Party!! Yes, make a big batch of chili and we will all be over to help you eat it. It may take a while for everyone to arrive as people in three countries were involved in this solving this mystery.
I think that sooby/Sue and JRsbugs/Janet Super Sleuth are some pretty good botanical experts.
With all the folks adding their suggestions and helping to eliminate plants it all works to get us to the one correct answer. I really hope your horses will make a full recovery. Maybe when they are looking more fit you could take some photos and post them?
