Squirrels Love Medicinal Dandelion Roots

A tree squirrel family territory crisscrosses my backyard. The squirrels have a hearty appetite and sample almost everything, consistently avoiding only a few highly aromatic mint family plants. The tall fescue backyard turf is now mostly remnants, having been grazed down by rabbits, packs of dawn-grazing mice, underground grubs and heaven knows what else. All made worse by gardeners from Mexico who trampled and compacted the soil 50 weeks a year for several years with heavy boots and leaf blowers that acted like hair dryers and sealed the soil surface so tightly shut that it was impermeable to water and on its way to resembling their northern Mexico desert homeland. I welcomed the tall weedy dandelions springing up in the bare spots, as I knew their deep taproots would break up the hard soil, which I had sprinkled with commercial potting compost and leaves to hasten soil rebuilding. Dandelion roots create channels for soil air and water movement, and dandelion leaves are repositories for deeper deposits of nutrient minerals brought nearer the soil surface.

That squirrels were munching on dandelion leaves was no big surprise, as some dandelion cultivars are considered salad or cooking greens or associated with traditional medical remedies. Then I started seeing empty holes in the ground where dandelions had once stood tall, as if someone was secretly sneaking in and weeding out the dandelions. But there were no gophers or ground squirrels around, and the compulsive weed haters in the neighborhood favored herbicides over hand-weeding and digging. One day I noticed a squirrel digging in the ground and uprooting a tall dandelion, which it lifted into the air and ate from the bottom of the long taproot to the top with a facial expression of obvious delight. Soon all the dandelion plants were gone, consumed in a frenzied squirrel feast. But new dandelions emerged elsewhere with rosettes of leaves flat to the ground and harder to chew; though the squirrels eventually got those, too. Thus, dandelions lead a tough life, with no means to run from hungry squirrels; and 95% of their fluffy seeds that blow in the wind feed an ecological food chain of seed-loving ground beetles, birds, fungi, soil-dwelling isopods, etc.

But what is it about dandelion roots that squirrels so love, I wondered? Are dandelion roots just tasty and nutritious, or is there more to the story that people have overlooked in their blind zeal to eradicate what they consider a weed? The common dandelion goes by the scientific name, Taraxacum officinale. However, the genus Taraxacum contains about 2,500 dandelion species, only a few of which have received research attention as medicines, anti-cancer drugs, human and animal foods, natural rubber and industrial latex sources, etc.

The term “officinale” in the scientific name for dandelion “literally means belonging to an officina, which in the past indicated the storeroom of a monastery, where medicines and other necessaries were kept,” write Laura Grauso, Giuliano Bonanomi and colleagues in Naples, Italy (Phytochem Rev (2019) 18:1115-1132). “Thus, this species name is given to plants that possess medicinal, culinary, or other uses.” In medieval Europe, before monarchs like England’s Henry VIII and “people’s revolutions” like the French Revolution (Reign of Terror) “confiscated” (nationalized) and “redistributed” their lands, monasteries operated vast agricultural estates accumulated (via donations, bequests, etc.) over many centuries. Monasteries grew and processed herbal medicines, breads and grains, dairy cheeses, wines and beverages, honey and beeswax candles, linen clothing, etc.; which were kept in storerooms or officinas for monastery use and ministering to suffering and poor people seeking help. In today’s modern Western world, warfare-welfare states have taken over the monastery’s charitable functions; and funding now comes from state taxation at rates far exceeding the 10% religious tithe. The scientific term “officinale” is one of the few remnants of the older system, where religious orders doing their duty to help a suffering humanity provided welfare to the poor while monks formulated and ministered medicinal herbs such as dandelion.

Dandelion roots, like those eaten by the squirrels, “have a bitter and turnip-like flavor,” and “if collected from 2-year-old plants, they can be roasted to prepare a coffee substitute,” note the Italian researchers. “Leaves are also quite bitter and that’s why they are often blanched before consuming.” Dandelion wine is brewed from flower petals, sugar and often lemon juice. Since medieval times in Great Britain, dandelion and burdock have been brewed as a carbonated drink.

