I hadn't considered it could be leaves. I thought of it as a type of plant when I first saw it, but that is mainly because it looks the same (or extremely similar) to the fungi piece which grows out of the tree stump in 3933.
Hm, I do not have the 3933 set, so I can not compare directly, although you seems to be right, that it looks quite similiar. (BTW, I think leaves are also part of a plant, so your first thought was not that wrong from my point of view
.)
Maybe this is again one of these multi-purpose parts like the eggs: in farm/city live sets the white "set of bubles" are representing eggs, and in the set with the bicycle-ice-cream-seller they are representing ice cream balls.