I'm probably over-agonizing about this, but I want to plant a new border garden this spring and am having trouble figuring out what to plant. The site is sunny in the winter, and pretty shady in the summer with maybe a few hours of afternoon sun. The area is about 20' long in front of a picket fence (see photo).

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In one corner at the moment a rhododendron ('Scintillation') is happily residing; I thought I might put a hydrangea ('Generale Vicomtesse de Vibraye'?) in the other corner by the gate, but I'm stumped about what to do in the middle. At one point I thought I might just have several types of hydrageas, but now I wonder if I should mix it up a bit (winter interest? Would a red-twig dogwood do here?). I do have a couple of rhodos that need to be moved ('Choinoides') but I'm not sure if this is the spot for them. Any advice for this new gardener would be great!