"Remedies are prescribed according to the individual and the cause and nature of the anxiety and identifying the exact feeling underlying the problem. Agrimony and aspen are useful for mild to moderate anxiety. For severe cases, use cherry plum or red chestnut. Anxiety for no apparent reason can be treated with aspen. Anxiety over the welfare of loved ones (such as worrying excessively about the well-being of others) can be treated with red chestnut; anxiety about inability to cope could be helped by taking elm or larch.": http://www.npadnews.com/alternatives.asp
I know people who suffer from Panic and / or Anxiety Disorder and I just recovered notes (I made a few years ago) re-inspired me to search: aspen+anxiety which gave the above site as the first search result. This site looks like it can be a helpful resource for virtually anyone who suffers form panic and / or anxiety disorder, for whatever reason.