Last May, when I began the first of two courses with William (Bill) Cullina, the President and CEO of the Coastal Maine Botanical Gardens, the student sitting next to me in class had a copy of his book Understanding Perennials: A New Look at an Old Favorite (Houghton Mifflin Harcourt, 2009) with her and noted that many of the images he was showing as part of his lecture were in the book. I already had Understanding Perennials on my “wish list” at the public library; that night when I got home, I put a hold on it and picked it up within the week. By the time I had finished the first chapter, I had gone online to buy my own copy; by the time I had read half of it, it had become one of my top five favorite garden books.
Cullina sets the scene in Understanding Perennials by positing the world of plants as an alien culture and gardeners as “immigrants to the kingdom of plants.” Some gardeners are like tourists who never make much of an effort to learn the language or culture of the place they are visiting, “developing a rude sort of horticultural sign language that depends heavily on conjecture and leaves more than a fair share of casualties….” Others are more like permanent residents who are trying to assimilate, “learning some of the basic customs and phrases from gardening books and university night classes.” Only a rare few truly immerse themselves in the alien culture, becoming as fluent as native speakers and really understanding plants. (pp. 4-5) Cullina seems to believe that most of his readers will be in the second group, and his goal is to help us move closer to true immersion in the culture of the plant kingdom. The problem, as he sees it, is that we are usually trying to learn about this kingdom and its culture from other immigrants, but the best teachers are the natives (plants themselves). He is convinced that the best tool for learning from plants is science, but that many would-be students are thwarted by the arcane language and densely complex prose of science. This book is intended to be a kind of cultural broker.
What I have aimed for is a work that translates the language and culture of plants and the language of science into words and concepts we can understand, and to do it with as much clarity, poetry, and purpose as I can muster.” (p. 9)
Understanding Perennials does not shy away from the language of science; after all, Cullina’s mission is to make us more comfortable with a scientific understanding of plants. But he tries to use scientific terminology in ways that will not alienate a lay reader. Key terms are collected in a four-page glossary at the end of the book. In the main text, they are always set in a context of language and images familiar to a gardener. Cullina makes horticultural science personal by tying it to his own experiences in his own garden and in the greenhouse at Garden in the Woods (where he was in charge of plant propagation before he came to Coastal Maine Botanical Gardens) and to his own experiments with plants. The book is chock-full of full-color photographs, and these images also make the lay gardener feel at home. But these are not just pretty pictures of pretty flowers in attractive settings. A series of images on page 35, for example, documents an experiment in which Cullina deprived a heart-leafed aster (Symphyotrichum cordifolium) of water and recorded what happened to the roots and the above-ground plant as it dried out – a powerful lesson about how drought damages a plant and why it may not recover immediately when it rains. In another example of science made accessible, an infrared photo of a potentilla flower on page 111 shows us the color patterns that a bee can see but that human eyes cannot.
Cullina also makes horticultural science accessible by tying it to personal experience and family life. A discussion of aphids, for example, includes the following;
Aphids are primarily after the protein in the phlom [sic], so most of the sugars are processed and secreted out their rear in the form of honeydew – as euphemistic a word for excrement as you are likely to hear. The next time I change the twins’ diapers, I’m going to call it “collectin’ the honeydew.’’
The structure of Understanding Perennials takes us from a chapter that introduces and defines perennials, differentiating them from annuals in growth and reproductive cycles, through a series of four chapters (on roots, leaves, stems, and flowers and seeds) that examine the anatomy and physiology of perennials, to chapters about gardening with perennials (on pests and diseases, botanical names, garden design, using cultivation methods that understand how plants interact with their environments, and methods of propagation). This is indeed an “owner’s manual” for perennials, and it is a book that no gardener who seriously wants to understand perennials should be without.
Filed under: favorite books, Garden Books, garden science, plants Tagged: Coastal Maine Botanical Gardens, Garden Books, horticultural science, perennials, William Cullina 
