Rodale's 21st-Century Herbal: A Practical Guide for Healthy Living Using Nature's Most Powerful Plants



What are herbs? To a botanist living in the temperate region, an herb is simply an herbaceous plant—that is, a plant that does not produce persistent woody tissue and usually dies back in winter. Height isn’t a factor. One of the largest herbaceous plants, the banana—which does not produce a woody stem, but rather a fleshy “pseudostem”—can grow to 20 feet tall or more.

To a chef, the definition is completely different: An herb is any of a vast number of aromatic or savory plants used to add flavor and character to foods. To a gardener, an herb is a delightful, easy-to-grow addition to the landscape, perennial border, or terrace urn. And to anyone who uses plants medicinally, an herb is a plant or plant part that helps promote health and healing when it’s either taken internally or applied externally.

Yet none of these definitions wholly describes the many attributes of an “herb.” The botanist’s definition of an herb—any “nonwoody” plant—does not encompass many plants known today as “medicinal herbs” or “botanicals.” Medicinal herbs come from all kinds of plants: trees, shrubs, vines, grasses, and ferns—as well as mushrooms, lichens, mosses, and seaweeds. The chef’s emphasis on flavor does not address the powerful medicinal properties of many common culinary herbs, such as garlic, ginger, turmeric, and cayenne. And the ornamental gardener does not consider the value of dandelion for cooking, healing, or making dyes—she’s far more likely to dig out this herb as a “weed” than to plant it.

So just what is an herb—a nonwoody plant, culinary staple, garden ornamental, health-promoting remedy, or a weed? The answer is all of the above, depending on the plant and how it is used. Indeed, usefulness could be the most defining characteristic of an herb: An herb is a plant that humans use, or have used, to enhance their lives.


A rose is a rose is a rose? If only it were that simple! The truth is, most well-known plants go by several names: a scientific name and one or more common (or vernacular) names, depending on where the plant is found or grown. Making matters more confusing, a single common name can often refer to plants of several different botanical species. For instance, in the United States, “corn” is the common name for Zea mays, the vegetable enjoyed “on the cob.” Say the word “corn” to a farmer or baker in England, and they will think you are speaking about wheat (Triticum spp.). In Scotland, “corn” might refer to oats (Avena sativa).

The common name, as the term implies, is a name people coin to identify a local plant—for example, sweet violet, catnip, and dandelion are common names. Often, common names are colorfully descriptive, and they can provide valuable information about a plant’s traditional uses, characteristics, or growth habits. The name dandelion, for example, comes from the French dente de lion, which means “tooth of the lion” and describes the serrated edge of the leaf. Another common French name for dandelion, pis en lit, translates as “wet the bed,” a reference to the powerful diuretic properties of the dandelion leaf.

Botanically speaking, sweet violet, catnip, and dandelion are known as Viola odorata, Nepeta cataria, and Taraxacum officinale, respectively. Just like common names, botanical names offer fascinating clues about what plants look like, what they smell like, where they come from, and even how they are used medicinally. Using the same three plants as examples, it is possible to infer from the species name odoratathat this violet has a distinctive fragrance. The name cataria indicates that this member of the genus Nepeta is linked in some way to felines. And the name officinale (or officinalis), which originally referred to a monastic storeroom or pharmacy, is an indication that a plant was utilized as a medicine based on its healing properties.

Sweet violet has several common names, including wood violet or English violet. But it has only one correct scientific name: Viola odorata.


Although a plant might have several common names, it will have only one officially recognized botanical or scientific name. The advantage of using botanical names, or scientific nomenclature, is that it allows one—no matter what his or her native tongue—to understand exactly which herb is being discussed. For example, the spiny shrub Eleutherococcus senticosus—commonly called Siberian ginseng or eleuthero in the United States and devil’s shrub or thorny pepper bush in Russia—is understood to be Eleutherococcus senticosus whether one is a citizen of the United States or Russia. This is an important and basic standard, not only to botanists and other scientists, but also to herbalists, practitioners, and members of the botanical trade, who need to be absolutely certain about the identities of the plants they use.

Early plant scientists recognized the need for a system of terms that could be used to distinguish one particular plant species from all others in the world. This task was successfully accomplished by the Swedish botanist Carolus Linnaeus (1707–1778), who in 1753 established what’s known as the binomial system of plant nomenclature. Linnaeus’s goal was to name and describe all known types of plants, as well as animals and even minerals. He believed that in so doing, he would reveal the grand pattern of creation. In a two-volume work called Species Plantarum, Linnaeus introduced a workable botanical classification system that would eventually bear his name.

