I've been looking at some lists of the 'nine sacred trees' of the celts, and there have been some shaky crisscrosses. In most online sources I've found there have been only eight... or nine, with two being interchangable.

Here's what I've found:

Nine sacred woods

Willow of the streams
Hazel of the rocks
Alder of the marshes
Birch of the waterfalls
Rowan of the shade
Yew of resilience
Elm of the brae
Oak of the sun
Ash of the shadows

Ash is often listed as 'Ash of the Shade', and most of the eight-tree lists I've seen have either ash or rowan, but not both. Can anyone shed some light on this?