Rowan

Sorbus aucuparia. Also known as "quickbeam" and "mountain ash", this hardy tree is much used in the US and Europe as a city tree because of its resistance to air pollution and other environmental abuse. Its white or pink flower in the spring and its bright red berries (which often last right through the winter if the birds don't eat them all) make the rowan tree extremely popular as an ornamental.

But wizards have more reasons to appreciate rowan trees than just their aesthetic qualities.