Oliver is a proud plant-grafter and scientist who uses his verdant know-how to help his community by pairing all his neighbors with the most useful plant. He grows the Climatis Enduris for Mr. Finch to keep him dry, the Housum Immaculatis to help Mrs. Kulp stay on top of her chores, and the Shrub Architectis for Ms. Lloyd to keep her dog fenced in.

But Oliver's trickiest customer is Mrs. Kroftombottom, who cannot keep a plant alive no matter how hard she tries. Oliver makes it his mission to grow some greenery that she can maintain, using the scientific method to determine what's gone wrong in her garden. Can he unlock the secret ingredient that will allow her plants--and Mrs. Kroftombottom herself--to flourish?