for me, Valerian root didn't do anything except give me horrifyingly real dreams.. I would wake up and be shocked and scared out of my mind by the reality of it. I guess you could say my anxiety went down because I was still scarred by the dreams throughout the day to care lol.
I have heard about hops and passionflower but have not tried either one... St John's Wort keeps coming up in threads too, but I haven't tried that, I find the feedback on it to vary a lot, I've heard it doesn't do anything from some people.
I've tried rhodiola rosea.. it didn't do much for me but I think after a month of taking it I did see minor improvement. It was good for a lot of other things too, energy, less of depression, it did lessen my anxiety but it worked so slowly that it's hard to see. Many health benefits seeing it's an adaptogen
For short term kava kava works really well when necessary, there aren't any negative health effects. I take it when it's absolutely necessary, around 20 minutes before I have to do whatever it is I know I won't do otherwise (sometimes just going to school). I don't know if you've tried it, it makes you unbelievably calm, I always keep some just in case.
Edit: I don't believe you can find a permanent natural 'cure'... It's all mental, eventually we just have to face our fears, it's the only way out, but for temporary situations natural remedies can be helpful.