Scientists quickly adopted Linnaeus’s system as a means of sorting out the vast numbers of new species being discovered at the time. Nearly 20 years before publishing Species Plantarum, Linnaeus proposed a polynomial (multiple-word) naming system to describe species, but in later editions of his works, this evolved into the basic binomial (two-word: genus and specific epithet) naming system used today. The Linnaean system of classification is based on relationships among living organisms, from the most general (kingdom) to the most specific (species). A species, the most basic unit of organization in the system, is composed of individuals that resemble one another more nearly than they resemble individuals of any other species.

Originally named Bromelia comosa by the Swedish botanist Linnaeus, the pineapple plant was renamed Ananas comosus by Elmer Drew Merrill in 1917.

Using the plant Ginkgo biloba as an example, Ginkgo is the genus name and biloba is the specific epithet. In more formal use, such as in a scientific paper, the name of the botanist who first described the plant is also included. For example, Ginkgo biloba was described by Linnaeus, which is noted as part of the scientific name following the species: Ginkgo biloba L. And over time, if a different botanist decides that the plant belongs to another genus, then the original author’s name is put in parentheses, with the later author’s name following. For example, the scientific name of the pineapple is Ananas comosus (L.) Merr. While this wonderful fruit was first described by Linnaeus as Bromelia comosa L., in 1754, the species was moved to the genus Ananas by the renowned Pacific botanist Elmer Drew Merrill in a 1917 publication. Nearly 100 years later, the term Ananas comosus is still used to describe the pineapple plant.

But that’s not the case with all species. As our understanding of relationships among plant species and among plant families becomes more sophisticated, plants are moved into more precise alignments based on their evolutionary position in the “tree of life.” In this book, to simplify the binomials, we will not include the botanist’s names. If you are interested in this element of botanical history, the names and stories of the scientists who first applied them can be found in many other books and on the Web.

Far from static, these classifications change as new information alters scientists’ understanding of the relationships among organisms. Originally, all organisms were classified into two kingdoms: animal and plant. Now, based on information such as data obtained by molecular studies unavailable when the Linnaean system was introduced, most scientists use a six-kingdom classification scheme that separates fungi and certain other kinds of creatures into kingdoms of their own. Increasingly, biologists are recognizing a new rank—domain—above the grouping of kingdom. There are three domains: Bacteria, Archaea, and Eukarya. Herbs belong to the domain Eukarya, which contains animals, plants, fungi, and protists.


The kingdom is the largest, most inclusive classification in the Linnaean system. Most scientists recognize these six kingdoms: Animalia (animals), Plantae (plants), Fungi (fungal organisms, including mushrooms), Protista (simple organisms, such as protozoans and algae, whose cells have nuclei and organelles), Archaea (single-celled microorganisms with cells that do not have nuclei or organelles and that do not carry out chlorophyll-based photosynthesis), and Bacteria (single-celled organisms with cells that do not have nuclei or organelles; some species carry out chlorophyll-based photosynthesis).

Within the plant kingdom, organisms are sorted into angiosperms (plants with seeds enclosed in an ovary), gymnosperms (“naked seed” plants), ferns, fern allies, mosses, liverworts, and hornworts. Recent classification systems based on a more precise understanding of plant relationships and evolution refer to groupings as clades (see “A Modern Understanding of the Plant Kingdom”), signifying branches on the tree of life and, to a degree, they dispense with certain elements of the Linnaean system.


Groups of related genera make up plant families. Some plant families are quite large—the orchid, aster, and pea families are the three biggest—while others, such as the ginkgo family, contain only one species.

In an ongoing effort to standardize the classification and naming of plants, botanists in recent decades have modernized the naming of plant families. According to the current system, family names end with the suffix “-aceae” and are taken from the name of an included genus that typifies the family. (Genus and species names are italicized in print, but family names are not.) For example, Acorus calamus, sweet flag, is a member of the plant family Acoraceae. Plant families also are sometimes referred to by the common name of a genus associated with that family, such as “rose family” (for Rosaceae). So, while the English hawthorn (Crataegus laevigata) is not of the same genus as garden roses (Rosa spp.), as a member of the Rosaceae, it shares “rose family” traits, along with species of the genus Prunus, where plums, peaches, and apricots are found. However, there is no standardized list of common names for plant families, and some families are referred to using various names. For example, common names for the Marantaceae, a group of tropical species, include the prayer plant family and arrowroot family. And the Asteraceae is known variously as the daisy, sunflower, or aster family.

