By Marion Lobstein
This time of year, late summer into early fall, the wildflowers we enjoy (or may not enjoy in the case of ragweed allergy sufferers) are dominated by members of the composite family Asteraceae. From Northern Virginia out to the upper part of Shenandoah National Park (SNP), there are approximately 150-200 species of composites that bloom from September into late autumn. Of these species, roughly one quarter are species of two genera – approximately 25 species of goldenrods (Solidago and Euthanmia) and 25 species of asters (now transferred to a number in genera). In this article, the “aster” species will be the focus. Goldenrods will be covered in other articles to be posted on the “Botanizing with Marion” web link found at http://pwws.vnps.org.
The term “aster” is derived from a Greek word for star and refers to the shape of the flower head. In the 1990s-based analysis of the genetic material of many species of asters, scientists concluded that true species of the genus Aster are Eurasian species and that our North American native species should be reassigned to other genera. Differences in the flower structure and fruits also were used in the process of splitting up the Aster genus. In our area (Northern Virginia through the upper half of SNP), approximately 25 native species of asters are divided into five genera—Doellingeria, Eurybia, Ionactis, Oclemena,and Symphyotrichum. Only A. tataricus, a naturalized species from Asia remains in the genus Aster. The history of these “new” genus names will be discussed in the accompanying article on the taxonomic history of the “aster.”
Virtually all of our “aster” species are perennials with alternate leaves and often, prominent basal leaves. Most species have fibrous root systems and some species have rhizomes (underground storage stems). As composites, the flower heads (capitula) made up of many separate flowers with a leafy cup or involucre of bracts (modified leaves) (called phyllaries) on the lower surface of the head. In “aster” species, flower heads are made up of both petal-like ray flowers that can vary in color from white to pink to blue to purple as well as tubular disk flowers that are usually yellow but can turn purple to brown with age. In various species of “asters,” these ray flowers are pistillate (female) flowers that can be pollinated and produce fruits while in other species they may be sterile. The disc flowers are perfect (bisexual with male and female structures) and are fertile. In both types of flowers the typical flower parts the 5 petals are fused into a corolla (forming a ligulate or tongue-like “petal” in the ray flowers and a tube in the disc flowers). The sepals are modified into bristle-like pappi (pappus, singular term) that assist in wind dispersal of the fruits. If stamens are present they are 5in number and the anthers unite to form a ring around the style of the pistil of the female structure. The female part or pistil has an inferior ovary (below the attachment of the pappi or modified stamens and the corolla), an elongated style, and a stigma with two branches. These inferior ovaries are embedded in the base or receptacle of the flower head or capitulum.
All flowers of this genus are pollinated by insects such as bees, bumblebees, butterflies, moths, wasps, beetles, and even flies. Species such as the New England aster are often used in butterfly gardens. The “Butterfly Website” is a good website for flower species for butterfly gardening. (You may also want to note PWWS’s forthcoming updated brochure on Butterfly Gardening, which will also be made available on our website, pwws.vnps.org.) Mature aster flower heads that contain dry fruits called achenes or cypelae sport a variety of shapes and are important in identification of species. In these fruits, there is only a single seed closely surrounded the seed coat (derived from the ovary wall). The bristle-like pappi aid in the wind dispersal of fruits of “aster” species (http://www.scientificjournals.org/journals2007/articles/1001.htm).
Medicinal and culinary uses of asters have been more limited than that of other groups of composites. However, the young leaves of the large-leaved aster are recommended as greens in edible plant books. Various American Indian tribes did use native species of asters for a wide variety of medicinal purposes ranging from teas to dried leaf/root preparations to treat fevers, diarrhea, stomach problems, pregnancy complications, colds, wounds and abrasions, skin eruptions (such as in poison ivy dermatitis), nosebleeds, and a host of nervous system complications such as epilepsy and mental illness. The Iroquois used a preparation as a love medicine or potion. Other tribes burned dried aster flowers as incense to attract game such as deer or to drive away evil spirits.
It seems a daunting challenge to identify aster species with traditional wildflower guides such as Peterson’s or Newcomb’s, even older floras. To learn the “new” names is an additional challenge, but will help to keep our minds sharp! It is well worth the effort to identify these beautiful species of composites found in our area. A chart of our species of “asters” with name changes is included in the taxonomic history, below.
[Composite flower drawing: Anon., http://www.horticulture.Lsu.edu]