Well, that's my problem. I don't know yet for sure what the plant looks like. But I definitely have found things growing that look like the Tribulus terrestris in my rose bed. I yanked them out thinking it was the shrubs out front being fruitful and multiplying and I don't like them either! I'm going to put a few seeds in a pot and see what comes up. Stay tuned.
Thanks for those links, Lin! And if these turn out to be those, I'll have an entry for the database!