How do the Kellers commemorate their son Larry's death?

The Kellers commemorate Larry by planting a tree in their backyard. At this stage he's missing, presumed dead, but no one knows for sure what has happened to him. The tree comes to take on great symbolic significance throughout the play. When the tree is severely damaged in a storm, Larry's mother Kate interprets this as a sign that the Kellers have forgotten him and effectively given up hope of ever seeing him again. Ironically, a tree planted to keep Larry's memory alive has become, in Kate's eyes, a symbol of forgetfulness.
In any case, Kate recognizes that a memorial for someone she still believes to be alive and well is completely false. As for ourselves, we can perhaps interpret the storm as representing an attack of the natural upon a symbol of the supernatural. The destruction of the tree shows that that is all it is: a tree, and nothing else. It cannot then be used as a symbol of hope and expectation, which transcend the world of nature in which we all must live.

All My Sons is a play by the well-known and influential playwright Arthur Miller. The piece focuses on the Keller family and those around them as they try to move on from loss and uncover terrible truths about past choices made by their patriarch, Joe Keller.
Pretty early on in the play we learn that the younger of Joe and Kate Keller's two sons, Larry, went missing during World War II and is now assumed to be dead. While Kate does not let herself believe that Larry is dead, even after three years of him being gone, the family planted an apple tree in their yard as a memorial to him. Before the beginning of the play, the tree has been destroyed by a storm and is now just a stump with its trunk and limbs "toppled beside it, fruit still clinging to its branches." This event gets a variety of reactions from the Kellers. For example, Kate takes it as a confirmation that Larry is alive and becomes upset, saying that they "should never have planted that tree" and that "Everybody was in such a hurry to bury him." Speaking in terms of dramatic structure, the destruction of this tree foreshadows the impending disturbance in the lives of the characters.