Botanists have agreed upon protocols for naming plants, known as the rules of nomenclature. For eight plant families, alternative family names are permitted under the current rules: These alternatives are (with modern equivalents in parentheses) Compositae (Asteraceae), Cruciferae (Brassicaceae), Gramineae (Poaceae), Guttiferae (Clusiaceae), Labiatae (Lamiaceae), Leguminosae (Fabaceae), Palmae (Arecaceae), and Umbelliferae (Apiaceae).

Some plant families are so large and complex that they are further divided into subfamilies and what botanists call “tribes.” The sunflower family (Asteraceae), one of the largest of all plant families, at one time was subdivided into two subfamilies. But now, after much more sophisticated analysis of the evolutionary relationships of this group, it is considered to have 12 subfamilies. Such distinctions are not always clear-cut, and botanists continue to study and refine our understanding of plant relationships and how species should be classified.


A genus consists of a group of species closely related to one another, determined primarily by the reproductive parts of their flowers. Some of the many genera in the mint family (Lamiaceae) are Lavandula(lavender), Mentha(mint), Thymus (thyme), Salvia (sage), Rosmarinus (rosemary), Monarda (bee balm), and Melissa (lemon balm). The rose family (Rosaceae) includes the genera Rosa (rose), Prunus (plum, almond, and cherry), Crataegus(hawthorn), Malus (apple), Rubus (raspberry and blackberry), Fragaria (strawberry), and many others.


The species is the most basic of all classifications. For example, Salvia officinalis (common garden sage) and S. sclarea (clary sage) are both highly aromatic plants, yet each has unique characteristics. In a publication, once the genus name has been established, it may be abbreviated thereafter in that same paragraph. When a species or species name is unspecified, it may be indicated with the abbreviation “sp.” For example, Salvia sp. indicates an unspecified species of sage. More than one species is indicated by the abbreviation “spp.”—for example, Salvia spp. refers to a group of Salvia species. These two abbreviations are not italicized.

Plant Subspecies and Varieties

A plant that differs genetically from some members of its species, but not enough to be classified as a species of its own, may be designated as a subspecies. Subspecies often result from interbreeding in geographically isolated populations. A subspecies is indicated by the abbreviation “ssp.” or “subsp.”

Plant subspecies can be further categorized into varieties. A variety, or variation in a species, is designated by the abbreviation “var.” followed by an italicized variety name, as in Achillea millefolium var. rubrum. This name indicates that the plant is a variety of common yarrow (Achillea millefolium) that has red (rubrum) flowers rather than white ones. Variety names are italicized; cultivar names are not.


The Work of the Angiosperm Phylogeny Group

Botanists now have advanced tools to help them understand the evolution of, and relationships among, plants. In the past, systematic botanists—those who study classification and evolutionary relationships between plants—depended mostly on characteristics from morphological studies (analyses of the form and external structure of a plant) as well as analysis of their different chemical compounds to produce classification systems. Today, modern molecular tools for studying the composition of DNA—deoxyribonucleic acid, which contains the genetic code essential to the development and functioning of all living organisms (except viruses)—have revolutionized botanists’ ability to classify plants. Now a botanist can classify a plant by the DNA sequence found in an individual species.

The process is similar to what’s used to help solve a crime or absolve the accused. This technology, along with new analytical approaches, has provided a wealth of information that can be analyzed using phylogenetics—the study of evolutionary relationships among organisms (in this case, plants). Perspectives obtained from phylogenetic analysis can be used to clarify and test plant classification systems and to further understand the plant kingdom and the groupings of its components.

Beginning in the late 1990s, a group of systematic botanists created the Angiosperm Phylogeny Group (APG) to produce a more precise classification system for flowering plants (angiosperms). APG retains some parts of the Linnaean system, plant orders and families, and requires that plants be grouped by their descendants from a common ancestor; this is known as the monophyletic approach. As a result, the placement of many families has changed. The term clade—a lineage—is used to group naturally related orders, families, genera, and species.

This work has led to the placement of some plant families within others, resulting in species that were formerly in one family now being recognized as part of another. Information on these new concepts can be found through an online search of “Angiosperm Phylogeny Group.”

