Plant Confusions: the Bugleweeds, Ajuga and Lycopus

Growing in my back yard since I bought the house in 2006 is a plant I only just learned a name for. Its Ajuga reptans, a little mint native to Europe that is used as a ground cover. My friend called it ajuga, and ajuga is used as its common name. Reading about it, I discovered the common name in USDA plant list (link) is bugle. Googling it sends you to bugleweed. 

bugleweed, Ajuga repens

Knowing it as ground cover, I was surprised to find it mentioned as a medicinal plant. 

But searching for more information on its medicinal qualities, I found I was often reading about Lycopus. For example, when I followed "bugleweed for thyroidism" I arrived at an article for Lycopus virginicus.

Lycopus is another mint genus, taller than Ajuga, with some plants native to North America. 

Here's the distinction: 

Ajuga is a genus of some 40 plants (or 300, depending on your source) native to Europe, Asia, Africa and Australia but not the Americas. They tend to be low and spreading with colorful leaves. Five species have been introduced to North America and have escaped at least enough to be listed in the USDA plants data base. Americans call them bugleweed, carpet weed, bugleherb, bugle, carpenter's weed, and St. Lawrence weed. 

bugleweed, Ajuga repens

Lycopus is a genus of about 20 species, native to Europe, Asia, Australia and North America. Common names for Lycopus species include bugleweed, gypsywort, and water horehound.

bugleweed, Lycopus europaeus

Both Ajuga and Lycopus are in the mint family, Lamiaceae, so they have square stems and mint-like pale, blue or purplish flowers. (I don't have a photo of Lycopus flowering: google Lycopus flower. link) Within the mints, though, they are in different subfamilies, not very closely related among the 236 genera in the Lamiaceae. Both have been used medicinally, but not for the same conditions. 

They are certainly not the same plant species. 

Looking at the two genera in European sources, I got more common names. Grieve writing in the 1930s in England, says common names for Ajuga are common bugle, carpenter's herb, sicklewort and middle comfrey (A. reptans), and yellow bugle and European ground pine for Ajuga chamaepitys, the one Europeans used the most medicinally. She gives the common names water bugle, sweet bugle, Virginia bugle, Virginia water horehound, and gipsyweed for Lycopus virginicus, a New World species, and water horehound, gipsy-wort and Egyptian's herb for Lycopus europaeus, from Europe. The uses Grieve gives for Ajuga include for stopping hemorrhaging and the coughing of blood, and problems of bile and gall bladder. In lard, Ajuga was used to treat bruises, sores and skin ulcers. The uses she gives for Lycopus it are chiefly as a black dye.

Ajuga bugleweed

Over the past 500 years, the two plants have switched places as herbal medicines. Lycopus was studied by German Commission E and found to be an effective medicine treating mild hyperthroid disorders, so is a validated herbal medicine. Ajuga does not occur in 21st century herbal medicine references and has not been studied by German Commission E. There are publications on Ajuga species that find active ingredients in the plant and report folk medicine uses, but these are from central Asia and India, and feature species of Ajuga not found in the United States. 

Lycopus bugleweed

It is not clear to me why both plants are called bugleweed in North America. But they are and a substantial number of people writing on the internet didn't notice there are two different plant genera. 

For example:"Bugle weed is the common name given to at least two low-growing flowering ground cover plants which are members of the Ajuga family, Lycopus europaens and Lycopus virginicus. Ajugas are part of the Lamiaceae, the same grouping to which plants of the mint family belong...Bugle weeds usually have shining, ovalshaped leaves that are reminiscent of spinach leaves in appearance..." The plant with shiny leaves is Ajuga, not Lycopus. The medical advice is likewise mixed up, jumping back and forth between species. (This is from encyclopedia.com link and they are quoting a printed herbal work, Gale Encyclopedia of Alternative Medicine, but, nevertheless, it is wrong and should be corrected. They did not respond to my inquiry.)

They are not alone. WebMD lists the plant as bugleweed and gives ajuga as the first of the "other names" 

" OTHER NAME(S): Ajuga, Archangle, Ashangee, Chanvre d'Eau, Green Wolf's Foot, Gypsy Weed, Gypsywort, Hoarhound, Lycope, Lycope d'Amérique, Lycope d'Europe, Lycope de Virginie, Lycopi Herba, Lycopus americanus, Lycopus europaeus, Lycopus Europea, Lycopus virginicus, Menta de Lobo, Patte-de-Loup, Paul's Betony, Sweet Bugle, Water Bugle, Water Hoarhound, Water Horehound, Virginia Water Horehound, Wolfstrapp." link 

Most of these are common names for Lycopus europaeus and L. virginicus, but Ajuga is emphatically not. The list was clearly cut and pasted from some obscure old source; I find other plants but not Lycopus called archangel and gypsy weed, a confusion which could be dangerous since this is a medical site. (Again, I contacted them. They replied they had forwarded my inquiry to the vendor they use for their drug data base. They said it takes a quarter of a year and it has only been 6 weeks, but so far it has not been updated.)

So, beware online confusions of these two plants. 

Note that, if the source says Native Americans used the bugleweed, they are talking about Lycopus virginicus (or a less common American species of Lycopus) because Lycopus europaeus and the ajugas are Eurasian and not widespread in North America. The German Commission E study endorsed both Lycopus europaeus and L. viriginicus for hyperthyroid treatment.

Lycopus bugleweed

Ajuga bugleweed

In summary: bugleweed is the common name of two different plants. Ajuga is a common ground cover. Lycopus is used in herbal medicine. Don't mix them up.

Comments and corrections welcome

References

Encyclopedia.com. Bugle Weed.  link (Accessed 9/1/22)

Grieve, M. 1931. A Modern Herbal. Dover, New York. Online: 

Gruenwald, J., T. Brendler and C. Jaenicke, editors. 2007. PDR (Physician's Desk Reference) for Herbal Medicines. 4th ed. Thomson Publishing, Montvale, NJ. 

Web MD Bugleweed. link (Accessed 9/1/22)

Kathy Keeler, A Wandering Botanist
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