The tree is an important object from Speak that has symbolic meaning.
The tree is very important to Melinda's freshman year. When Mr. Freeman asks students to pull random pieces of paper that will serve as their art project, Melinda pulls the paper that has "tree" on it. She wants to put it back. As with so much in her freshman year, Melinda has little faith that it will work out. The early going proves her right. Melinda struggles to create her tree. This is symbolic of Melinda's freshman year, in general, where she struggles to find her place and find any happiness. There is a trial and error process as Melinda creates her tree. Sometimes, it's too simplistic, symbolic of Melinda's friendship with Heather. Other times, it's too formulaic, representative of how school officials and Melinda's parents want her to behave.
As the year progresses, trees come to symbolize Melinda's own growth and development. For example, when Mr. Freeman offers feedback on her tree, he is speaking for more than the tree:
This looks like a tree, but it is an average, ordinary, everyday, boring tree. Breathe life into it. Make it bend—trees are flexible, so they don't snap. Scar it, give it a twisted branch—perfect trees don't exist. Nothing is perfect. Flaws are interesting. Be the tree.
Melinda's need to "be the tree" is symbolic of how she has to overcome the challenges that plague her. She must be willing to live with the "scar" of what happened to her and be "flexible" to avoid snapping entirely. Like her art, Melinda's growth goes through phases:
My tree is definitely breathing; little shallow breaths like it just shot up through the ground this morning. This one is not perfectly symmetrical. The bark is rough. I try to make it look as if initials had been carved in it a long time ago. One of the lower branches is sick. If this tree really lives someplace, that branch better drop soon, so it doesn't kill the whole thing. Roots knob out of the ground and the crown reaches for the sun, tall and healthy. The new growth is the best part.
In her first year of high school, Melinda finds her voice in "new growth." Challenging Nicole in tennis, facing down Mr. Neck's unfairness regarding her suffragette report, taking it upon herself to clean and maintain the yard, breaking through her own silence to warn others of "IT," and then personally speaking to Rachel/ Rachelle about it show how "roots knob out of the ground and the crown reaches for the sun." The growth of Melinda's tree in art is symbolic of her emerging voice.
Trees occupy a symbolic importance in Speak even outside Melinda's own artwork. For example, when her father talks about why a tree is being chopped down, it is symbolic of the life Melinda must lead:
He's not chopping it down. He's saving it. Those branches were long dead from disease. All plants are like that. By cutting off the damage, you make it possible for the tree to grow again. You watch—by the end of summer, this tree will be the strongest on the block.
While Melinda dismisses her father as "pretending to know more than he does," his words do symbolize Melinda's own struggle. She must save herself by "cutting off the damage." When Melinda fights back against Andy and defeats him, it is clear that she has become "the strongest on the block."
From "pruning" to "final cut," the tree symbolizes the arc of Melinda's development. When she is finished with her tree, she sees it as a symbol of her own life: "I look at my homely sketch. It doesn't need anything. Even through the river in my eyes I can see that. It isn't perfect and that makes it just right." The tree is a symbol from Speak that represents how growth is an essential part of Melinda's life.