Studying plants this way, at the molecular level, has truly revolutionized our ability to determine the relationships between and among species, genera, families, orders, and other groupings used to categorize plants—giving us a much greater understanding of plant classification. The closer scientists get to understanding how plants evolved and are related, the greater the ability of those who work on applied aspects of plant biology—including plant breeders, medicinal chemists, biofuel scientists, conservationists, and others who apply plant biology—to help feed, clothe, heal, fuel, and protect a growing world population and its environment.

For example, consider Taxol (paclitaxel), an extremely valuable plant-based medicine originally isolated from the endangered tree Taxus brevifolia. The quantity of bark needed for the production of a single therapeutic dose meant that there weren’t adequate supplies for patients’ needs; scientists eventually found compounds in a related, widely available Taxus species, allowing this vital medicine to be produced in the quantities needed. Having a precise understanding of plant relationships provided new insights into the search for biologically active molecules needed to make a drug in short supply. Far from an ivory tower exercise, obtaining an understanding of the evolution and relationships of plants, combined with an accurate classification system, greatly benefits us all.

Through DNA analysis, plant scientists have determined that chocolate (Theobroma cacao) belongs to the mallow family (Malvaceae), which also includes cola, cotton, and okra.

Although both of these plants are from the genus Salvia, Salvia officinalis (garden sage, left) and Salvia sclarea (clary sage, right) each have distinctive characteristics distinguishing them as separate species.

Cultivars and Hybrids

Unlike subspecies and varieties, cultivars do not occur naturally, but rather have been developed and perpetuated by cultivation. The term “cultivar” was coined from the words “cultivated” and “variety.” Cultivars can be hybrids created by breeding members of different species, or they may simply be desirable selections made from one species, chosen for a specific shape, flower color, aroma, or tolerance to certain environmental conditions. Cultivar names can be trademarked and registered with an International Cultivar Registration Authority according to specific nomenclature rules. Names of cultivars appear in single quotation marks after species names. Wandering through your local nursery, you might see a tree labeled Ginkgo biloba cv. ‘Autumn Gold’, indicating that this is a cultivated variety that someone has selected, named, and registered. Compared to the usual variant of the species, the cultivar ‘Autumn Gold’ has particularly beautiful golden leaves in fall and a more compact shape.

Hybrids occur when two different species cross (either in nature or by the hand of humans) to produce a new plant, usually with traits from both of the parents. They are denoted with an “×” between the genus and species names, as in Mentha × piperita, a cross between watermint (Mentha aquatica) and spearmint (Mentha spicata) that produces a plant known to all gardeners as peppermint.


Learning to identify herbs, understand their structure, and recognize them in their native habitats can open a new dimension of appreciation for plants and the natural world. In fact, many herbalists believe that developing a bond with a healing plant by admiring its beauty, learning to recognize it in the wild, or growing it in a garden is part of the benefit that plant has to offer.

On a basic level, flowering plants are classified by the number and arrangement of their flower parts, so understanding flowers is extremely important in plant identification. Biologically speaking, flower parts are the plant’s reproductive organs, so they’re essential to plant survival. The colors, fragrances, and shapes that make flowers irresistible to humans also, in many cases, function to lure pollinators to visit and pollinate the plant, thereby producing the seed that becomes the next generation of the species.

Leaves, too, are vital to a plant’s survival. One of the main functions of leaves is photosynthesis, the process that causes plants to transform sunlight, water, and carbon dioxide into food (sugars) and oxygen. Leaves also produce a vast variety of chemicals in highly specialized cells and glands. These chemicals perform functions vital for plant survival (not all of which are completely understood) and give plants their characteristic tastes, colors, aromas, and medicinal properties.


One of the best ways to learn to identify plants is to become familiar with the characteristics of whole plant families, not just individual plants. This is easier to do than it might sound and can streamline the entire process of plant identification.

The reason is simple: Plant families display patterns that remain consistent from species to species. For example, flowers in the mustard family have four petals in a crosslike pattern and six stamens. Pea family flowers have five petals: two wing petals, one banner petal, and two petals fused into what botanists call a keel. And lily family flowers have three petals, three sepals, and six stamens.

