After Mortimer takes a plant home from his 3rd grade classroom during summer vacation, strange things begin to occur. Plantzilla begins to grow tentacles and perform miraculous feats. Mortimer's parents begin to worry as they see the plant take on human characteristics, but Mortimer's love for Plantzilla grows even deeper. Written in letter-form, the text is a series of communications between Mortimer and his teacher, and the teacher and Mortimer's mother regarding the progress and concerns of this unusual plant. This humorous story contains beautiful watercolor illustrations that spill across the page and engage the reader.