Yesterday I went to two garden centers in northern Virginia and came back almost empty-handed, I'm proud to say. Betty's Azalea Ranch runs wonderfully cheesy full-page color ads in the Post each week and has been around forever, but I had never been there before. It's a huge place with what looks like a pretty good selection of plants. I was concentrating on pots and hooks and they had a nice selection of each. Their pots are 30% off right now, and I was very tempted, but since I don't really have a plan yet, I held off. I'd go back.
The other place was the Fair Oaks outlet of Merrifield Garden Center, which I loved. I'd been to their original location years ago, but this one seems even better. Their selection is enormous, and it's arranged logically (think of that!) in alphabetical order by sun or shade. The staff seems very knowledgeable, too. One person suggested that climbing hydrangea (with which I seem to be obsessed) would grow too much (up to 40 feet) and develop a woody stem too big for my proposed site. She recommended abelia instead. The variety she showed me (though I did not jot down its Japanese name and have not been able to reconstruct it) has attractive, oval leaves and a pale yellow, scented spring bloom. More delicate than the hydrangea but still sturdy enough for the site. Plus, it thrives on drought. I need to do more research, since there seem to be several varieties, many of them more shrub-like than vine-like.
This person also suggested hellebores planted in front of the trellis, which appeals mightily.
Two other recommendations for shade plants I might not follow up on, but I was mildly interested: Rubus calycinoides 'Emerald Carpet' is a ground cover with a interestingly rough leaf, related to raspberries and can take sun or shade. Rohdea japonica is another shade-lover that might work under the oak tree, but somehow I'm not terribly enamored of it.
I came back with a big hanging fern and hook for the back side of the trellis, garden plans dancing in my head.
The two places make a good day trip (they're both along route 29, less than a mile apart), and I plan to go back this fall with a plant list.