Rinse the wheat berries in a strainer and put them in a pot over water overnight to soak. Rinse and drain them and put them back in a pot of water, covered by at least 2 inches of water. Bring to a boil, reduce the heat to medium and simmer for about an hour until tender but not mushy and still completely intact. The wheat berries should still be a little chewy. Drain thoroughly and place in a large bowl. Let them cool completely.
Toast the walnuts by placing them whole in an oven preheated to 375 degrees F and toast them for 5-10 minutes until fragrant, being careful not to scorch them.Place the ingredients for the vinaigrette in a small bowl and whisk to combine.
Add the remaining salad ingredients to the wheat berries and stir to combine. Add the walnuts and stir to combine. Pour the vinaigrette over the salad and stir to combine. Cover and refrigerate for at least two hours before serving, stirring occasionally to distribute the vinaigrette.