Mellyrn are trees of immense size, especially when growing on Númenor. They are also described as similar to birches: their bark was smooth and silver-grey, and the leaves were green on top and silver underneath; they turned golden in autumn and remained on the tree through the winter to fall to cover the ground in the spring, when new leaves sprouted. Golden flowers bloomed on the branches.
The trunk of the tree divided to a crown of many branches, and the Galadhrim used the space to build telain (a sort of platform) or buildings on the top of the trees. The leaves also had practical uses, such as for packing rations of lembas.
Mallorn-trees originally grew in Valinor and from there were spread to Tol Eressëa by the Elves once the Lonely Isle was moved to its final position by Ulmo. The Elves of Tol Eressëa brought mallorn-trees to the Men of Númenor and they grew on the shores around the Bay of Eldanna in that land. Even Tar-Aldarion, the great Ship-King, did not cut down these trees.
Mallorn-nuts were given by Tar-Aldarion to his friend Gil-galad, the Noldorin King of Lindon. The mellyrn did not grow in Lindon, but Galadriel took some nuts with her to Lothlórien, where they grew to immense heights (but not as great as the groves of Númenor). Lothlórien became known as the Golden Wood because of them.
Caras Galadhon, the city of Galadriel and Celeborn in Lothlórien, was built in the branches of huge mallorn-trees. The Fellowship spent the night in a flet in a mallorn-tree nearby, and were later given lembas wrapped in mallorn-leaves.
Galadriel gave Samwise Gamgee a box of soil containing a single silver mallorn nut. After the War of the Ring and the Scouring of the Shire, Sam planted the nut in the Party Field where the Party Tree had stood before its felling. It was the only mallorn-tree in Middle-earth outside of Lórien. When the tree bloomed in the next summer it was said that all the Shire became golden from the flowers.
 Uses outside the Legendarium
 Portrayal in adaptations
- Mallorn trees are the core buildings in the elven faction, as they produce resources needed for constructing buildings and recruiting troops. When a mallorn tree reaches level 3, a tower is automatically constructed atop of the tree, where an elven archer is placed.
- ↑ 1.0 1.1 See Letter to H. Cotton Minchin (16 April 1956)
- ↑ 2.0 2.1 2.2 J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "A Description of the Island of Númenor"
- ↑ 3.0 3.1 J.R.R. Tolkien, The Lord of the Rings, The Fellowship of the Ring, "The Mirror of Galadriel"
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Fellowship of the Ring, "Lothlórien"
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "The History of Galadriel and Celeborn", "Concerning Galadriel and Celeborn", note 5
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Fellowship of the Ring, "Farewell to Lórien"
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Return of the King, "The Grey Havens"
- ↑ J.R.R. Tolkien, "The Rivers and Beacon-hills of Gondor" (edited by Carl F. Hostetter), in Vinyar Tengwar, Number 42, July 2001, p. 27
- ↑ Carl F. Hostetter, The Two Phonetic Values of ll in Elvish Sindarin in The Lord of the Rings, published on Tengwestië, December 7, 2003
- ↑ J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "A Description of the Island of Númenor"