Quite a few things that would be considered too tender for a New York garden thrive against a brick wall in my school garden in Chappaqua, NY. The photos above were all taken within the last few days, and show some of these plants. In one pic, some Amaryllis belladonn hybrids and a Scilla peruviana (in bud) can be seen. Careful viewing will detect the dierama in front of the amaryllis with it upright narrow iris like foliage. The Amaryllis often get burned leaf tips when they try to make winter foliage, but new healthy growth comes out later in spring, and from the looks of it, I may get some nice flowers this summer. The hand-like divided leaves of Pelargonium luridum emerge in another pic, this really seems to be the perfect spot for it, and I look forward to the large trusses of pale pink flowers in a few weeks. Gerbera jamesonii, the true species (haven't tried the hybrids in the garden yet) is in bud in another photo, this particular plant is on its third year. I have several seedlings coming along to add nearby, as it is another one of those asteraceous plants that needs a genetically different clone to set viable seed. In the same photo shoots of a white flowered tradescantia species I got from UC Berkeley many years ago (I think Sean Hogan may have collected it in Mexico) are just emerging. The tradescantia is indestructable in that spot, and does very well all summer long. Fushia magellenica grows well as a dieback shrub, showing lots of branches right now, but it didn't like the hot summer we had last year, though it bloomed anyway and looked better when cooler fall weather returned. The melianthus I posted about earlier is coming back yet again, with more shoots than ever, so I will get to enjoy its attractive foliage and wierd dark flowers (though I am not fond of their peculiar ink like secretions if I squeeze them) come summer. Euryops tysonii benefitted no doubt from the snow cover it had this winter, although it does tend to blow away or melt earlier near the wall. It grows back swiftly from undamaged portions, though it can be bothered by spider mites in hot dry weather. I haven't got it to flower in this spot yet, though this year it seems to be growing very well and I will treat it if I see mites on it again. I did see numerous very vigorous flowering plants of it on the African Hill at the UC Berkeley Botanic Garden when I last visited during summer several years ago.
It is possible that some of these plants would manage in the open garden, perhaps with protective mulch during winter, but some of them definitely need the warmth provided by the wall to keep their roots from freezing deeply during winter. Some of the plants like the dryness of the site in summer (there is a large overhand two stories above) but most like additonal water if it gets too dry. There are quite a few other species along the same wall, and some of them (like Kniphofia northiae--which it turns out can do fine in the open garden, where I have some younger plants) get a bit too vigorous for neighbors at times.