Heather in Celtic Lore
Heather (Ur) was associated with romance, dreams and feelings for the Celts. Perhaps, it's use in making mead (a pretty strong alcoholic drink) helped in making this association. Brides in the highlands still wear heather blooms. The plant was also used to make brooms and intestinal medicine. Thus, it had an association with cleaning as well.
The Ogham symbol for Heather (Ur) translates as a "U" in English.