Chamomile(Matricaria chamomila) is rich in calcium and magnesium, making it a natural nervince, useful for calming nerves and upset stomachs and promoting sleep. Avoid if you're allergic to ragweed.
Kava(Piper methysticum) can relieve anxiety and agitation, according to Germany's Commission E. Kava's muscle-relaxing effects also make it good for alleviating tension headaches. Avoid if you're pregnant, nursing or taking sedatives.
Lemon Balm(Melissa officinalis) acts as a gentle natural tranquilizer. Combine with chamomile tea or tinctures to relieve nervousness and enhance sleep.
Motherwort(Leonorus cardiaca) is a sedative, nervine and antispasmotic, which is useful for nervousness and hysteria. A strong uterine stimulant, it should be avoided during preganancy.
Passionflower(Passiflora incarnata) is used to reduce anxiety, calm nervous stomachs and treat insomnia. May exaggerate the effects of sedative medications.
Sources: The Herbs of Life: Health & Healing Using Western & Chinese Medicine (The Crossing Press) by Lesley Tierra, LAc; Natural Health Bible (Prima) by Steven Bratman, MD, and David Kroll, PhD