Casting her text into verse to no obvious purpose or benefit, Kudlinski offers only a partial answer to the title question. Bypassing such topics as the role of roots in absorbing nutrients, how they fit into underground ecosystems and much besides, she confines herself to four points: They hold plants in place; take in water; will “probably” kill the plant if broken off; and are sometimes edible. Though his smiling young gardeners are awkwardly drawn, Schuppert does offer artfully angled cutaway views of lush flowers and foliage above, spreading root systems below—providing some visual appeal while effectively showing that there’s more to plants than meets the eye. But younger naturalists will absorb more from the likes of Allan Fowler’s Taking Root (2000) or the plethora of more widely focused accounts of how plants grow. (Picture book/nonfiction. 5-7)