Hate to say it, but to the best of my knowledge it is illegal to harvest anything you mentioned within park bounderies. The Park Service has even begun to inject dye into some plants so that if a person is found with them in their possession the dye can be used as evidence for prosecution. I think they used to allow ramps to be harvested, but a recent article in one of the park newsletters mentioned that they are no longer, due to over harvesting.
PS: Might do a search on the GSMNP website for specifics
Here is a statement included at their site related to back country camping
11. All plants, wildlife, and natural and historic features are protected by law. Do not carve, deface, or cut any trees or shrubs.
"Fly-fishing has many attributes, but none more pleasing than it's ability to liberate the young boy that still hides within me and to let that boy live again without embarrassment or regret, sorrow or anguish." Harry Middleton