The cones of the Alder tree, a mystical tree that was sacred to the Celts because of its ability to live in two places at once and yet no land at all; land, water and the sodden marshes and bogs.
The Alder is a Fae tree, a tree with pale wood yet it seeps red sap; believed to be the blood of the indwelling Fae spirit of the tree. Alder groves have long been places of sacredness and fear; sacred because of the spirits the trees are home to, fear because the Alder groves, growing on marshy, boggy ground, are places where it is easy to get lost and fall into the mire, sometimes never to escape. Those that sank into the swamps never to see the light of the day again, are believed to haunt the groves and so the fear of the Alder groves grew.
But for those that know the Alder groves well, they are a place to hide, a place of concealment and a place of enchantment. The folk of the Fae dwell here exactly because it is a place of concealment, a place to be undisturbed by the world of man and so for those lucky enough to be safely admitted, it is a place of enchantment.
The flowers of the Alder tree give a vibrant green dye; the green dye said to be that used by the Fae to dye their clothes and which enables them to hide from the sight of man. Because of this, outlaws like Robin Hood used the dye for their clothes to give them concealment.