Ground Ivy, Glechoma hederacea
The bitter green world
Ground ivy, a.k.a. gill over the ground, creeping charlie, is just starting to begin its seasonal spread, all over gardens and lawns. Its genus, Glechoma, refers to it being a type of mint, and the species name means ivy-like, in recognition of the manner in which it takes over the landscape. Years ago, this weed was classified with catnip, sharing the genus Nepeta.
Glechoma hederacea is simultaneously a blessing and a curse. While the home owners’ associations and various farmers, gardeners and landscapers, from zone 3a to zone 10b, are trying to get rid of it, the Chinese have been using Glechomae herba, a dried product from this same species for numerous maladies, including kidney and gall stones, and have extracted a couple hundred compounds from it. This weed also has culinary utility as a bitter element to be added to salads, vinegars and teas, but not in such large quantity as other salad herbs, due to its medicinal potency.
Before this plant takes over your world this Spring, let’s make sure that you can identify it. If you take trouble to cultivate soil in your garden, this is the weed that comes back with a vengeance, since it spreads by seed and by roots that form on the nodes of the stems as it extends over the ground.
Ground ivy is one of the set of three easily confused weeds, along with last week’s purple dead nettle, and henbit. So, head back to Angelyn’s stellar post, which visually distinguishes them from each other. That, and the pics in this post, and last week’s post will help you out. (We’ll do henbit as soon as we find some.) As an official member of the mint family, Ground ivy has the square stem, and oppositely emerging leaves that you’ve come to expect. There are sparse tiny hairs on the fairly long leaf stalks (petioles) and on the leaves themselves. Leaves are almost round, (orbicular) with rounded (crenate) teeth on the margins. The leaf veins are palmate (like that of a maple leaf). Volatile oils are produced in visible little glands on the undersides of the leaves, the scent of which become apparent when the plants are chopped or crushed. A few weeks from now, sets of 3 bluish purple tubular flowers will emerge from the leaf axils. Some good floral pics are here and here, (while we wait for ours). At the base of the flowers is a hairy green calyx made with 5 visible teeth/petals. The flower itself has 4 or 5 petals, and opens up, trumpet like. At the opening, the larger lower lobe, where insects land, is notched, as is the smaller, upper lobe, and a lobe projects from each side. Inside the flower are 1 pistil, 2 long stamens and 2 short stamens, as well as a number of of hairs. From each flower, pods bearing 4 nutlets (seeds) are produced.
In zone 6, small ground ivy plants can be found hugging the dirt through much of the winter, and they take off growing as soon as the days warm up. By mid spring they will be flowering. This is the time that most herbalists choose to harvest the plants for medicinal use, though studies show that much of their constituents are available even before flowering. The palatability of the leaves is better when the plants are young, as a bitter additive to salads. Think of this herb as more of an additive or topping rather than the entire salad, as it is more strongly medicinal than the last 3 plants which we covered. It has a minty strong bitter taste which could spice up a recipe when mixed in. If horses heavily graze this weed, it will make them sick.
Ancient herbal literature extolls the medicinal use of ground ivy, going all the way back to the years of Dioscorides, who is said to have recommended long term use of an infusion for sciatica, and Galen, who used it externally for eye inflammations. Industrial usage included brewing, in order to clarify, impart flavor, and preserve ales, prior to the discovery of hops for such purposes. John Gerard’s 16th century Herball touts the use of ground ivy for tinnitus and the hard of hearing. He and William Salmon (1710) recommended that the juice be placed in the affected ears. Henrietta Kress, owner of the oldest, largest online, herbal compendium, points to the use of ground ivy tea, 2-3 cups per day, until the ringing is gone. That’s the world of herbalism :-)
Like most of the medicinal plants, controlled human trials, of the kind that drug companies pay for, are pretty much non-existent. That this plant had so many ancient uses points to the veritable punchbowl of lignans, alcohols, anthraquinones, terpenes, organic acids and esters, volatile oils, flavonoids and their glycosides, and other substances within it.
