The common name of Smooth Aster refers to the smooth stems and leaves which makes this species different from most asters. There are several flower stems (with floral arrays) per plant, branching from the main stem, which usually has a whitish bloom and some red streaking. Stems are typically 20 to 60 inches high.
Leaves are alternate, thick, are narrowly lance shaped to ovate, less than or equal to 5 times longer than wide (depending on the variety) and usually clasp the stem, but smaller upper stem leaves may be stalkless but not fully clasping. The lower leaves are sometimes toothed and can have fine hair on the margins. Lower leaves on some varieties will drop early and leaves are generally subject to powdery mildew. Surfaces are smooth and blue-gray color from which comes the common name.
The floral array is a panicle atop the stems with stiffly ascending branches. Flowers are on long stalks.
Flower heads are 1 to 1-3/8 inch wide and composed of two types of florets: An outer ring of 13 to 23+ blue or violet ray florets which are pistillate and fertile. These surround 19 to 33+ central disc florets that are tubular, yellow, bisexual and fertile. The corolla of the disc floret has triangular lobes on the throat which spread slightly when the floret opens. The anthers on the stamens of the disc florets are yellow, with the five stamens tightly surrounding the style, which has appendages at its tip. The style is exserted from the corolla throat when the floret opens. The disc florets turn reddish with age, typical of asters in this genus; each flower has its own fairly long stalk (pedicle). The flower stalks have dark green leafy bracts which are appressed to the stalk. These graduate into 4 to 6 series of phyllaries which are appressed to the flowerhead. The phyllaries are unequal in size and have long dark green tips. The tips can be lance shaped or diamond shaped.
Seed: The seed is a dry 4 to 5 nerved cypsela 2 to 3.5 mm long, with a rose to tawny pappus attached for wind dispersion. Seeds do not need cold stratification and will germinate without delay in a warm location.
Varieties: Two varieties of the four accepted varieties have been reported for Minnesota - var. laeve, which has strongly unequal phyllaries with diamond shaped tips and var. geyeri which has less strongly unequal phyllaries with lanceolate shaped tips. The former is the one found, the latter was last collected in the wild in 1891. Both varieties have leaves that conspicuously clasp the stem with blade length less than 5x the width and are lanceolate to ovate in shape. The other two varieties, not found in Minnesota, have linear to lanceolate leaves, usually 5x the width and slightly clasping. Var. concinnum usually has the basal leaves gone by flowering time and the stem leaves are linear-lanceolate. Var. purpuratum has leaves mostly linear and basal and stem are present at flowering time.
Habitat: Smooth Blue Aster ranges from moist woods to open prairie and is a good plant for prairie restoration, however, when young, the plant is attractive to white-tailed deer; on the good side, it attracts butterflies and other pollinators. In a prairie planting subject to periodic burns, the plant will survive well if the burn is early in the season. It grows from a short rhizomatous root system that develops a thick woody caudex. Full sun to partial sun, wet-mesic to dry-mesic moisture conditions. It self-seeds nicely.
Names: The old name for this aster was Aster laevis. All the new world asters, formerly in the genus Aster, have now been reclassified, most into the genus Symphyotrichum. The genus name is from the Greek symphysis, for 'junction', and 'trichos', for hair and, while obscure, it was first applied by Christian Gottfried Daniel Nees von Esenbeck in the 1800s in describing the type aster for the genus. The species name laeve, is from the Latin meaning 'smooth'. The author names for the plant classification are as follows: ‘A.Löve’ is for Áskell Löve (1916-1994) Icelandic botanist, co-founder of the Flora-Europaea project and professor at various universities in North America. ‘D.Löve’ is for Doris Löve (1918-2000), Swedish systematic botanist, active in the Arctic and collaborator with Áskell Löve on numerous publications. They updated the work of the original classifier - '(L.)' which refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
For comparison, a similar blue aster flower grows in the upland Garden -- the Sky Blue Aster, Symphyotrichum oolentangiense; it has different leaves, a smaller flower and the flower head phyllaries are different. Comparison photos are shown below for other asters with blue ray florets.
Above: The blue to purplish rays surround a central disc of yellow disc florets, both types are fertile.
Below: 1st and 2nd photos - Note the stalkless, partially clasping leaves and the reddish streaks on the smooth stem. 3rd photo - Note the long dark green tips on the small phyllaries at the flower head. Note the longer appressed bracts below.
Below: The difference in size between the upper stem leaves (top leaf) and the lower stem leaves (bottom leaf) is quite distinctive. The larger leaves may have a few teeth as shown here.
Below: The undersurface of the leaves is very smooth but with some fine hair on the margin.
Below: Seeds are a 4 to 5 nerved oblong dark brown cypsela with a fluffy pappus attached for wind dispersion. The bracts on the flower stalk are still visible in the 1st photo, brown, but still appressed to the stalk.
Above & Below: A comparison of 4 blue flowered asters. Besides plant geometry, leaf shape and size, the diameter of the flower head, # of ray and disc florets (upper photo) and the shape of the phyllaries of the flower head (lower photo) help distinguish one species from another.
Notes: Smooth Blue Aster is indigenous to the Garden area. Eloise Butler first catalogued it on Sept. 6, 1907. She also planted this species many times: On Sept. 1, 1912 with plants obtained from Fort Snelling and again on the 26th with plants from Minnehaha Park; more plants in 1914, and then in 1917 on 3 dated in the all she brought in 51 each time (153 total) - not sure why 51 was so important, unless they came from the Park Board nursery in flats. Once in Sept. 1917 Eloise noted "Aster concinnus in bloom." That is one of the 4 varieties of the old Aster laevis, but only found on the East Coast and Eloise never reported bringing in any East Coast plants. It had to be var. laeve. More plants came in, sometimes several times each year, in every following year except 1926, '28 and '32. Martha Crone planted it often in her early years as curator, specifically, 1933, '34, '37, '38, '43, '44, '45, '46, '47, '48, '49, '53. Smooth Aster was listed on Martha Crone's 1951 inventory of plants in the Garden at that time using the former botanical name Aster laevis, the same name used by Eloise Butler.
Smooth Aster is native to much of Minnesota except the Arrowhead and a few other scattered counties. In North America it grows in the eastern half of the continent. Asters are difficult to study. There are twenty-four species just of Symphyotrichum listed by the DNR and the U of M Herbarium as being found in Minnesota, some, including this species, with several varieties.
Eloise Butler wrote about the asters in the Garden in her 1915 report to the Board of Park Commissioners. Of this species she said: "Aster laevis with richly colored flowers, smooth, thick leaves, and sturdy habit, is also still in evidence on dry, sandy soil." Much the same text was incorporated into an essay that was sent to The Gray Memorial Botanical Chapter, (Division D ) of the Agassiz Association for publication in the Asa Gray Bulletin. Text here.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"