Mad Dog Skullcap: How This Herb Got Its Name
Most herbs are named for what they look like, where they grow, or what they were used for. Skullcap manages all three at once, and one of the names it picked up along the way is strange enough that people search for it on its own: mad dog skullcap.
It is not a warning. Nothing about the plant is dangerous to dogs, and it has nothing to do with how it behaves in a cup. The name is the residue of a medical episode from the 1770s that turned out to be wrong, and it stuck to the plant for two hundred and fifty years afterward.
We grow this plant in Charlevoix, and it is worth saying at the outset that it is native to Québec. Skullcap grows wild across most of North America, from Newfoundland and Québec west to British Columbia and south into California and Florida, generally in damp ground near marshes and wet meadows. When we put it in the field we are cultivating something that already belongs here.
The Rabies Cure That Was Not
In the 1770s an American physician began promoting skullcap as a treatment for hydrophobia, which is what rabies was called at the time. The usual name attached to the story is Van Derveer, sometimes written Vanderveer, an elderly doctor practising in New Jersey.
The claim spread quickly, which is not surprising. Rabies at the time was untreatable and uniformly fatal, and it would remain so until Pasteur's vaccine more than a century later. A country doctor offering a plant that could be gathered from a wet meadow was offering the only hope anyone had.
Period accounts describe the remedy being passed along by word of mouth well into the nineteenth century, and later retellings put impressive numbers on it, commonly a claim of several hundred people and a thousand head of cattle saved. Those figures circulate widely in herbal writing but do not appear in the contemporary reports, and the accounts disagree with one another on the details, including the year, which is variously given as 1772, 1773, or simply the 1770s. What is consistent across all of them is the outcome: the remedy did not work, the claim was never substantiated, and it was eventually abandoned.
What survived was the nickname. Mad dog weed, then mad dog skullcap, and it is still the name the plant is sold under in native-plant nurseries today.
Why Skullcap At All
The rest of the plant's names are more literal, and they are all describing the same small structure.
After the flower drops, the calyx that held it stays on the plant and develops a distinct little cap on its upper side. It is a few millimetres across and easy to miss until you know to look, at which point it becomes the fastest way to recognise anything in this genus.
The botanical name comes from that structure. Scutellaria is from the Latin scutella, a small dish or saucer, describing the shape of the persistent calyx. The common name comes from the same feature seen slightly differently, since the capped calyx is often described as resembling a small helmet.
The species name is doing its own descriptive work. Lateriflora means side-flowering, and it refers to the way the flowers are arranged: not in an upright spike at the top of the stem, as you see on hyssop or anise hyssop, but in loose one-sided rows running along the length of the stem from the leaf axils. That habit is why one of its other names is side-flowering skullcap, and it is the single most useful field character for telling it apart from its relatives.
It is also sold as blue skullcap, after the small blue-violet flowers.
American Skullcap and Chinese Skullcap Are Not the Same Herb
This is the distinction that matters most in practice, and it catches people out constantly.
American skullcap is Scutellaria lateriflora. It is native to North America, the part used is the aerial growth of leaf and flower harvested during bloom, and it is used as a relaxing nervine.
Chinese skullcap is Scutellaria baicalensis, also called Baikal or Baical skullcap. It is a different species from a different continent, the part used is the root, and it has an entirely separate history of traditional use.
The two share a genus and some overlapping flavonoids, but the compounds accumulate in different parts of the plant and in different proportions, and the two are not considered interchangeable. A product labelled simply "skullcap" has told you almost nothing. It is worth checking which species, and which part, is actually in the bottle.
The Germander Problem
The more serious identity issue in skullcap's history is not about the two Scutellaria species. It is about a plant from a different genus entirely.
Over the years a number of case reports linked commercial skullcap preparations to liver injury. The reports were real. What investigation eventually established is that the skullcap in question was not skullcap. It had been adulterated with germander, either Teucrium chamaedrys or Teucrium canadense, which are superficially similar in dried form and belong to the same family.
