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Idaho Mountain Wildflowers

Aster (Sunflower) Family, Asteraceae

The Sunflower, or Aster Family, Compositae or Asteraceae, (all of these are correct. although Asteraceae is preferred today for the family name) is the largest family of flowering plants. Members have one common characteristic: each bloom is made up of many tiny flowers. Those in the center of the flower head are “disk flowers,” and those on the edge—each with a single strap-like petal—are “ray flowers“. Ray flowers may occupy the entire flowerhead; conversely, some species have only disk flowers. The Asteraceae have other characteristics that may help with identification. These include protruding, split styles; multiple, pointed, small leaves or “bracts” that surround the base of the flowerhead; and a pappus attached to each seed that may aid in seed dissemination (as, for example, with dandelions). It is not always easy to recognize members of the aster family, for some are atypical or resemble other flowers. Garden ornamentals include zinnias, chrysanthemums, daisies, and asters, to name only a few. Lettuce and artichoke are edible members of the family. Food oils are obtained from sunflowers and safflowers. Others are troublesome weeds: ragweed, knapweed, burdock, dandelion, etc..  It would take a sizeable book to describe all of the members of the family that occur just in Idaho; the examples pictured here are a sampling of composites that grow in our mountains. Listing wildflowers by color as we have done here can be deceiving, for colors range greatly. With the Asteraceae, however, where color is relatively constant, it can help with identification.

Purple daisy-like flowers

Note: Fleabanes, or true daisies (Erigeron spp.), have regular bracts--the leaves that cup the flowerhead--tend to bloom early in the summer, and while many are purple, they more often are yellow or white.

The Rough (Idaho) fleabane, Erigeron asperugineus ( D.C. Eaton) A. Gray (left).The rough fleabane is a lovely little plant distinguished by its many rayed purple and yellow flowers. It blooms in summer at high elevations on rocky ground. The genus name, Erigeron, is an old one, derived from the Greek: eri meaning “early“ and geron for “old man,” evidently because many flowers have grayish hairy leaves and stems. Our plant’s species name asperugineus means “rough” referring to brittle-feeling  stems and crisped leaves.

Bear River fleabane, Erigeron ursinus D. C. Eaton (right), The Bear River fleabane is larger and showier than most erigerons. It is characterized by a basal cluster of narrow lanceolate leaves, and narrow stem leaves. The stem is stout, bearing a single flowerhead. A broad yellow disk is surrounded by 100 or so purple rayflowers. The Bear River, from which the plant’s name was derived, flows from Utah’s Wasatch Range to Bear Lake on the Idaho-Utah border, and thence to the Great Salt Lake. The Latin species name, ursinus, means “bear.”

The Showy Daisy (or Fleabane), Erigeron speciosus (Lindl.) DC (left). The showy daisy is a common plant in our mountains where it grows in large clusters crowded with many flowerheads. These are about two inches across, with 60 to 150 narrow rays that range in color from purple to nearly white. Alternate lanceolate leaves ascend the stem. “Aspen daisy” has been suggested as a standardized common name for the plant. David Douglas introduced the showy daisy into England and it is grown there today as an ornamental. The name speciosus means “splendid.” The plant is common throughout the West, (although it does not occur in California).

Foothill, or long-leaf daisy, Erigeron corymbosus Nutt. (right). As one of its common names suggests, the long-leaf daisy is a commonly encountered foothill plant (although it occurs as well at higher elevations). It prefers dry ground and is usually found in the company of sagebrush. The plant can be identified by its many rays (+/- 100)  and long linear leaves that ascend the stem. The long-leaf daisy is found in all of the states and provinces contiguous with Idaho's borders, excepting Nevada. The species name was derived from the word "corymb" which implies a flat-topped cluster, apparently referring to this plant's disk.

Mountain townsendia, Townsendia alpigena  Piper (right). The townsendias are closely related to the fleabanes. The mountain townsendia is a small plant that grows at, or above treeline on alpine tundra. The plants are characterized by relatively large flowerheads borne singly on longish stems. Their central disks are prominent, and the rays range from a light purple color (usually) to near white. Its small basal leaves are covered with fine hair and the involucral bracts below the flowerhead are striped, a distinguishing feature. Twenty seven species of Townsendia are recognized; none grow east of the Mississippi River. David Townsend (1787-1858), for whom the genus was named, was an amateur Pennsylvania botanist.

The "asteroids" (plants formerly in the genus Aster), include Symphyotrichum, Ionactis, Eucephalus, Machaeranthera, and several other genera. These have irregular "shingled" bracts below the flowerhead, tend to bloom later in the summer than the fleabanes, and most are purple.

