Mythology
Peith, or guelder-rose contains the important
winter feast of Samhain - traditionally Nov 1 - now called All Saints, with Hallowen preceding it. Samhain began the Celtic year, although, perhaps confusingly, not the calendrical year (which begins with Beithe/birch).
In Ukraine, guelder rose symbolises both fighting spirit as well as the more traditional symbol of beauty.
Girls
'like Guelder Roses' appear in Ukranian songs, while in Siberia, guelder rose
berries were sometimes fermented and distilled into an alcoholic drink.
Another tree-letter, ngetal, or reed (the ng pronounced as in the french sang for blood), can appear in place of guelder rose, but became largely obsolete at some stage BC.