Monday, April 22, 2013

Plant Story: Common Dandelions of the World

dandelions, Masonville, Colorado
dandelions, Taraxacum officinale, Colorado, USA
dandelion, Waimea, Hawaii
dandelion, Waimea, Hawaii
    Dandelions, Taraxacum officinale (sunflower family, Asteraceae) are recognized as the quintessential weed in the United States. They are persistent lawn weeds known to just about everyone, at least in the eastern 2/3 of the United States.

    Everyone hates dandelions. Enormous amounts of time and energy have been spent killing dandelions.

     Dandelions haven’t always been weeds. They were almost certainly brought to the United States intentionally as a food plant. The leaves are edible, eaten raw like lettuce or cooked like spinach. 

dandelion, Millford Sound, New Zealand
dandelion, Millford Sound, New Zealand

The flavor is sharp and, by summer, bitter to modern tastes, but 200 years ago most greens were much stronger and less pleasant-tasting than they are today. Dandelion roots are edible. Again, they are smaller and more fibrous than carrots or radishes, but reportedly taste okay when cooked. They have also been dried and ground to make a coffee-like beverage. The flowers can be gathered and made into a wine. Having tried that, I recommend using just the yellow petals not the green bracts or you carry over a lot of bitterness. One of the best homemade wines I ever made was dandelion wine. Flowers and roots can also be fried. Eaten raw, the plant is a diuretic (causes urination) and it has been used medicinally for centuries. Compilations of folk remedies report a wide variety of medicinal uses of dandelions. My authority on medicinal plants, the PDR (Physicians Desk Reference) for Herbal Medicines reports that Germany's Commission E, which carefully checks medicinal plants, has approved dandelions for dyspeptic complaints, infections of the urinary tract, liver and gallbladder complaints and loss of appetite, so this weed is still a medicine, even applying modern standards of efficacy. 

  Note: DO NOT eat any dandelions unless you KNOW they have NOT been sprayed with herbicides or any other potentially toxic chemical. Alas, its not just plant toxins we have to beware of, but also things sprayed or poured on the plant or into the environment generally.
dandelion, Hagi, Japan
dandelion, Hagi, Japan

     Some time ago, dandelions went out of fashion as a food. Lettuce, cabbage, spinach and chard became the leafy vegetables of choice. During the 20th century most people came to rely on pharmacies for medicines and no longer gathered their own. Consequently dandelions had to make it on their own, without the benefit of people planting them. Because they have many small wind-borne seeds, they succeeded admirably and became regarded as weeds. 

     Not all plants brought to the U.S. by European settlers flourished after people stopped cultivating them. One that I’m aware of that died out without cultivation is cultivated flax, Linum ultissimum. Planted in field after field in eastern Nebraska from the 1880s, keeping multiple linseed oil mills busy, it vanished soon after cultivation stopped.

dandelion, Helsinki, Finland
dandelion, Helsinki, Finland
    One reason dandelions are so successful is that they are apomictic. That means that the seeds are made asexually. In the flower the tissue closes around one of its cells, the “parachute” forms and the new seed is ready to go. No need to have another plant anywhere nearby. No need for sperm in the pollen carried by an insect to an egg in the ovule. This does mean the seeds are genetically identical to the parent plant and, if the conditions were to change, lack of variation might be a handicap. But if your lifestyle is hopping between lawns, water and fertilizer provided by the humans, apomixis can work very, very well.

    Apomictic reproduction in dandelions does make you wonder why there’s the attractive yellow flower. Maybe it helps the seeds get up and ready to fly faster. Maybe it is a carryover from ancestors that were normally sexual--most plants are sexual, in which the formation of seeds requires the union of sperm and egg. Researchers report that, very occasionally, dandelions cross with their sexual relatives, so perhaps that is why these asexual plants still have a pretty flower.

dandelions, Abisco, Sweden
dandelions, Abisco, Sweden
   Years ago a speaker from Manhattan Kansas described finding flowers in bloom there every month of the year, making the point that the climate there was quite variable. Naturally that set me watching in Lincoln, Nebraska, latitude 40  N, 125 miles nearly due north of Manhattan. I saw flowers in 11 months pretty quickly, but not January. But then we had a year when it was unusually warm for a week in January and I saw a dandelion flower. I admit the plant was on campus, between buildings where it was probably warmed by building exhaust, but flower it did. So other reasons for dandelion success include rapid growth and tolerance of a wide variety of temperatures. 

     Taraxacum officinale is not the only plant in the genus Taraxacum. 515 valid species names are recognized on the Plant List and species are still being discovered, high in the mountains of Italy, for example, or on the steppes of Asia. Native, non-weedy dandelions are found all over the world. There are two native to the Rocky Mountains of Colorado, Taraxacum eriophorum woolbearing dandelion and Taraxacum lyratum
harp dandelion. 

