Instruct: Classify a given review as either positive or negative.
Query: Authoritative, easily understood introduction to daylilies

Diana Grenfell's guide to growing daylilies covers daylilies from 551-479 BC to the present. She clearly presents a broad view of this beloved perennial, with excellent insight. From cultivating to breeding, terminology to forms, colors and cultivar recommendations, this book is as good as there is on the subject of daylilies.