Leafy aster, Symphyotrichum foliaceum (Lindl. ex DC.) G. L. Nesom var. apricum (A. Gray) G. L. Nesom (left). The leafy aster is found throughout the West, blooming from mid-summer on. They have large, stemmed, basal leaves and smaller “clasping” (stemless) leaves higher up. Each stem bears one flowerhead, often with fifteen rays. As the flowers mature, the central bright yellow disk becomes brownish, and the petals darken to a rich, deep purple—a distinguishing feature. Several varieties are recognized by minor differences in their morphology. Var. apricum, (“apricum” means “sun-loving”), the plant shown here, has purple-margined bracts (the small leaflets that cup the flowerhead). It is common along our trails. The plants bloom from mid-summer on

The Hoary Aster, Machaeranthera canescens var canescens (Pursh) A. Gray (right).  Machaeranthera is a word derived from the Greek, meaning "sword" plus "anther,"  referring to its sharp-pointed anthers. The plants bloom in summer's heat from the end of July well into August, always in dry places. It has adapted to a xerophytic life with a furry stem (canescens means "covered with short white hairs") and spiny bracts. These and its white-based purple rays, and orange disk help to identify it. Many varieties are recognized. Meriwether Lewis collected a hoary aster (another variety, incana, that grows more to the west) on the Columbia River in October of 1805.

The Elegant Aster, Eucephalus perelegans (A. Nelson &J. F. Macbr.) W. A. Weber (left), formerly Aster perelegans, blooms from mid-summer into September as high as the subalpine zone. It is conspicuously few-rayed (usually 5 or 8), and a rather ragged appearing flower, making the plant easy to identify.  The elegant aster was collected by botanist Thomas Nuttall, then on the faculty of Harvard College, in 1834 as he traveled the Oregon Trail in the company of Boston businessman Nathaniel Wyeth for whom the wyethias were named.

Rocky Mountain aster, Ionactis stenomeres (A. Gray) Greene (right).  Formerly classified as Aster stenomeres, the Rocky Mountain aster's attractive flower-heads bear thirteen (or occasionally more) narrow rays. The word stenomeres, from the Greek, means “narrow-parts” presumably referring to its narrow, same-sized leaves that ascend the stem. Ionactis is also derived from the Greek, and means “violet rays” (cf. “actinic”). This plant is often seen growing in aggregates as shown here

Alpine aster, Ionactis alpina (Nutt.) Greene (left). The trouble with common names is that they are often duplicated; as an example two “alpine asters” are shown here. Ionactis alpina grows in large clumps on dry ground, usually in the company of sagebrush, as high as the subalpine zone. Characterized by small, clustered gray-green leaves and thirteen or so rays, it was previously classified as Aster scopulorum.

Alpine aster, Oreostemma alpigenum (Torr. & A. Gray) Greene var. haydenii (Porter) G. L. Nesom (right) is a subalpine to alpine species that also grows in clusters in open spaces. Botanists recognize three varieties; only this one grows in Idaho. The plant has a basal crown of linear gray-green leaves. These, the stem, and purple-tinged bracts are covered with fine hair. The generic name Oreostemma, derived from two Greek words, means “mountain crown.” To avoid confusion with other alpine asters the name “tundra mountain crown” has been suggested for this plant.

Western mountain aster, Symphyotrichum spathulatum (Lindl.) Nesom var. spathulatum (left), formerly  classified as Aster occidentale (Nuttall) Torr. & A. Gray. The western mountain aster is a fairly common mountain wildflower. It ranges in height from about 6" to 18" depending on its situation--when clustered, the plants tend to be shorter. The upper stem leaves are narrow; those toward the base are broad--a distinguishing feature. The plants often bear many flowerheads, as shown here. The western mountain aster grows in all the mountain states, from New Mexico northwards to Mackenzie in Canada. Here is an example of a plant having an established name reclassified when an earlier name is found.

Thick-stem aster, Eurybia integrifolia (Nutt.) Nesom or Aster integrifolius Nutt. (left, right). Confusingly, both binomial names listed are currently in use. This is a mid-elevation mountain plant that blooms in mid-summer on dry gound. Tall for an aster, its stems arise from a cluster of large, smooth-edged (integrifolia) leaves. Each stem divides into several to many stemlets that bear small (<1" diameter) purple-rayed flowerheads. These have from 10 to 27 ray flowers, and a raised, yellow disk. The involucre that cups the flowerhead is made up of a row of wide outer bracts and darker, narrower, inner ones. The thick-stem aster is found in the four northwestern states,  and in Wyoming, south to Utah, Nevada and California.

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