I'm guessing that some of the herbals you take aren't ~causing~ the thornys, but causing them to exit. But the reaction at your Gram's place is interesting... I wonder what a soil test would show?
Could you tell if the seeds/pods/thorns were connected to each other before they came out? By "threads" or filaments? Maybe connected in a shape of the U.S.? Here's a thought provoking link to an article about a slime mold that connected into the shape of the Tokyo rail system:
http://www.wired.com/wiredscience/2010/01/slime-mold-grows-network-just-like-...
And here's a picture of a pumpkin from a couple years ago that I thought looked a lot like the U.S.! It wasn't mushy or anything, but green around the image of North America, under the skin of it.