Developing the ability to recognize family characteristics and identify plants takes a bit of practice and perseverance. Begin by looking closely at plants to become adept at recognizing subtle similarities and differences among them. How many petals does each flower have? Do the flowers grow singly or in clumps on the stem? Are the leaves shiny or fuzzy? Are they oval or pointed, round or heart-shaped? Are their edges smooth or serrated? How are the leaves arranged on the stems? Does the plant live in a shady habitat near water, or is it found growing only in dry, sunny locations?

Choose a particular plant and observe its life cycle as it grows throughout the seasons. Learn what it looks like as a seedling and when it is flowering. Watch as the flowers mature and produce fruits and seeds, and examine the seeds. Finally, see what happens as winter approaches and the plant dies back or enters dormancy. By becoming intimately acquainted with a plant in this manner, it will always be recognizable, like the familiar face of a friend in a crowd. The following 10 plant families, each of which contains numerous herbs, are a good place to start.


Plant morphology includes vegetative structures (stem, leaf, and root) and reproductive structures (such as flowers and fruits).

Plant Families

These 10 plant families offer an opportunity to explore a variety of plant characteristics.

Apiaceae (carrot and parsley family)

Asteraceae (aster and sunflower family)

Boraginaceae (borage family)

Brassicaceae (mustard family)

Fabaceae (pea family)

Lamiaceae (mint family)

Liliaceae (lily family)

Ranunculaceae (buttercup family)

Rosaceae (rose family)

Scrophulariaceae (snapdragon family)

While learning to identify herbs, a local field guide is an invaluable resource. Another good tool is a magnifying glass, which is helpful for examining small flower parts. The best kind of magnifying glass for plant identification is a jeweler’s loupe with a magnification of at least 10x.

Nontechnical field guides are often organized according to flower color, which can be helpful for beginners. Technical field guides, or floras, are more challenging because they utilize what is known as a dichotomous key. It functions as a sort of flowchart that requires you to choose between two options at each point in the identification process, necessitating a working knowledge of botanical terms.

Botanists use a rich variety of highly specialized words to describe plant characteristics. Don’t feel overwhelmed by the prospect of learning all of these terms. Become familiar with some of the most common ones, and look up unfamiliar words. Nearly all plant identification books provide a glossary of essential terms.


For herb enthusiasts and gardeners, the most important categories of classifications to learn and understand are family, genus, species, and—when applicable—variety, cultivar, and hybrid. A good understanding of these will allow you to select, acquire, grow, and utilize the plants with the specific qualities you are seeking. Many people feel more comfortable using common names for plants simply because they are more familiar and easier to pronounce, and because plants can be purchased under those names from local nurseries and plant catalogs. If you feel intimidated by the thought of learning botanical names, consider that many common plant names—such as iris, crocus, chrysanthemum, and gladiolus, to name just a few—are actually scientific names that have been so widely used that they have become household words.


Biologically speaking, flower parts are all about reproduction. A flower’s showy, colorful petals are designed to attract pollinators such as insects, birds, and even bats. The grouping of petals together is called the corolla. Around the outside of the corolla are sepals, leaflike structures that enclose the flower before it opens. Sepals are often green, but they can also be so colorful that they are mistaken for petals. The grouping of sepals together is called the calyx.

Most flowers include both “male” (staminate) and “female” (pistillate) parts. The stamen, or male flower part, consists of a thin stalk called a filament, topped by an anther, the pollen-bearing structure of the flower. The pistil, or female flower part, is an upright structure in the center of the flower that consists of one or more styles, which are tubelike stalks. The style supports the stigma, the part of the pistil that receives the pollen. Once pollen is deposited on the stigma, it travels down the style to the ovary at the bottom of the pistil. The ovary contains a number of ovules that, when fertilized by pollen, develop into seeds.


A plant’s flowering structure can take many forms. Recognizing them is essential for proper plant identification.

Although most flowers have both male and female parts, single-sex plants are not uncommon. Technically known as dioecious plants, these bear male and female flower parts on separate plants, which means that both male and female plants must be present for pollination to occur. Dioecious herbs include ginkgo (Ginkgo biloba) and nettle (Urtica dioica). Single-sex flowers are called imperfect flowers; flowers that have both male and female parts are called perfect flowers.

In terms of plant identification, flowers are the most important part of a plant. When identifying a plant, begin by determining how many petals and sepals the flower has. Depending on the flower, this can be straightforward or tricky. Petals can be fused (joined together) or free. Flowers can be regular (symmetrical, with all petals the same size and shape, such as a mustard or rose family flower) or irregular (with some petals different from the others, as in a mint or pea flower). The color of the flower can provide some help, but flower color can be highly variable within a single species, making it an undependable characteristic for identification.


