Answer: Annuals and perennials always look best if they're planted in drifts. Very narrow borders do not allow you to layer perennials in drifts from tall to medium to short, since the average plant takes up an 18" diameter space. From a design standpoint, even if you were to only layer 3 single plants in a garden bed, it would have to be 4 1/2' - 5' wide to accommodate them.
Planting naturally short plants will solve some of the space problem. Those that will look best all season include Heuchera sanguinea, Hosta lanceolata, Statice latifolia, Papaver nudicaule, Platycodon mariesi, Herbaceous spirea, Centaurea, Siberian wallflower, Coreopsis, Fringed bleedingheart, Mistflower, dwarf Daylily, Coralbell, Sea-lavender, Iceland poppy and creeping Balloonflower.
Enjoy your garden!
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