sadly, slugs like lots of young fresh plants, so you need to protect them for a few weeks anyway!.........trailing geranium are pretty, as are things like, trailing ivy, used as a filler with your other plants, I grow clematis in pots too, I have early flowering ones, and Summer flowerings ones too!......they are really pretty, and good value, as they come back year after year, as long as you re pot them, and cut them back in Autumn...............hope this gives you some ideas!.......