“With the improvement of health awareness, in recent years, dandelion has gradually become a new trend as a medicinal and edible vegetable in China,” wrote Zhe Wu, Xuelin Lu and other researchers at the Institute of Coastal Agriculture in Tangshan, China (Folia Hort. 31(2) (2019): 277-284). Besides being “a widespread weed” with “strong resistance to environmental adversities,” dandelion leads a double-life as “a traditional Chinese herbal medicine which is rich in polysaccharides, phenolic acids, sterols and other substances, and has sterilization, anti-inflammatory, anti-oxidation and immunity enhancement functions.” Methods for commercial growth and harvest of dandelion roots for medicines and natural rubber on otherwise barren lands are being studied in China’s Hebei province. The idea is to make use of abandoned saline-alkaline land where “the soil is mainly composed of muddy saline-silt with a high salt content of even more than 1.2%, which, coupled with less rainfall, leads to a large area of barren land.” In other words, take advantage of the weed’s natural proclivities and harvest it as a crop from abandoned lands otherwise unsuitable for plant growth.

“Plants of the genus Taraxacum, commonly known as dandelions, have a history of use in Chinese, Arabian and Native American traditional medicine, to treat a variety of diseases,” and “play a pivotal role in traditional Chinese medicine (TCM) and are frequently used for treatment of breast, uterine and lung tumors as well as hepatitis and digestive diseases,” write Sophia Sigstedt, Wim Steelant and colleagues in New Mexico, USA (International Journal of Oncology 32: 1085-1090, 2008). “The variety of health benefits associated with the use of dandelions has been attributed to specific Taraxacum species.” A few examples: Aqueous root extracts of a Japanese dandelion, Taraxacum japonicum, contain two triterpenoids, taraxasterol and taraxerol, which are effective against skin tumors in mice and inhibit “spontaneous mammary carcinogenesis after oral administration.” Ethanol extracts from roots of a Chinese dandelion, Taraxacum mongolicum, inhibit mouse melanoma cells. Water extracts of common dandelion, Taraxacum officinale, also demonstrate antitumor activity.

“Medicinal plants, originating from or related to TCM (traditional Chinese medicine), play an important role in the treatment of cancer and represent a valuable source for the discovery of small molecule inhibitors targeting signal transduction proteins, e.g. kinases, that modulate proliferation and invasion of cancer cells” write the New Mexico researchers. But “the exact reason for the reduction in invasion cannot be explained at present, as many of the known components in the roots and leaves can contribute to the observed effect.” Mostly, this just scratches the surface of dandelion extract anti-cancer potential, as relatively few compounds among several hundred have been isolated and experimentally tested alone or in combination in a dose-response fashion.

In the journal Evidence-Based Complementary and Alternative Medicine (Vol 2019, Article ID 2951428), Christopher Nguyen, Siyaram Pandey and University of Windsor colleagues in Ontario, Canada provide experimental evidence that oral doses of dandelion (Taraxacum officinale) and lemongrass (Cymbopogon citratus) extracts enhance cell death (apoptosis) induction against prostate cancer; and are compatible with reduced doses of standard drugs such as taxol and mitoxantrone. The herbal extracts were “well tolerated” in mice, “as indicated by normal weight gain and food intake.”

Besides enhancing conventional cancer drug efficacy and reducing deleterious side effects, these dandelion and herbal extracts could “improve the quality of life due to reduced toxicity for prostate cancer patients.” In a USA human clinical test with “an aggressive and generally resistant cancer,” chronic myelomonocytic leukemia (CMML), “hematological parameters remained stable” and “bone marrow blast counts vastly improved while taking papaya leaf extract and dandelion root extract,” noted USA researchers Leena Rahmat and Lloyd Damon (Case Reports in Hematology, Vol 2018, Article ID 7267920).

In traditional Chinese medicine (TCM), dandelion extracts have “played a significant role in fighting” annual pandemics of RNA viruses such as influenza A and B and Avian or bird flu. “The lag time between virus identification and vaccine distribution exceeds 6 months and concerns regarding vaccine safety are a growing issue leading to vaccination refusal,” wrote Chinese Academy of Sciences researchers Wen He, Huamin Han, Wei Wang and Bin Gao in 2011 (Virology Journal 2011, 8:538). Drugs have not been very effective, and RNA viruses rapidly develop resistance. However, dandelions are potent inhibitors of influenza virus infections in cell cultures via “inhibition of viral polymerase activity and the reduction of the virus nucleoprotein (NP) RNA level.”

