'Rowan tree and red thread - have witches all in dread'
On May eve Rowan crosses used to be worn in UK and were sometimes fastened to cattle (or their barns) for protection against witches and other 'evil doers'. Legend has it that crosses had to be made without a metal knife to work properly. Rowan branches were also bought indoors on a Good Friday as this tree had a reputation for strong protection against psychic forces.
This 'mish-mash' of folklore and Christianity indicates older uses of tree having been 'assimilated' into a religion that converted people by adapting their beliefs and practices to its own ends. 'Rowan' is most interesting of tree names with connections to both ancient Norse and Hindu/Sanskrit culture. Spelled several ways it is connected to old Norse word 'Runa' - meaning a charm - and being able to ward off effects of 'evil eye'. In even earlier times 'Runa' was Sanskrit word for 'magician'. 'Run-stafas' were staves cut from Rowan tree and inscribed with runes for magical (and most likely protective) reasons. The smooth bark is ideal for this purpose.
The Rowan was such a sacred tree to Celts that many churchyards in Wales still include tree, not unlike Yew tree in English churchyards. The berries were much used by Celts for brewing wine, spirit, flavouring mead, ale, perry and cider. Try squeezing some of fresh berry juice and putting it into a gin and tonic - it makes a convincing alternative to Angostura bitters. The fresh juice is mildly laxative and good for soothing inflamed mucous membranes. In herbal medicine juice forms basis of an astringent gargle for sore throats and in 19th century it was used to treat scurvy - disease of vitamin C deficiency.