Plants in the daisy family (Asteraceae), including purple coneflower, have composite flowers; each is composed of hundreds of tiny flowers.

The aster family (Asteraceae) is one of the two largest flowering plant families. (The other is the orchid family, Orchidaceae.) The aster family’s daisylike flowers—called composite flowers—are unique in the plant world. Learning to recognize the basic characteristics of this kind of flower makes it easy to quickly rule out other possibilities when trying to identify a plant.

The sunflower, which is a typical composite flower, is not a single big flower but instead is made up of hundreds of tiny flowers; this is called a composite flower head. A typical composite flower head is composed of numerous ray and disk flowers. Ray flowers are longer, strap-shaped flowers that circle the edge of a flower head. Disk flowers are short, bristly flowers in the center of a flower head.


Learning the kinds of leaf complexity can help you identify the plant.

Sunflower plants have both ray and disk flowers, as do feverfew and echinacea plants. Some composite flower heads, however, are composed solely of either ray or disk flowers. For example, dandelion and chicory flower heads are made up of ray flowers only. Pineapple weed (Matricaria matricarioides), a close relative of German chamomile (M. recutita), has only disk flowers. The arrangement of flowers on a plant’s stem determines its type of inflorescence (flower cluster). This is another important identification feature. (See “Examples of Inflorescence Types.”)


Flowers play an essential role in reproduction. The color and fragrance of a flower attract pollinators, which play a vital part in a plant’s reproductive process. The color and fragrance also attract people, who in turn widen the plant’s distribution by planting it in other localities and even on other continents. Here are some useful terms to know about flower parts and related structures.


An elongated, central, supporting structure running through the leaf or stem


A collective term for the group of sepals (leaflike structures) that enclose a flower bud and encircle the petals when the flower is open


A collective term for petals


A short, broad, flat-topped flower cluster with individual flower stalks emerging at different points along an axis; the outermost flowers in a corymb open first


A short, broad flower cluster that always has a flower on the tip of the axis; in a cyme, the central flowers open first


The flowering part of a plant, usually used to denote a flower cluster or arrangement of flowers on an axis


An open flower cluster, sometimes pyramid shaped, with no terminal flower on the tip of the axis; a branched raceme


A stalk of one flower in a multiflowered inflorescence


A stalk of a solitary flower or inflorescence


The collective term for the corolla (petals) and calyx (sepals) together


A set of modified floral leaves, usually white or colored, that surround the stamens and pistils


The “female” organ of a flower, composed of three parts—ovary, style, and stigma


A simple, elongated stem with flowers on short stalks; flowers on the lowest part of the stem bloom first


A leaflike flower structure that encloses a flower bud and encircles the petals when a flower is open


A simple, elongated stem with stalkless flowers or flower heads; flowers on the lowest part of the stem bloom first


The “male” organ of the flower, composed of an anther containing pollen, most often on a filament


A cluster of flowers with stalks of almost equal length attached to a common point; individual flowers form a flat or nearly flat top


Leaves, although not as important as flowers in terms of classification, nonetheless provide essential clues for plant identification. When examining a plant, look at the way its leaves are arranged. The leaves can be opposite (arranged in pairs along the stem, as in plants of the mint family) or alternate (unpaired, occurring in an alternating pattern along the stem, as in plants of the borage family). Whorled leaves encircle a plant’s stem, a pattern that can be seen in many plants of the lily family. The leaves of some plants, such as mullein and plantain, form what is called a basal rosette—a cluster of leaves arranged in a circular pattern on the ground at the base of the flower stalk.

The structure of a leaf is an important element of plant identification. Leaves can be simple (consisting of only one part) or compound (composed of multiple parts, or leaflets). In the rose family, for example, five rounded leaf lets attached to a stalk make up a single compound leaf. Plants in the carrot and ginseng families also have compound leaves.

The leaflets of palmately compound leaves are all attached to the leaf’s petiole at one point. A pinnately compound leaf is composed of leaflets arranged on opposite sides of an axis. Even pinnate leaves have an even number of leaflets, odd pinnate leaves have an odd number.

After determining whether a plant’s leaves are compound or simple and how they are arranged on the plant’s stem, note the shape and texture of the leaves. Leaves can be glabrous (hairless) or pubescent (hairy); the edges (or margins) can be serrate (toothed) or entire (untoothed). And the leaves can be round, oval, heart-shaped, lancelike, or one of many other shapes.