Perhaps more importantly, dandelions are also high in polyphenol compounds effective against RNA viruses and many other pathogens via a physical mechanism. “Polyphenols have protein-binding capabilities, which suggests that components of dandelion extracts may interact with pathogens through physical, non-specific interactions,” wrote Han, Wang and Gao. “Two potential advantages of this non-specific mechanism of action may be that resistant variants only emerge rarely and that dandelion extracts may also act against bacterial co-infections that represent a major complication in severe influenza virus infections.” Research using TCM and dandelion extracts in COVID-19 treatment is underway.

“Dandelion is composed of multiple compounds that are able to regulate multiple targets for a range of medical indications and that are able to be titrated to the specific symptoms of an individual,” note the Chinese Academy of Sciences researchers. “Dandelion is a natural diuretic that increases urine production by promoting the excretion of salts and water from the kidney. Dandelion extracts may be used for a wide range of conditions requiring mild diuretic treatment, such as poor digestion, liver disorders, and high blood pressure. Dandelion is also a source of potassium, a nutrient often lost through the use of other natural and synthetic diuretics. Additionally, fresh or dried dandelion herb is used as a mild appetite stimulant and to improve stomach symptoms, including feelings of fullness, flatulence, and constipation. The root of the dandelion plant is believed to have mild laxative effects and is often used to improve digestion.”

Animals such as broiler chickens, plagued by outbreaks of diseases such as Avian or bird flu, can be farm-reared with dandelions or dandelion fermented probiotics as an alternative to antibiotic drugs such as chlortetracycline, suggest South Korean researchers J.I. Oh, G.M. Kim, S.Y. Ko, I.H. Bae, S.S. Lee and C.J. Yang at Sunchon National University. The Korean dandelion, Taraxacum coreanum, and dandelion fermented probiotics were evaluated in controlled and replicated randomized experiments measuring broiler chicken growth and meat quality. Oleic acid content, important to taste and meat quality, was significantly increased (compared to the control) by 0.5% dandelion fermented probiotics. Besides better chicken taste and meat quality, lower blood cholesterol was another dandelion advantage.

Besides being good chicken feed, some dandelion species also have industrial utility as an alternative source of natural rubber; and this can help save rain forests. “Natural rubber is a strategic raw material essential to the manufacture of 50,000 different rubber and latex products” in “the industrial, consumer, medical, and military sectors,” writes Katrina Cornish of the USA’s Ohio Agricultural Research Center (Technology and Innovation, Vol. 18, pp. 245-256, 2017). “World natural rubber consumption is expected to be 16.5 metric tons/year by 2023 and to continue to increase thereafter and lead to “global natural rubber shortages.”

Natural rubber has high-performance qualities not found in synthetic rubbers, currently manufactured from fossil-fuel feedstocks. Natural rubber advantages include: “high elasticity, high resilience, dynamic performance, high tensile strength, good wear resistance, low electrical conductivity, and excellent heat dispersion,” notes Cornish. “Natural rubber properties become progressively more important in tire manufacturing the higher the tire performance required. For example, the rubber component of airplane tires is entirely composed of natural rubber. Compared to natural rubber, synthetic rubbers are more resistant to oil, certain chemicals, and oxygen; have better aging and weathering characteristics; and demonstrate better resilience over a wider temperature range.”

Expanding cultivation of Taraxacum kok-saghyz, also known as rubber root or Russian dandelion (native to Kazakhstan, Uzbekistan, northwestern China) can help meet the growing world need for natural rubber and latex. And at the same time reduce the need to clear Amazon rain forests for plantations of Brazilian rubber trees, Hevea brasiliensis.

Besides Brazilian rain-forest rubber trees and Russian dandelion roots, a slightly different high-quality rubber and latex can be obtained from guayule shrubs (Parthenium argentatum) native to northern Mexico’s Chihuahuan desert. Guayule grows well on non-agricultural lands, like in the USA’s Arizona deserts. Guayule latex lacks the allergens of the other natural rubbers, a major advantage; and has found high-end niche markets like high-altitude weather balloons, lineman’s gloves and condoms. But unlike rubber tree rubber, guayule and dandelion rubber currently lack the economies of scale needed to be widely-used as commodity products. “However, it may be possible to interest manufacturers of high-margin products (e.g., shoes, sports equipment, etc.) in premium-priced, ‘Made in America,’ sustainable Taraxacum kok-saghyz rubber because, unlike tires, such products can absorb large price differentials in their raw materials,” notes Cornish.

