We may not be in Kansas anymore, but that doesn't keep us from enjoying the striking symbol of the Sunflower State. These gorgeous flowers form crowns on single stems, having been recorded at heights as tall as 7 meters, and the young flower heads are capable of tracking the sun. Sunflowers belong to the world's largest plant family, Asteraceae, which includes dandelions, thistles, daisies, lettuce, and artichokes, and whose members have composite flower heads. The sunflower head consists of a ring of yellow ray flowers surrounding a large cluster of disk flowers, which, in the words of sixteenth-century English herbalist John Gerard, are “set as though a cunning workeman [sic] had of purpose placed them in very good order.” The disk flowers, after pollination, produce the fruits that we call sunflower seeds.
An extensive discussion of the variation and taxonomy of the sunflower family over the past few hundred years reveals the intensity with which botanists around the globe collect, study, and name new species. Studies using DNA sequencing have helped scientists revise their comprehension of the relationships in the Asteraceae. In fact, the usefulness of DNA in understanding the evolution of all angiosperms originated from research on the Asteraceae.
Asteraceae is considered an ecologically successful family with species comfortable sharing habitats with humans. They are found growing across a wide range of environmental conditions on all continents except Antarctica, and many are found climbing mountains to high altitudes. American botanist James Small even concluded that the Asteraceae “seem to have been formed with the mountains by the mountains for the mountains.”
Humans have utilized herbal medicines for centuries. Asteraceae, which produce a great variety of chemicals in their roots, bark, leaves, flowers, and seeds, have been used in treatments and cures. At one time, for example, coltsfoot leaves were used as an expectorant and parts of marigolds were used as stimulants. Of course, many of the so-called cures of the past were nothing more than quaint folklore. But legitimate scientific research has provided a few drugs originating from these plants. For example, Artemisia has given us antiparasitic compounds; and tarragon produces latanoprost, used in treating glaucoma. Not all the effects of these plants are beneficial, however. Common ragwort is known in Britain as a horse killer, and hay fever is caused by the pollen of various Asteraceae.
After an extensive biological background of the Asteraceae, the author complements the biology with much fascinating historical and cultural information on this plant group. Before sunflowers took center stage in agriculture during the twentieth century because of their importance as a source of oil and protein, it was lettuce varieties that were the most important. The Egyptian deity Min is often shown in pictures and statues accompanied by a plant that scholars believe is a romaine-like lettuce. Caesar Augustus built an altar to lettuce because he felt that lettuce had cured him of a disease.
Asteraceae flowers are symbolic in many cultures. The dark blue cornflower was a symbol of fertility in ancient Egypt and later was associated with the Virgin Mary in iconography. The poppy has become a symbol of wartime tribute during British Remembrance Day celebrations each November. Edelweiss, associated with the Alps, has appeared on Austrian coins and is the title of a sentimental tune in the motion picture The Sound of Music. Numerous postage stamps from many countries feature Asteraceae flowers on them. Vincent Van Gogh's well-known Sunflower series illustrates the variety of sunflower heads. The daisy has been used by writers since the fourteenth century and is found in the works of Chaucer, Shakespeare, Burns, and Carroll. And who does not remember picking off the ray flowers of a daisy while repeating “Loves me, loves me not.” The author advises that “if love is desired, be sure to pick an odd-rayed flower head.”
Part of Reaktion Books' ambitious Botanical series, which presents various plants from a natural and cultural history perspective, this fascinating and exhaustively researched volume is appropriate for college or advanced high school readers. It would be a valuable addition to a classroom library. Profusely illustrated with captivating photographs, it also includes an appendix of plant names, an extensive endnote documentation of the text, a bibliography, a list of associations and websites, and an index.