence a bit? Where do I start? We're on a clay soil, I think, garden is half shade and half sun. Thanks in advance...