I'll confess, I have not patterned my muzzleloading smoothbores, but I have experimented with natural wadding. You read a lot about tow (flax or hemp fiber) being used for this purpose. I've tried it; it works. I will say that tow is also used as tinder. Much of the tow (nearly always flax fiber) offered by vendors and sutlers has been treated with a fire retardant, whether they know it or not. Obviously, this would make lousy tinder, and may be the reason some folks have difficulty getting a fire going with flint and steel. On the other hand, tow treated with a fire retardant sounds like a pretty good idea for wadding in your firelock, especially if the woods are dry where you hunt.
Dr. Levy reported an archaeological find in his post above; a musket was wadded with palmetto fiber. I had heard this before, and I have tried it (I live in Florida and palmetto is a very common plant). The fiber is much like coconut fiber, which should not be surprising. It works very well for wadding, and makes excellent tinder. I made a gadget years ago, which is basically a foot-long rod of 5/16" steel with a 2" right angle hook bent in one end and a handle of antler on the other. The hook is somewhat flattened on the end. I made it for hunting arrows lost under grass or leaves, but I was amazed at how useful it is: back-scratcher, fire-poker, lightweight "pickeroon," and also palmetto fiber gatherer. It works great. If you want to gather palmetto fiber, you need to go into a palmetto thicket. Be prepared to come face to face with ticks, scorpions, "black widders," and various species of snakes.
Spanish moss, whether green (gray and fuzzy) or dead (black and fibrous; looks like pubic hair... we're all adults here), serves well as wadding. The "black moss" is also excellent tinder.
My dad, who was from Alabama, told me hornet's nest was the preferred wadding in his area. Dad was born on a subsistence farm in 1907. Muzzleloaders were in general use in that area until well after World War I. I know wasp nest works, because I have tried it, but Dad specifically said hornet's nest. There is a difference. Wasp nest is soft and compressible, while hornet nest is tough and leathery.
I have used leather wads. I first read about this in Muzzle Blasts many years ago. A 5/8" arch punch, as used for leatherwork, cuts perfect wads for a 20 gauge muzzleloader. This is a good way to use up scraps of leather which are too small for anything else.
George Emmons was a late 19th century military officer and amateur ethnographer. He wrote monographs on the Tlingit and Tahltan people of the Pacific Northwest. He reported both of these groups used shredded bark as wadding in their trade muskets. I'm guessing this was inner bark of the cedar. Meanwhile, George Bent wrote that the Southern Cheyenne people used shredded willow bark for wadding. I have used shredded (actually pounded, with a wooden hand maul) inner bark of the local southern red cedar for wadding and for tinder. It works very well for both.
I guess all of that is more than two cents worth. Maybe worth a nickel...
Notchy Bob