Tansy wasn’t just a pretty flower. An eighth-century emperor ordered every monastery in his realm to grow it.
Imagine a medieval household in the Rhineland, sometime around 900 CE. A woman is strewing dried herbs across the packed-earth floor — tansy, wormwood, pennyroyal, fleabane. The sharp, bitter scent rises as her feet crush the stems. She does this every week, has done it since she was old enough to carry a bundle, learned it from her mother, who learned it from hers, who learned it from hers — back and back and back through a chain of women whose beginning no one remembers.
She does not know the chemistry. She does not know that the thujone in her wormwood is a GABA receptor antagonist that disrupts insect nervous systems, or that the pulegone in her pennyroyal targets the same neural pathways that modern synthetic insecticides exploit. She knows only that it works. That the fleas retreat from the sharp-smelling floor. That the moths leave the wool alone. That her children sleep better on bedding stuffed with dried mugwort than on bare straw.
She is practicing a technology older than writing, older than bronze, older than farming itself.
THE CENTRAL EUROPEAN INSECT ARSENAL
Central Europe — the lands drained by the Danube, the Rhine, and the Elbe — has harboured a remarkable pharmacopoeia of insect-repellent plants since long before the last ice sheets retreated. These are not tropical exotics. They are common, weedy, persistent species that grow in disturbed ground, along paths, at woodland margins, and in the kind of open, nutrient-rich habitats that humans have always created around their camps and settlements.
The core arsenal includes six plants that anyone interested in prehistoric herbs and healing should know:
Wormwood (Artemisia absinthium): The queen of insect-repellent herbs. Intensely bitter, silver-leaved, and reeking of volatile oils. Used as a strewing herb, burned as fumigant smoke, and infused into oils for skin application. The Greek physician Dioscorides, writing in the first century CE, noted that wormwood “prevents clothes from being infested by moths and books from being eaten by mice” — and that was centuries after it had already been used for millennia.
Tansy (Tanacetum vulgare): Bright yellow button flowers on tall, ferny stems. So valued as an insect repellent that an eighth-century imperial decree — the Capitulare de villis, issued around 800 CE — mandated its cultivation on every royal estate across the Frankish empire. Tansy was placed between mattresses to deter lice and fleas, packed around stored meat to repel blowflies, and strewn on floors as a general household insecticide.
Common Fleabane (Pulicaria dysenterica): The name says everything. Burned as a fumigant, its smoke drove fleas from dwellings. A member of the Asteraceae family — the same family that includes the pyrethrum daisy, source of one of the most effective natural insecticides known to science.
Pennyroyal (Mentha pulegium): A low-growing mint with an unmistakable sharp, penetrating scent. Its very Latin name comes from pulex — the flea. Rubbed on skin as a direct repellent, strewn on floors, and placed in bedding. Effective but dangerous in concentration — pennyroyal oil is toxic to humans in large doses, a fact that speaks to the potency of its chemistry and the importance of the healer’s knowledge in dosing it correctly.
Mugwort (Artemisia vulgaris): Wormwood’s wilder cousin. Burned as smoke, hung in bundles around doorways and sleeping areas, and placed in bedding. Deeply embedded in European folk medicine — it appears in the Anglo-Saxon Nine Herbs Charm of the tenth century, where it is called “eldest of herbs” and credited with power against “loathsome things that rove through the land.”
Yarrow (Achillea millefolium): Named for the Greek hero who supposedly used it to treat battlefield wounds, yarrow is both a wound herb and an insect repellent. Hung in dried bundles, infused as a wash, or applied as a poultice for bite treatment. Its anti-inflammatory compound chamazulene soothes the swelling and itch of insect bites — making yarrow both shield and salve.
THE METHODS: STREWING, SMOKE, OIL, AND BEDDING
These plants were not used casually. The methods of application were specific, practical, and effective:
Strewing: Fresh or dried herbs scattered on floors, shelving, and storage areas. As people walked across them, the crushing released volatile oils that repelled crawling insects — fleas, ants, beetles. A strewn floor was not decoration. It was chemical warfare at ankle height.
Smoke: Dried herbs burned on hearth coals or in dedicated smudge fires. The smoke carried volatile insecticidal compounds into every corner of a dwelling, driving out flying and crawling insects alike. Archaeological evidence of hearth-side plant remains at prehistoric sites likely includes insect-repellent species, though proving deliberate selection (as opposed to accidental inclusion) remains challenging.
Infused oils: Herbs steeped in animal fat or plant oils created topical repellents. The oil base slowed the evaporation of volatile compounds, extending the effective period from minutes (for crushed fresh leaves) to hours. For any stone age healer woman, this knowledge — which fat, which plant, how long to steep, how much to apply — would have been core professional expertise.