One of the trendy uses for glechoma is in recipes for digestive bitters. The strong taste stimulates bitter taste receptors, T2Rs, which are found not only in the mouth, but all along the digestive system, the pancreas, in blood vessels and heart tissue. When stimulated, these receptors initially stimulate the appetite, salivation and secretion of digestive juices, and perhaps blood flow to the digestive tract and other organs. Later the bitters stimulate the upper and lower sphincters of the stomach to close, allowing more complete processing of the food, and a feeling of fullness. Closure of the upper “cardiac” sphincter of the stomach, stimulated both by “enough” stomach acid, and those bitter taste receptors, prevents gastro-esophageal reflux. Digestive bitters play a role in preventing over-eating, and helping to control blood sugar. Bitter taste receptors also line the airways and lungs, and are believed to modulate immune response to infection. This might form part of the basis for the traditional use of Glechoma hederacea for chronic lung conditions and cough, along with the presence of anti-inflammatory compounds and eucalyptol. As a practical matter, digestive bitters work the best when you eat them directly. Bitter herbs can be combined for additive effects. You need to “taste the rainbow”, to get the digestive juices flowing before dinner. Secondarily, you could taste the tea or alcoholic tincture. This plant is directly available for most of the year, so we just eat it :-)
Glechoma hederacea is implicated in various herbal literature sources for its pulegone content. That has become a considerable bogey-man chemical due to its hepatotoxicity and carcinogenicity. Tiny amounts of pulegone are present in many members of the mint family which are commonly eaten as spices and flavorings. This is why we have to be sure that everyone knows the dose difference between herbs and essential oils. The dried form of ground ivy contains about 0.09 percent essential oils. Concentrating this one thousandth portion of the herb produced only trace amounts of pulegone among hundreds of volatile oils identified in this plant. Eucalyptol and germacrene D and figured prominently among this collection, but by no means comprise the majority of it. This little weed is the dumpster of phytochemistry. “Darwin awards” have tragically been bestowed upon people who internally used the essential oil of pennyroyal, the majority of which is pulegone. This constitutes a massive overdose, and really doesn’t have a practical relationship to the use of the whole pennyroyal herb, nor especially to the use of ground ivy, which contains a vanishingly small quantity of pulegone.
We urge people to avoid the internal use of undiluted essential oils in general. Think of it in the same way as those designer street drugs, which are fatal in milligram doses. Essential oils must be highly diluted for internal use, and taken in tiny doses. Dilution is also strongly advised for external use.
Much of research justifying the use of glechoma hederacea is being done in Asia. Since it has had a strong role in traditional medicine, they’re trying to discover why it works.
Back in the days when ground ivy was used in beer, a prominent diuretic effect was noted, which was likely additive to the alcohol itself. This effect might be contributing to the effectiveness in preventing or treating stones in the kidneys and urinary tract. Chinese were using the herb to treat stones in domestic animals, and controlled experiments showed it to be effective in preventing and treating kidney stones in rats. Proposed mechanisms were urinary acidification, to help dissolve stones, calcium uptake by flavonoids and organic acids, to prevent stone formation, and the general flushing effect of diuresis caused by the herb. Most significant on the home medicine front is that this benefit of the herb is extractable by water, ……. so it’s tea time.
Did you ever wonder what to do when the little herb book tells you that an herb is both a laxative, and good for treating diarrhea? (We’re not talking fiber, here.) Herbs, especially this one, contain a lot of different molecules, and that’s why it’s important to delve deeper. The water extract of ground ivy tends to excite smooth muscle per guinea pig experiments, leading to a laxative effect, while the alcohol extract of this herb has been shown to inhibit motility of the smooth muscle, thereby slowing the intestinal transit time. This indicates that the tea is more applicable for constipation, and the ethanolic tincture is more applicable for slowing down the squirts of diarrhea. Teas and tinctures of a given herb are not equal.
Some of the herbal constituents are available in both the water and ethanol extracts, and this is apparently the case for those which act as cholegogues. Both of these extracts were demonstrated in rats to increase bile production, increase bile acids, and decrease the formation of gall stones, at equivalent doses. Other experiments in guinea pigs showed a reduction in cholesterol present in the bile, and an increase in lecithin.
Experiments in mice have shown that ground ivy extract can reduce blood sugar in those with streptozocin induced diabetes, (hyperglycemia), but not in the animals with normal blood sugar.
Numerous anti-cancer compounds have been identified among the constituents of ground ivy, including ursinic acid, rosmarinic acid, euscaphic acid, β-elemene, quercetin, oleanolic acid, and apigenin. These operate by various mechanisms ranging from direct action to kill tumor cells, to enhancement of immune function to naturally fight cancer.
This is merely a cursory search through the amazing molecular cornucopia of ground ivy, as we encourage you to know and love your weeds. We have not yet addressed the numerous phenolic and volatile constituents with antimicrobial properties. As time goes on, we will delve deeper into the practical utility of each weed, inspiring you to let them all grow wild and drive the neighbors mad.
Comments? What’s your favorite spring weed? Maybe we should cover it next!
Where we Dig
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