I can't think of any reason a little canopy wouldn't work, except to block sunlight, but how much of that do you have in winter way up there? I can imagine how soggy leaves could smother some small plants, not to mention the aesthetic drawbacks. I have similar issues and I've never come up with a remedy: I have a little rock garden and some river rock-covered areas, and cleaning them of leaves in the spring is tedious, although mine are usually dry. I suppose a leaf-blower would work, but I'm not going buy one to use once or twice a year. So far, hand-picking has been my remedy.
