This herb was one of the many herbs and wildflowers I encountered on my Lammas walk up to the Ridgeway yesterday. My two adult companions, Rose and Steve (we also had a little berry of a child with us) had much knowledge which they were happy to share, and thanks to Steve for identifying mugwort.
Mugwort has been used for magical purposes in times gone by, and probably still is. The generic name comes from Artemis, the Greek form of Diana, goddess of the moon. Medicinally the herb has been associated with child-birth and mixed with chamomile and agrimony was used to alleviate cramp. Before hops, mugwort was used in brewing to make beer more intoxicating. It can also be used to enhance dreams.
Mugwort is associated quartz crystal, silver, pearls and moonstone. It is deeply connected with Midsummer's Eve - as if used as a bathing herb prior to the shortest night offers many blessings. Bunches of dried mugwort from the previous year's harvest may be tossed into the Midsummer fire.
In Holland and Germany one of it's many names is St John's plant because of the belief that if gathered on St. John's Eve (Midsummer's Eve) it will protect against diseases and misfortune.
ref: Herbal Magick by Paul Beyerl and The Illustrated Plant Lore by Josephine Addison