Instead of gravestones (like humans traditionally use), the elves plant a Wanderling seed with the deceased person's hair wrapped around it. When the tree grows from the seed it will resemble physical characteristics of those who passed away. For example, if you had blue eyes and light hair, the tree might have blue flowers and light bark.
The Wanderling Woods are described as a very quiet place with not even the sound of birds. Each grave has a unique tree based on the person's DNA. There is a golden archway with white flowers and the words, "Those Who Wander Are Not Lost," a saying that Sophie notes to be quite similar to a saying written by J.R.R. Tolkien in his series The Lord of the Rings (more specifically from a poem in The Fellowship of the Ring).
There is a wanderling seed that is wrapped with a strand of hair from the deceased person for DNA (although it is assumed that if hair is not available, any other source of DNA from the dead elf would be sufficient). When it is planted, the tree will grow, absorbing the DNA and resembling the deceased, taking on features of the person in the form of leaves, flowers, and such. Trees and Graves
Cyrah Endal- Her tree is a willow with red leaves and small, purple flowers. Her tree was planted when people thought she died from a leaping accident, but she was actually murdered by Gethen under Fintan's orders before the beginning of the series.
Dexter Alvin Dizznee (still alive)- His tree has a twisted trunk, spiky red leaves, and periwinkle berries. It has grown twice as tall as Sophie's tree and has periwinkle flowers that smell bad. His was planted when he and Sophie were kidnapped in Book 1: Keeper of the Lost Cities.
Jolie Ruewen- Her tree is graceful and wispy, pale, with large, turquoise blossoms. The leaves are green with yellow Spanish Moss. It smells like sugar and honey. Within the branches is a charm bracelet that Grady and Edaline gave to her while Jolie was still living. They add charms every year on the anniversary of her death. In Exile, Edaline and Grady bring a special solution made by the gnomes that causes a glittering, purple-flowered vine to grow around the tree.
Sophie Elizabeth Foster (still alive)- Her tree is described as pale and scrawny, with golden, star-shaped leaves and brown bean pods. Grady and Edaline also brought her a charm bracelet in which they placed an elephant charm (most likely inspired by Ella) when they thought she was dead. Sophie's tree is thought of as plain despite her role in the series. Sophie thinks this is because of her altered DNA.
Mr. Forkle (One of the twins) - His tree reflects his multiple identities, and leans slightly as if waiting for its counterpart. Mr. Forkle has a twin, under the same name, and his who died in Lodestar. His tree was not planted in the Wanderling Woods, as to not raise attention to his death, and was planted in Norway.