The word "tree" is Sal's middle name. We're not joking. Trees are part of her and she is part tree. Not only that, but we hear a lot about trees in her story. She loves them. She is in awe of them, almost as though they have superpowers.
Let's take a look at some of Sal's encounters with trees. That just might help us understand what they mean to her.
Hmm, let's see. There's the singing tree in Bybanks. Remember that one?
Next to my favorite sugar maple tree beside the barn is a tall aspen. When I was younger, I heard the most beautiful birdsong coming from the top of that tree. It was not a call; it was a true birdsong, with trills and warbles. I stood beneath that tree for the longest time, hoping to catch sight of the bird who was singing such a song. I saw no bird – only leaves waving in the breeze. The longer I stared up at the leaves, the more it seemed that it was the tree itself that was singing. (16.10)
This tree totally does have superpowers – it can sing! And what a beautiful song it is. Sal revisits it time and again, listening for that song. When she and her father learn that her mother is not coming back, the tree does not sing.
Oh, and there are all those trees all over the place to which Sal has given blackberry kisses. We can't forget those. It's almost as if all these trees have minds of their own. Sal sees them like living creatures with brains and feelings, and she wants to be closer to them. She even prays to them, especially when she's on that scary drive to the site of the bus crash. She's so frightened, she tells us, that she "prayed to every passing tree, and there were a thumping lot of trees along the way" (41.22).
Finally, when she visits her mother's grave in Coeur d'Alene, she hears a songbird. She realizes the singing bird is somewhere in a willow tree next to her mother's grave. She kisses the willow tree and says, "happy birthday," as though her mother's spirit were now resting in that willow tree. And we readers, of course, think back to that singing aspen on her farm in Kentucky, the one that wouldn't sing after her mother left.
It's clear that, to Sal, trees are more than just beautiful things to wonder at. Trees are a huge part of nature, and Sal's family loves nature. They are farmers. They work with the earth. They kiss trees. Nature is pretty much the bomb in the Hiddles' eyes.
But nature is not always kind. Just like life, nature can be cruel. You could argue, for example, that nature is responsible for the fact that Sal's mom leaves. If Sal hadn't fallen off a tree while climbing it, her pregnant mother wouldn't have strained herself to save her and might not have lost the baby.
Still, we can't help but see trees as ultimately good. And we think that's how Sal sees them, too.