Warner was a lover of nature. While growing up, she had butterfly and moth collections, pressed wildflowers, learned of all the birds in her area, and kept a garden. She used these interests in teaching her grade school students, and also used nature themes in her books. For instance, in the second book of "The Boxcar Children (Surprise Island)," the Alden children make a nature museum from the flowers, shells and seaweed they have collected and the shapes of birds they have observed. One of her students recalled the wildflower and stone-gathering contests that Warner sponsored when she was a teacher.