Bedding: Perhaps the most critical application. Insecticidal leaves and stems layered into sleeping material protected the sleeper during the vulnerable, motionless hours of night. The earliest direct evidence for this practice comes from Sibudu Cave in South Africa, where 77,000-year-old bedding contained leaves of a tree whose chemical compounds have documented insecticidal and larvicidal properties. In Central Europe, the tradition of stuffing mattresses with mugwort, tansy, and wormwood persisted into the twentieth century in rural areas.
The more I followed the evidence, the more it began to feel like something else entirely — It was full of practical knowledge that is applicable even today. Despite the need to survive in a brutal landscape, it was free from the constant buzz of electronic devices and stressful dependence on corporate politics. It feels so peaceful in a way. That shift is what led me to write why the Stone Age keeps drawing me back.
THE CHEMISTRY BEHIND THE KNOWLEDGE
The effectiveness of these ancient remedies is not folk belief. It is measurable, reproducible chemistry.
Thujone — present in wormwood, tansy, and several other Artemisia species — is a GABA receptor antagonist. It interferes with the inhibitory neurotransmitter system in insects, causing hyperexcitation and death at sufficient doses. The same compound that makes absinthe dangerous in excess makes wormwood deadly to fleas.
Pulegone — the primary active compound in pennyroyal — disrupts insect nervous systems through a related but distinct mechanism. Its effectiveness against fleas gave the plant its name (Mentha pulegium, from pulex, the flea) and made it one of the most valued domestic herbs in pre-modern Europe.
The Asteraceae family, which includes fleabane, also includes the Dalmatian pyrethrum daisy — the source of pyrethrin, a compound so effective at killing insects that it became the basis for an entire class of modern synthetic insecticides (pyrethroids). Fleabane does not contain pyrethrin itself, but its related terpenoid compounds explain why burning it drives fleas from a room.
HOW FAR BACK DOES THE KNOWLEDGE GO?
Here is the question that haunts anyone who writes about the prehistoric world or reads fiction set in it: if these plants were growing in Central European landscapes throughout the Holocene — and they were — and if humans were living among them for ten thousand years before anyone wrote anything down — and they were — then how far back does the knowledge go?
We cannot prove that a Mesolithic healer woman in the Danube valley, six thousand years before the Common Era, deliberately selected mugwort for bedding or burned wormwood to clear her shelter of fleas. The plants decay. The knowledge leaves no archaeological trace. But we can say this:
The plants were there. The insects were there. The humans were there. And humans in southern Africa were using insecticidal plants in their bedding 77,000 years ago — long before modern humans even reached Europe. The behaviour is ancient. The available plants are effective. The pressure was constant. The inference is strong.
When you read prehistoric fiction and encounter a healer sorting herbs by firelight, choosing this leaf over that one, packing sleeping hides with fragrant stems — that is not romantic fantasy. It is the most reasonable reconstruction we can make of a practice that almost certainly extends back to the earliest human occupation of European landscapes.
TRY IT YOURSELF: THE ANCESTOR’S HERB BUNDLE
You can make a simple, effective insect-repellent bundle using plants that have been available in Central Europe since the Stone Age — and that grow easily in most temperate gardens or wild areas today.
Gather and dry: mugwort (Artemisia vulgaris), tansy (Tanacetum vulgare), and yarrow (Achillea millefolium). If you can find wormwood (Artemisia absinthium), add it. Tie them into loose bundles with natural twine and hang them near doorways, windows, and sleeping areas.
For a stronger effect, crush a few dried leaves onto a piece of tin foil and set them on a warm (not hot) surface — a sun-warmed rock, a radiator, a candle warmer — to release the volatile oils without open flame. The scent is sharp, herbal, and deeply ancient. It won’t eliminate every mosquito in a three-mile radius, but it genuinely does reduce insect activity in the immediate area, particularly indoors. For outdoor use, toss a handful of dried mugwort and wormwood onto campfire coals and sit in the drift of the smoke. You are now practicing the oldest insect-repellent technology known to our species.
Caution: Pennyroyal is highly effective but its essential oil is toxic to humans and pets in concentrated form. Use only the dried whole plant, never the concentrated oil, and do not use it around pregnant women, children, or animals. Tansy and wormwood should also be handled with care — effective as external repellents, they are toxic if consumed in quantity. These are powerful plants. The ancient healers knew their dangers as well as their gifts.
THE HERB GARDEN IS AN ECHO
If you grow tansy in your garden, you are tending a plant that an eighth-century emperor considered important enough to mandate by law. If you burn mugwort at your campsite, you are performing a ritual — not a mystical one, but a practical one — that connects you to the Mesolithic foragers who first learned that certain smokes drive the biting things away. If you hang yarrow bundles in your doorway, you are echoing a tradition that may be older than the last ice age.
The modern herb garden is not a novelty. It is an inheritance. Every bitter leaf, every sharp-scented stem, every yellow tansy button carries a message from the women who held the fire, who kept the knowledge, who understood that the war against biting things is never won — only managed, season by season, plant by plant, generation by generation.
The plants are still here. The insects are still here. And the knowledge, though it was never written down until recently, was never truly lost. It grew in the garden, waiting to be remembered.
