Herbarium: The Quest to Preserve and Classify the World’s Plants by Barbara M. Thiers. Portland, OR: Timber Press; 2020. ISBN: 978-1-60469-930-2. Hardcover, 304 pages. $40.00.

This elegantly written and lavishly illustrated book takes readers through time and place in an exploration of how herbaria (collections of preserved plant specimens used for scientific study) were first created as simple teaching tools, to their evolution as essential scientific resources that document the world’s plant and fungal biodiversity and help shape our response to global change. Luca Ghini (1490–1556), an Italian physician who received his medical degree from the University of Bologna in 1527, is recognized as the first to use dried, pressed plants in his university teaching. At that time, medicine depended heavily on plants, and physicians who used these modalities were also trained in botany. After all, the misidentification of a plant that a physician prescribed for a common condition could, in the worst case, lead to the patient’s death. Ghini was the first person who is documented to have taught a medicinal plant course in a European medical school. He realized that he could not always depend on book illustrations to identify medicinal plants, so he began to use living plants in his classes, giving medical students the opportunity to touch, smell, and taste the therapies that they would be prescribing.

But in winter, many living plants were unavailable, so his bold step was to create an herbarium of dried, pressed, preserved plants, first known as a Hortus Hiemalis (winter garden) or Hortus Siccus (dry garden). His technique was to take fresh plants and arrange them on paper to simulate, to the extent possible, the way they looked in nature. Then he dried the plants by applying pressure on the specimens to release the moisture these materials contained, resulting in flattened dried plants, many of which retained an element of their original colors. When properly dried and preserved, the specimens were glued onto the pages of a blank book, in which Ghini could write notes about the plants to further inform his students. Plants prepared this way and properly curated (e.g., kept from moisture, high temperatures, and insects) will last almost indefinitely. These newly created resources were far more valuable to medical professionals than the simple illustrations in medical books of the day. Ghini then went on to teach at the University of Pisa, where he created the first known botanical garden for the purpose of training physicians. Known as the Orto Botanico di Pisa today, this historically significant garden is open to the public, free of charge. From their initial use in teaching medical students, preserved plant collections now known as herbaria can be found around the world, furthering our understanding of botanical diversity.

Readers may remember a childhood school assignment to collect colorful leaves in the fall and press them between paper, so they could be observed with delight and studied. With this assignment, students made an herbarium specimen, although not always with the scientific rigor necessary for proper use of the material.

This book is an extraordinary and most engaging tour of the history of botany and the establishment of herbaria. It covers botanical exploration and the remarkable and sometimes unexpected personalities who expanded our understanding of the diversity, beauty, uses, and distribution of plants and fungi. The next sections of the book discuss the development of herbaria in the United States and around the world. The final section is devoted to the future of herbaria and the relevance of these natural history collections that now hold and carefully curate an astonishing total of about 390 million individual specimens. With new technology, scientists are putting these collections to use in ways unimagined by Ghini, using data to understand global change, classifying plants by analyzing their DNA, detecting and remediating pollution, documenting and predicting threats from invasive species, and understanding atmospheric conditions of the past, all through use of these specimens. Those in the herb and supplement industries, or people who simply admire and use plants in their daily lives, will find this an important resource. This book gives life to botanical collections and is a brilliant work that can be read, understood, and enjoyed by everyone.

Michael J. Balick, PhD, is an ethnobotanist at the New York Botanical Garden, specializing in diversity, distribution, and traditional uses of plants.