Mallorn (S. ‘gold-tree’; plural: mellyrn) was the tree of Lórien: its bark was grey or silver, and its blossoms golden. These leaves turned to gold in the autumn but did not fall until the beginning of spring; at that point, the Wood was carpeted and covered in gold, hence it being known as the Golden Wood. It was atop these trees that the Galadrim built their telain.
While mellyrn were found nowhere else in Middle-earth, a new tree appeared early in the Fourth Age: this tree was grown by Samwise Gamgee, who had been given a single mallorn-seed by the Lady Galadriel. It was planted in the location where the original Party Tree had once been.