An herb leaf’s shape and margins are defining characteristics associated with the plant’s genus and species.


Along with roots and stems, leaves are a basic organ of plants. Their primary function is photosynthesis: the process by which a leaf uses energy from sunlight to process water and carbon dioxide into carbohydrates, such as sugars, which the plant uses as food. The following terms are used to describe leaves, leaf shapes, and leaf structures.




At the base (as in a basal rosette of leaves); arising at the base of the stem


A reduced or modified leaf located close to the base of a flower or inflorescence

Compound leaf

A leaf having two or more distinct leaflets






Divided deeply into many narrow segments


Having the approximate shape of an ellipse


Leaf margins with no teeth or lobes


Lance-shaped, several times longer than wide; widest at the base and tapering toward the tip


Narrow and flat with parallel sides, like a blade of grass


A segment of a leaf, especially when rounded


The place on a stem from which leaves or branches originate


Somewhat rectangular; having greater length than width and a rounded, not squared, base and tip


Shaped like a hen’s egg, but having the wider end toward the tip


Similar to obovate, but with the wider section at the base of the leaf, where it is attached to the stem


With numerous leaf divisions radiating from one point at the base of the leaf


The stalk of a leaf blade or a compound leaf


Leaf divisions (leaflets) arranged along the axis or stalk


With sharp teeth, pointed forward


Having no stalk


A leaf with a blade in one piece, not compound; sometimes lobed


A modified leaf part, usually paired, found at the base of the petiole in certain plant families, such as the rose family


Leaves having three leaflets


A fruit is the fertilized, ripened ovary of a flower. It contains the plant’s seeds, fertilized ovules that hold the genetic material for a new plant. While some fruits are juicy, tasty structures such as apples, tomatoes, and plums, others are merely hard, dry seedpods.

Simple fruits ripen from an ovary with one pistil and can take many forms. Examples of dry simple fruits include an achene (buckwheat), a capsule (poppy), a caryopsis (grass), a cypsela (daisy), a follicle (milkweed), a legume (pea), a nut (acorn), a samara (elm), a schizocarp (parsley), and a silique (mustard plant). Examples of fleshy simple fruits include a berry (tomato), a drupe (plum), and a pome (apple).

Other classifications of fruits include multiple fruits (formed from a cluster of flowers, as in a pineapple), aggregate fruits (formed from single flowers with multiple pistils that are not fused together, as in a raspberry), and accessory fruits (not originating from an ovary but from tissue outside of the carpel, as in a strawberry). Fruits and seeds provide important foods and medicines and can be vital for plant identification.


A fruit and its seeds contain the genetic material for a new plant. These are a few of their many possible forms.


A plant’s stem offers structural support and serves as a transport and storage system for nutrients and water. Along the stem, nodes or swellings indicate where leaves, buds, or branches will arise. A stolon sprouts from the main stem and grows horizontally along the surface of the soil or just below the ground, referred to by gardeners as a runner. Stems can take many forms, both above and below the soil. A tuber such as a potato, for example, is actually a thickened underground stem, usually with numerous buds (eyes). Similarly, a rhizome, although often mistaken for a root, is actually an underground part of the main stem with roots attached. A bulb is a shortened stem covered by leaf bases or scales that enclose fleshy leaves.

Roots are underground structures that anchor and support a plant, absorb nutrients and water, and store food for the plant. Some plant roots are composed of a main axis with smaller roots coming off the primary root, known as secondary roots. Other plants, such as corn, have a fibrous root system that consists of many fine, threadlike roots. A taproot is a fleshy root that grows downward, sometimes swelling into a storage organ that is eaten, such as a beet or carrot. Roots of an individual plant can grow out several feet beyond the stem, thus competing for resources such as water and fertilizer. That’s why plant spacing, depending on the species grown, is important in the garden or farm field.


Roots provide structural support and absorb nutrients and water. Some also serve as a storage organ for the plant.


If you plan to collect plants from the wild, strong plant identification skills are essential. First, it is a matter of safety: You must be absolutely certain of the identity of the plants you gather, especially if you plan to use them for culinary or medicinal purposes. In the book Identifying and Harvesting Edible and Medicinal Plants in Wild (and Not So Wild) Places, noted forager “Wildman” Steve Brill cautions that if you are not 100 percent certain of the identity of a plant, do not eat it: “Look up all of a plant’s identifying characteristics, and make sure they match all your observations.” He also recommends looking up any descriptions of poisonous look-alikes and cross-checking multiple sources to be absolutely certain of the identification, palatability, and properties of a plant.

