The Age of Herbals

Throughout history, Europeans traveled the world searching for new trade goods and establishing better trade routes. Herbs and spices have been among the most valuable commodities, and the ancient Greeks and Romans were the first Europeans to seek them out. Since the seas were considered treacherous and unpredictable, the majority of trade with the Far East took place over land, until 40 CE, when a Greek merchant named Hippalus made a discovery about the monsoon patterns over the Indian Ocean.

The Age of Herbals

Hippalus realized that a ship leaving Egypt could reach India or the Indonesian Spice Islands faster by traveling with the prevailing southwesterly winds that blow in the summer months, and it could return more easily on the northeasterly winds of winter. Using this knowledge, a major expedition could be completed in just 1 year. The Romans took particular advantage of this insight, importing tons of pepper, cinnamon, cloves, and nutmeg and decreasing their reliance on the overland trade routes through Persia.

Few new trade routes were discovered until the 13th century, when Marco Polo (1254–1324) traveled from Venice through southwestern Asia, across the vast Gobi desert, and into Mongolia and China to be presented at the court of Kublai Khan. When he returned to Europe 24 years later, his travel journal sparked renewed interest in finding quicker, safer trade routes to the Far East. Many explorers followed over the next 200 years. On separate voyages, Bartolomeu Dias (1450–1500) and Vasco da Gama (1469–1524) navigated the Cape of Good Hope in Africa, opening a direct sea route from Europe to the East. Christopher Columbus (1451–1506) set out in search of a westerly route to the East Indies and discovered the herbal riches of the Americas, instead. Ferdinand Magellan (1480–1521) circumnavigated the globe and discovered the Philippine Islands, leading to the establishment of Manila as one of the world’s great spice trading capitals.

Advances in gardening and herbal knowledge in 16th-century Europe led to the publication of several new and interesting herbals. In earlier centuries, herbals for the common person were copied by hand from ancient Greek or Roman works, and repeated translations over the years caused many errors. But when printing presses came into use in the 1400s, authors could make more accurate plant descriptions and detailed illustrations available to the public, without the risk of adding errors with each printing. This helped renew interest in botany and the uses of herbs.

New Kreüterbuch (1543) and De Historia Stirpium (1545) by Leonhard Fuchs (1501–1566) of Germany were pioneering works in herbal publishing. The books contained more than 500 large, clear, woodcut prints of plant specimens with little or no text. As a doctor and professor of medicine, Fuchs felt compelled to create accurate depictions of medicinal herbs, having witnessed ignorance among the general public and even among his fellow physicians. Although his illustrations became extremely popular and were widely copied throughout Europe, Fuchs’s writing didn’t include anything new. Like most European authors before him, he simply rehashed the herbal remedies of Theophrastus and Dioscorides.

While Fuchs borrowed from the works of the ancient Romans, a charismatic Swiss physician and alchemist who called himself Philippus Aureolus Paracelsus (1493–1541) built on them. He traveled throughout Europe, Egypt, and the Middle East researching folk remedies and considered himself a practical man who spoke for the common people. He rejected Latin and wrote most of his books in German. He also rejected Galen’s theory of four humors, which had been practiced and mandated by the medical establishment for nearly 1,500 years.

Paracelsus was the first European to promote the idea of evidence-based medicine. He believed the active ingredient in each substance (animal, vegetable, or mineral) could be identified, extracted, and purified, and then prescribed in the correct dose to heal the sick. This approach led to the development of new herbal treatments—he dissolved opium in alcohol to produce laudanum, a highly effective painkiller—and to the debunking of current ones—he demonstrated that guaiac (Guaiacum officinale) imported from the West Indies was not an effective treatment for syphilis, as most Europeans believed, but that small doses of toxic mercury were very effective.


The Doctrine of Signatures maintains that a plant’s therapeutic value can be determined from its unique shape, color, aroma, and other characteristics. For instance, a plant with a thick, curled root would be useful for curing snakebite. Rauvolfia serpentina, also known as Indian snakeroot, was used in Ayurvedic medicine to treat snakebites (as well as other conditions) and eventually found its way into Western medicine as an early antihypertensive drug. According to the Doctrine, a plant with a yellow root or leaf might be useful to treat jaundice, associated with yellowing of the eyes and skin.

Exploring the Doctrine of Signatures in a 2008 article in Herbal-Gram, ethnobotanist Dr. Bradley Bennett wrote, “Some believe that the Creator gave physical clues about the value he imbued to plants. In 1669 Oswaldus Crollius wrote: ‘All herbs, flowers, trees and other things which proceed out of the Earth, are books, and magick signs, communicated to us, by the immense mercy of God, which signs are our medicine. . . . for every thing that is intrinsic, bears the external figure of its occult property . . . ’”

So many of the traditional cultures I have worked with—in habitats ranging from deserts to rainforests to high mountains—believe that many plants indicate their uses in this way. An inflorescence shaped like the stinger of a venomous insect can be used to treat the injury from that insect; plants with red leaves are good for treating the blood; and so forth. It really is impressive how ubiquitous this belief is and how well it was embedded in the most ancient of medical theories on the initial identification of plants with therapeutic properties.

But Dr. Bennett offers a more likely interpretation: This theory was not used to discover plants, but to explain and teach their therapeutic uses, as a mnemonic device to help retain and communicate this information to the vast audience of people interested in healing techniques and tools.

The Doctrine of Signatures

Paracelsus also believed that each and every plant was marked by God with a distinctive sign. This sign was both the key to unlocking the plant’s active ingredient and a clear indicator of God’s purpose for the plant. This theory was not entirely new, but it did take on new prominence in the world of herbalists when Jakob Böhme (1575–1624) codified it in Signatura Rerum (The Signature of All Things). This Doctrine of Signatures was extremely popular with the public because it made herbal remedies more identifiable and accessible. The spotted leaves of lungwort (Mertensia spp.), for example, were shaped vaguely like lungs, so clearly, the plant could be used to treat lung ailments. Goldenrod was yellow, so it must be an effective treatment for jaundice. Unfortunately, these simplistic “signatures” rarely corresponded with the actual medicinal values of their plants, and hundreds of new herbal myths grew without thorough scientific testing.