Set in the peaceful valley of Ombrosa during the period of intellectual and social ferment which characterized the Age of Reason, Italo Calvino’s The Baron in the Trees relates the story of Cosimo Piovasco di Rondo, heir to the immense estate of the Piovasci. Cosimo rebels against the rule-burdened atmosphere in which he is reared by climbing into the trees on his family’s estate at the age of twelve and remaining there for the rest of his life. His refusal to eat the snail soup and main course of snails prepared by his sister Battista is the issue which sends him into the trees, but he soon decides to make them his permanent home.
Cosimo’s family makes a few perfunctory attempts to get him down. His mother, nicknamed "the Generalessa" because of her Austrian military ancestry, worries at first about Cosimo’s falling. (His brother Biaggio, who becomes both observer of and commentator on Cosimo’s unusual way of life, finds this concern ironic, noting that it would not have bothered their mother in the least to see her sons under cannon fire.) Eventually, she rather enjoys catching sight of Cosimo in one tree or another through her telescope, and she sends him messages with her military signal flags.
Cosimo’s varied adventures in the trees make for enjoyable reading. At first these are boyish pranks, such as throwing a piece of bark at the boys’ pompous tutor, the Abbe Fauchelfleur, or hair-raising encounters with the "fruit thieves," neighborhood boys who steal from the lush orchards in the area. One experience, however, has a lasting effect on Cosimo: meeting Violante (Viola) Ondariva. Their families have not spoken for years, but within minutes they are fast friends, and Viola is taken with Cosimo’s unusual way of life. She even helps him escape from the fruit thieves in the guise of "Sinforosa."
Though Cosimo is a solitary figure, he does not avoid people. Indeed, as he matures, he provides useful services such as delivering messages. His agility allows him to pass easily from one tree to another, and, since he is bound by neither walls nor fences, he can travel great distances quickly. When huntsmen lose their quarry, he directs them to the fox. His perspective allows him to see which streams are best for fishing, and he often dangles his line from a convenient low-hanging branch. He finds it difficult but does, at least at first, attend High Mass by kneeling on a limb which is at the same height as a large church window.
Cosimo becomes close friends with his father’s illegitimate brother, Cavilier Enea Silvio Carrega, who is also the family lawyer. Carrega is a secret beekeeper with beehives scattered throughout the valley. Cosimo helps him to gather bees and to devise a grandiose but unrealized scheme for irrigating the neighboring farmland. It does not bother Cosimo that the irrigation project never comes to pass. He realizes that tending the hollowed-out tree trunks that would carry the water would eventually prove a burden, binding him more closely to the earth. Escaping the burdens of everyday life was, after all, one of Cosimo’s primary reasons for living in the trees.
Carrega has lived a life of secret resentment for many years. The Piovasco estate, where he lived as permanent houseguest, is the grandest in the valley, but no share of this wealth could ever be his since he is illegitimate. His smuggling activities, eventually revealed by Cosimo in a way that does not tarnish Carrega’s reputation, represent a desperate attempt at revenge. Cosimo, by contrast, feels none of these burdens. Though heir to the Piovasco estate and fortune, and though reconciled at last with his father, he assigns all of his rights to his mother and brother. In return he receives a stipend adequate for his own maintenance, regular consignments of books by the authors he most enjoys, and the affection of many who live in the region.
In many respects Cosimo enjoys a surprisingly normal life in the trees. Though alone, he is rarely lonely. He meets a kindred spirit in Ursula, daughter of a noble exile from Charles III’s Spain, Federico Alonso Sanchez y Tobasco. Federico’s court has been granted permission to pass through northern Italy but only on the condition that they do not set foot on the earth. The entire entourage thus becomes tree-dwellers, though, unlike Cosimo, not by choice. Ursula desires to remain with Cosimo in the trees even after her family receives permission to return to Spain. She obediently, though reluctantly, accompanies them at last. Cosimo accepts this philosophically, as he does all human relationships, recognizing that all things end and pass away, even what one most treasures.
Cosimo lives in the trees well beyond the age of sixty-five and does not come down though he becomes old and infirm. His death, as unusual as his life, presumably occurs when he grabs hold of an anchor fastened to a passing hot-air balloon. Thus Cosimo’s body, though of the earth, never returns to it again.