At The New York Botanical Garden, we often receive calls from local physicians, referred through a poison control center, about identifying plants that have been ingested or touched, in cases of possible poisoning or injury. Keep this number handy: 800-222-1222. It is the Poison Help Line number for the American Association of Poison Control Centers. These highly trained professionals can assist you in the case of a suspected poisoning—plant or otherwise. While most of the plant-related calls do not turn out to be life-threatening cases, others are—particularly those involving inexperienced mushroom foragers who mistake deadly species for those that are edible. There have also been cases of people poisoning themselves and their families after mistaking foxglove—a deadly poisonous plant—for comfrey. Others have died after harvesting the wrong member of the carrot family, which includes extremely poisonous plants, such as poison hemlock (Conium maculatum), in addition to wild medicinal herbs and edible varieties. Plants in the carrot family can be notoriously difficult to identify, even for experienced field botanists. While relatively few plants are as toxic as foxglove or water hemlock (Cicuta maculata), the wisest policy is not to taste or sample unknown plants.

Another important issue to consider when harvesting plants from the wild is conservation. As habitats dwindle, wild plant communities increasingly face pressure from the encroachment of human activities, such as development, deforestation, recreation, and, in some regions, commercial harvesting. As more people work to improve their health and well-being with herbal medicines, it’s also essential to protect the well-being of the planet and its life-sustaining plants. Before collecting any plants, learn which ones are rare or endangered in that area.


In the wild, plant identification can be a matter of life and death. Purple-stem angelica (Angelica atropurpurea; below left), which has been used for healing, could be confused with highly toxic water hemlock (Cicuta maculata; below right). Both have white flower umbels and hollow purple-tinged stems, and both grow in moist woodlands.

When gathering plants from the wild for any reason, be aware of good wild-harvesting practices, and obtain permission in advance if you wish to collect on any land, private or public, that is not your own. Knowing how to harvest plants sustain-ably and in ways that minimize damage to their habitats will ensure the survival of the individual plant community. Here are a few general rules.

• Never harvest rare herbs or plants of any kind. Some species are protected by law, and the penalties for harvesting them can be severe. Even if the plant being collected is not rare, never harvest when there are only a few specimens growing in one place.

• Do not harvest more plant material than needed. When a collector takes the root of a plant, the plant itself is destroyed. Harvesting bark harms trees, and removing a ring of bark from around a trunk can be fatal to a tree.

• Be sensitive to the surrounding vegetation. Don’t trample nearby plants in a burst of enthusiasm to collect a plant.

• Be cautious about potential pollutants that can contaminate the plants being gathered. Those collected near roadsides, for example, could contain unacceptably high levels of toxins, both from automobiles (lead and other heavy metals) and from chemical spraying. Plants gathered from streams could contain the same contaminants and microorganisms as do the waters, including bacteria such as E. coli.

In the end, the best course of action might simply be to grow medicinal plants or purchase herbs from a reputable supplier.

Whether you have taken a botany class at some point in your life or these concepts of plant identification are new to you, getting your arms around them will pave the way for greater enjoyment of the herbs you grow, collect, and purchase. When working in your garden, take the time to observe each plant. How does it differ from the ones alongside it? What are the shapes of its leaves? What type of inflorescence does it have? What does its root system look like?

If you are weeding, think about the difference between a weed and a useful plant. Certainly, plants considered weeds are not only in the “wrong” place, but they’re also aggressive. I can recall spending part of one beautiful spring weekend “weeding” a collection of mints I had purchased and planted the prior year—their stolons had spread throughout the garden like lava from a spewing volcano, and if not removed, they would have crowded out the other useful and ornamental plants struggling to grow there. The morphology and aggressive growth characteristics of certain mints make these species a weed in some cases and in other cases a most valued herb that can be harvested throughout the growing season.

Part of the great joy of spending time in the garden is observing its natural history—the interactions with pollinators, predators, soil, rain, and people—as well as the growth of each individual plant in your collection. Growing and using herbs in your daily life—strengthening that connection with your natural environment—can certainly help address the health condition that Richard Louv refers to as “nature-deficit disorder” in his wonderful book Last Child in the Woods.