According to The Herb Society of America's New Encyclopedia of Herbs and Their Uses by Deni Bown:
"The term "herb" also has more than one definition. Botanists describe an herb as a small, seed bearing plant with fleshy, rather than woody, parts (from which we get the term "herbaceous"). In this book, the term refers to a far wider range of plants. In addition to herbaceous perennials, herbs include trees, shrubs, annuals, vines, and more primitive plants, such as ferns, mosses, algae, lichens, and fungi. They [herbs] are valued for their flavor, fragrance, medicinal and healthful qualities, economic and industrial uses, pesticidal properties, and coloring materials (dyes)."
© Deni Bown, 2001.
Citation: Bown, Deni. The Herb Society of America New Encyclopedia of Herbs and Their Uses. New York: Dorling Kindersley, 2001. p. 18.
Posted on the New England Unit's web site with permission.