My thanks to the squirrels whose love of dandelion roots stimulated interest in this topic.

Pollinator-Friendly Lawns: Flowers or No Flowers?

TURF is a $25 BILLION USA INDUSTRY, said Nastaran Tofangsazi of the University of Florida (Apopka, FL), a sex pheromone researcher looking to complement biocontrols like beneficial Beauveria bassiana fungi and Steinernema carpocapsae nematodes to control the browning and uneven grass growth caused by tropical sod webworm (Herpetogramma phaeopteralis) in Florida’s $9 billion worth of turfgrass. Also at the Entomological Society of America (ESA) annual meeting, Auburn University’s R. Murphey Coy noted that the USA’s 164,000 km2 (63,320 square miles) of turf is the USA’s most irrigated crop. Turfgrass irrigation consumes 300% more water than corn; plus 4.5 pounds (2 kg) of nitrogen per 1,000 square feet (93 m2).

Alabama is among the top USA turfgrass-producing states, and Auburn University researchers are looking to reduce turfgrass water, nitrogen and iron inputs by colonizing grass seeds and roots with easy to apply sprays of plant growth promoting rhizobacteria (PGPR). Blends of PGPR species such as Bacillus firmis, Pseudomonas and Rhizobium in turfgrass and cotton induce systemic resistance to pestiferous Fusarium fungi and triple parasitic wasp biocontrol of the caterpillar larvae of moth pests like fall armyworm (Spodoptera frugiperda).

Not everyone is a fan of turfgrass lawns, and before the modern chemical era lawns were more like fragrant flowery meadows. “Agricultural experts and agribusiness are bound by the idea that even land that has lost its natural vitality can still produce crops with the addition of petroleum energy, agricultural chemicals, and water…considering this form of agriculture to be advanced,” wrote Japanese agriculturist and philosopher Masanobu Fukuoka in the book, Sowing Seeds in the Desert (edited by Larry Korn).

“When I suggested that it would be a good idea to plant fruit trees to line the streets in towns and cities and to grow vegetables instead of lawns and annual flowers, so that when the townspeople were taking a walk, they could pick and eat the fruit from the roadside, people were surprisingly enthusiastic,” said Fukuoka. “When I suggested that it would be good to scatter the seeds of clover and daikon on the existing lawns so that in two or three years the clover would overcome the lawn and the daikon would take root amid the ground cover, interestingly, it was the Asian people and Asian-Americans who said they would try it right away. Most Americans would just laugh and agree with the theory, but they were cautious about putting it into practice. The reason, I believe, is that it would challenge their adherence to ‘lawn’ culture. If they cannot overcome this prejudice, there will be a limit to the growth of family gardens in the United States.”

“It seems that the main goal in the life of the average American is to save money, live in the country in a big house surrounded by large trees, and enjoy a carefully manicured lawn,” wrote Fukuoka. “It would be a further source of pride to raise a few horses. Everywhere I went I preached the abolition of lawn culture, saying that it was an imitation green created for human beings at the expense of nature and was nothing more than a remnant of the arrogant aristocratic culture of Europe…Because residential lots are large in the United States, a family vegetable garden can provide for all the food needs of a typical family, if they are willing to do the work. In Japan, a residential lot about a quarter acre would be enough to allow near self-sufficiency and provide a healthy living environment, but I learned—to my envy—that in many suburban and rural areas of the United States, people are not allowed to build houses on small lots.”

On closer inspection, modern American lawns are more often a biodiverse mixture of turfgrass and flowering plants like clover and dandelions. Kentucky bluegrass lawns may be 30% white clover, which favors native pollinators like bumblebees. Clover and dandelion flowers attract honey bees, bumble bees, parasitic wasps that kill pests, hover flies (syrphids) that eat aphids, and carnivorous rove and ground beetles eating snails, slugs, caterpillars and other pests. Nonetheless, tons of herbicides go onto USA lawns to eradicate clover and dandelions as weeds, often as part of fertilizer and insecticide mixtures.