Germander carries a class of compounds called neoclerodane diterpenes. The specific structural feature that matters is an oxidised furan ring, and it is the oxidation of that ring that initiates the liver damage. Skullcap's own diterpenes do not have it. The clinical picture in the germander cases was consistent, including hepatocyte necrosis on biopsy and jaundice that resolved over a period of months once the preparation was stopped.
Analytical chemists have since worked out reliable ways to tell the two apart. Skullcap's phenolic profile is dominated by flavonoids, while the two Teucrium species are characterised by phenylethanoids, principally verbascoside and teucrioside. Under magnification the trichomes differ visibly as well.
The reason we think this history is worth telling rather than quietly leaving out is that it is the strongest possible argument for knowing where a herb came from. Adulteration is a supply-chain problem. It happens in long chains where dried plant material changes hands several times between the field and the bag, and it does not happen when one farm grows one species and puts it in a bag with its own name on it.
That said, the honest position is that this history explains the old liver warnings rather than erasing them. If you have a liver condition or take medication that affects the liver, the sensible thing is still to ask your practitioner first.
How to Recognise It
If you are trying to identify skullcap, whether in the field or in a bag, these are the characters that do the work:
- The flowers run along one side of the stem, in loose rows from the leaf axils, rather than standing in a terminal spike. This is the giveaway.
- The calyx keeps its little cap after the flower drops. Nothing else in a wet meadow looks quite like it.
- Square stems and opposite leaves, which places it in the mint family, though skullcap is not aromatic the way mint or lemon balm is. Crushing a leaf gives you very little.
- Leaves are toothed and taper to a point, on short stalks.
- It is a modest plant, usually somewhere between one and three feet, and it does not announce itself.
In dried garbled form the flowers and the capped calyces should still be visible in among the leaf. Material that is all crumbled leaf and stem fragments, with nothing recognisable in it, is material you cannot verify by eye.
How We Grow It
Skullcap is a wetland plant by preference, which is a thing to know if you are growing it deliberately, and a damp season can bring fungal pressure in a planted stand. We cut once a season, when the plants stand about eighteen inches and the flowers are opening along the stems, and then dry low and garble by hand so that what ends up in the bag is leaf and flower rather than stalk.
If you want the practical version of that, we have written up how to grow skullcap from seed separately. For what it tastes like and how to brew it, see our guide to skullcap tea.
Frequently Asked Questions
Why is it called mad dog skullcap?
Because it was promoted in the 1770s as a treatment for rabies, then called hydrophobia. The claim was never substantiated and the remedy was abandoned, but the nickname stayed with the plant.
Is mad dog skullcap dangerous to dogs?
No. The name refers to the historical attempt to treat rabies, not to any effect on animals.
Is mad dog skullcap the same as blue skullcap?
Yes. Mad dog skullcap, blue skullcap, and side-flowering skullcap are all common names for Scutellaria lateriflora.
What is the difference between American and Chinese skullcap?
They are different species used differently. American skullcap (Scutellaria lateriflora) uses the aerial parts. Chinese skullcap (Scutellaria baicalensis) uses the root and has a separate traditional application. They are not interchangeable.
Why does skullcap have a reputation for liver problems?
Historical case reports involved commercial skullcap adulterated with germander, a different plant containing hepatotoxic compounds that skullcap does not have. Standard caution still applies if you have a liver condition.
How do you identify skullcap in the field?
Look for flowers running along one side of the stem rather than in an upright spike, and for the small cap that persists on the calyx after the flower drops. Square stems and opposite toothed leaves place it in the mint family.
Where does skullcap grow wild?
Across most of North America, from Québec and Newfoundland west to British Columbia and south to California and Florida, typically in damp ground near marshes and wet meadows.
Want to learn more? Check out our other guides on skullcap:
- Skullcap Tea: Benefits, Taste, and How to Brew It
- How to Grow Skullcap From Seed
- Organic Skullcap — grown and garbled on our farm in Charlevoix
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