Cook sweet potatoes in boiling water to cover 25 to 30 minutes or until tender; drain and cool. Peel sweet potatoes, and cut into 1/2-inch-thick slices. Cut apples into thin wedges; slice green onions.
Arrange one-fourth of sweet potato slices, apple wedges, and green onions in a large salad bowl; drizzle with one-fourth of Poppy Seed Dressing. Repeat layers 3 times with remaining ingredients; chill.