Turf biodiversity is all well and good, but only as long as the clover and dandelion flower nectar is pure and uncontaminated by pesticide cocktails. Lawns laden with clover and dandelion flowers provide bees and beneficial insects with “a big gulp of nectar,” the University of Kentucky’s Jonathan Larson told the ESA annual meeting in Knoxville, Tennessee. When those “big gulps of nectar” are laced with certain neonicotinoid pesticides, the effects can ripple through the ecological food chain.

When turfgrass pesticide labels say, ‘Don’t treat flower heads,’ “Follow the label to the letter of the law” to avoid poisoning pollinators, said Larson. Or get rid of the flowering plants in the lawn by mowing the turf before spraying. Or delay pesticide sprays until after clovers, dandelions and other lawn flowers have finished flowering. Clover control in lawns using herbicides is difficult, and usually not feasible, Larson told the ESA. Hence, mowing is the preferred strategy for removing flowering lawn weeds before spraying pesticides.

In enclosure experiments with tents confining bees in the turf, mowing the turf before pesticide treatment mitigated the problem, resulting in more bees and more honey. In 2012, bees were tented on clothianidin-treated turf for 6 days and then moved for 6 weeks to a Lexington, Kentucky, horse ranch with unsprayed turf. Clothianidin reduced the rate of bumble bee weight gain, but at the end of 6 weeks the bees were starting to catch-up. But overall, the 6-day pesticide exposure still resulted in reduced bumble bee weight gain, less foraging and reduced queen and hive reproduction several weeks later. Chlorantraniliprole, which has a different mode of action (muscular), did not produce these adverse effects. Larson also told the ESA that clothianidin, a widely used neonicotinoid turf pesticide, also reduces decomposers (detritivores) like soil-dwelling earthworms and springtails more than chlorantraniliprole.

Besides supporting more soil life, more biocontrol organisms, and healthier crops of pollinating bees, you get a healthier turfgrass lawn if you do not need pesticides and do not have to mow so often. “Mowing height is an easily manipulated cultural practice that can have an impact on ecological conditions,” Samantha Marksbury from the University of Kentucky, Lexington, told the ESA. “Taller grass usually supports a more diverse ecosystem and increases natural enemies. Increasing cutting height stimulated deeper roots, yielding a healthier turf with less need for insecticide. Higher mowing height decreases need for irrigation and the canopy prevents water loss.”

Taller turf (raised mowing height) also tends to be more robust and more tolerant of white grubs. Nevertheless, about 75% of turf is lush residential monocultures (mostly one grass species) that is heavily fertilized, dosed with chemical herbicides and frequently mowed, Emily Dobbs of the University of Kentucky, Lexington, told the ESA. However, the ecology of grass cutting or mowing gets quite complex and has seasonal variations. In May, turf with a low mowing height (2.5 inches; 6.4 cm) was hotter, drier, and had the most predatory ground beetles, rove beetles and spiders. Later in the season and Sept/Oct, turf with a higher mowing height (4 inches; 10.2 cm) was cooler, wetter, and had the most predators.

Historically, in the Middle Ages in England, going back many centuries (even before Chaucer) before the age of chemical farming and gardening, lawns were “flowery meads” with roses, violets, periwinkles, primroses, daisies, gillyflowers and other colorful, fragrant flowers interplanted right into the turf. The idea of planting a lawn with one species of grass made no sense, though a camomile lawn or plot came into being for infirmary gardens in England after 1265, as this medicinal aromatic plant helped other plants growing nearby in poor soils and grew faster the more it was trodden.

“There were no flower-beds of the sort familiar to us,” wrote Teresa McLean in her 1981 book, Medieval English Gardens. “The simplest type of flower garden was the flowery mead, wherein low-growing flowers were planted in turf lawns, sometimes walled, sometimes left open, to make a beautiful domestic meadow. The flowery mead was the locus amoenus of God’s beautiful world.”

“Trees were often planted in raised turf mounds, surrounded by wattle fences, which doubled as seats,” wrote McLean. “Medieval lawns, unlike modern ones, were luxuriously long, and full of flowers and herbs; they were fragrant carpets to be walked, danced, sat and lain upon. What modern lawn could find a poet to write about it as Chaucer wrote about the one in the Legend of Good Women?

Upon the small, soft, sweet grass,
That was with flowers sweet embroidered all,
Of such sweetness, and such odour overall…”