     The number of species of Taraxacum is actually a difficult problem. Apomixis means that there are lots of lineages of dandelions that do not cross with any other lineage. Should each be called a species? Not never: there will be a time when enough mutations accumulate for the plants be genetically and physically quite distinct. But putting every plant you see or the plants of every county into a different species is truly impractical. The Angiosperm Phylogeny says "60-500" species of Taraxacum, which pretty well describes the problem. Generally, other species of Taraxacum are recognizably different from "common dandelions." Taraxacum officinale is distinctive worldwide, even though the dandelions of Sweden are pretty well isolated from those of Hawaii. Knowing what I know now, I won't swear some of the dandelions in my photos aren't some species other than T. officinale, but it is a lot easier to find T. officinale in the touristy spots around the world than any of its relatives. Taraxacum officinale is reported as a weed in pretty much all the world except tropical Africa. 
dandelions, Tuscany, Italy
dandelions, Tuscany, Italy

     Where Wiggers, who chose it in the late 18th century, got the name Taraxacum is not known. The following have been suggested: from the Arabic name, tarachakum "wild cherry," or tarakhshaqun "wild chickory" or a variation on tarashqun "bitter herb" or from the Greek for taraxis an eye disorder, tarassen or tarassos "disorder," or trogimon, "edible." Gerard, in his herbal (1600), writes the dandelion is called "in the shops, Taraxacon" which fits the name Wiggers gave it well (see next paragraph), but doesn't explain much else. 

dandelions, Reykjavik, Iceland
dandelions, Reykjavik, Iceland
   The species name, officinalis, is the genitive of the Latin, officina, and means "of the workshop." That is, this is the dandelion for sale in shops. The fact that it is for sale generally refers to a plant with medicinal uses, but one should remember that historically virtually all medicines were plant products. Thus officinalis is seen on plants that are quite toxic, such as the peony, Paeonia officinalis, ones that are not used much medicinally today, for example asparagus, Asparagus officinalis, to current medicinals such as hyssop, Hyssopus officinalis and quinine, Cinchona officinalis. What officinalis usually also signals is that this is the common or familiar member of the genus, as the English names often indicate: Althaea officinalis is called the common marshmallow and Anchusa officinalis the common bugloss.

     Dandelions are pretty widely called dandelion, or dent de lion, lion's tooth. Of course that could refer to the deep "teeth" of the leaf, the shape of the flower close up, or the long tap root (like pulling teeth). Really. Other places and times, the plant has been called piss-a-bed (or variations on that) because of its diuretic properties, blowball, puffball, wild endive and dumbledore. 

dandelions, Ushuaia, Argentina
dandelions, Ushuaia, Argentina
 (southernmost South America) 
     How the common dandelion reached North America is a confused story. It is believed to have originated in Asia Minor, specifically somewhere between Greece and the western Himalayas, and spread from there. But that was very long ago: fossil dandelions are known from the last Ice Age. Clearly it spread across Europe and Asia as opportunity presented itself. But how and when did it cross the Atlantic? Opinions include: 1) about 10,000 years ago over the Bering land bridge, 2) about the year 1000 AD with the Viking settlement in Newfoundland, 3) in 1620, with the Mayflower...Even if it came really early, it was not very widespread until relatively recently. The earliest record in New England is 1672, in Canada 1821. Settlement and agriculture in North America dramatically increased the habitats suitable for dandelions and human travel carried the plants to those areas. It is currently found in every state in the U.S. and every Canadian province. My guess is that it is equally ubiquitous in Europe and New Zealand. Weed books show it across South America, and, well, all over the world except equatorial Africa.

dandelion, Lincoln Nebraska
dandelions, Lincoln, Nebraska, USA
     My photos show you places I have seen dandelions. However, they do not really grow everywhere. Knowing their wide distribution, long ago, for a project on genetic variation, my friend Yan Linhart, professor of biology at the University of Colorado, Boulder, asked me to collect dandelions as I drove Interstate 80 from Lincoln, Nebraska to San Francisco. It turned out to be a difficult assignment. Dandelions are lawn weeds. In the arid west--across Wyoming, Utah and Nevada--they were uncommon. They  reappeared in the lawns of California. 

   One species or many microspecies, asexual but making flowers that attract insects, very useful but hated...there's much more to dandelions than meets the eye.

Comments and corrections welcome.

Sources (places I checked my facts)
Fernald, M. L. 1950. Gray's Manual of botany. Van Nostrand, New York
Gerard, J. 1975. The Herbal or General history of plants. 1633 edition revised and enlarged by T. Johnson. Dover      Publications, New York. 
Great Plains Flora Association. 1986. Flora of the Great Plains. University of Kansas Press, Lawrence.
Gruenwald, J., T. Brendler, and C. Jaenicke, eds. 2007. PDR for Herbal Medicines. 4th edition. Thompson Healthcare Inc., Montvale New Jersey 
Harrington, H. D. 1967. Edible native plants of the Rocky Mountains. University of New Mexico Press, Albuquerque.
Holm, L., J. Doll, E. Holm, J. Pancho and J. Herberger. 1997. World Weeds. Natural histories and distributions. John Wiley & Sons, New York.  
The Plant List
Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 12, July 2012 [and more or less continuously updated since].
USDA plants webpage

Kathy Keeler, A Wandering Botanist
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