I just read in the latest Consumer Reports "we haven't tested a commercial deer or squirrel repellant that works well"
I live in deer country. I have no idea why they don't eat mine to the ground. Rabbits get a lot of my foliage each spring, but they quickly regrow.
Curt Hanson has a tall, solar powered multi strand electric fence around his daylilies. Still, once in a while they manage to get in. Another daylily gardener I know uses a plastic green mesh fencing that they staple to their trees - I think it must be 7 or 8 feet tall. It works well as long as it does not get any rips in it. If there is the smallest opening, they will find it.