White Panicle Aster is a native erect perennial aster that grows to 5 feet in height, stems are stout, grooved, and which can have fine hair, especially near the top, in the grooves of the stem.
Leaves: As the species name and the alternate common name implies, the leaves are lance-like, very linear, up to 6 inches long. They are smooth and entire on the margins or with a few small teeth, and are stalkless (sessile) or somewhat clasping. Largest leaves are near the center of the stem. Dead leaves remain on the stalk for a time and are noticeably curled. Lowest leaves fall off at flowering time (however, in Minnesota during moist cool years, most leaves remain green well into the flowering period).
The floral array is an open spreading, branched panicle with ascending branches (which shape yields the current common name) of small white flowers. The flowers occur on all sides of the branches, unlike the Side-flowering Aster, Symphyotrichum lateriflorum, where the white flowers are in one plane on the panicle branches.
Flowers: Heads are up to one inch wide, but usually 1/2 to 3/4 inch, consisting of two types of flowers: The outer ring of 17 to 47 ray florets (with spreading rays that are usually white) which are pistillate and fertile and which surround 16 to 38 tubular disc florets which are bisexual and fertile. These have whitish to yellowish corollas, turning reddish to purplish at maturity, similar to many of the asters in this genus. The five corolla lobes are mostly erect or may bend outward slightly when the floret opens. Anthers of the five stamens tightly surround the style which is greatly exserted from the corolla when the floret opens. The phyllaries around the outside of the flowerhead are in several series, linear, the outer series 1/3 to 1/2 the length of the inner series. These have dark green center stripes. Below the flower head are 1 to 3 small bracts that do not grade into the phyllaries.
Seed: Fertile flowers mature to a 4 to 5 nerved dry cypsela, 0.5 to 1.6 mm long, with a whitish pappus attached for wind dispersion. These seed heads are rounded and look like small dandelion seed heads. Seeds are very light, about 150,000 to the ounce and will germinate in a warm location, usually without the need for cold stratification.
Varieties: Four varieties of of the five recognized varieties of S. lanceolatum are reported for Minnesota, the variety listed above plus var. hisperium, var. hirsutiicaule, and var. interior. Differences between the first and the next two are in the phyllaries. The next two have differences in the stem. The 4th variety, var. lanceolatum has a difference in the number of flower heads and is considered the most northern of the varieties in North America and the most prevalent within Minnesota. (See Ref. #28b and 28c for distribution and W7 for details of the differences.)
Habitat: The plant grows from a rhizome with fibrous roots and forms colonies in moist low areas that can be in open woods or full sun if the soil is moist. Soil does not have to rich. It attracts butterflies, moths, and bees. This was a common tall grass prairie plant.
Names: Like most new world asters, it has undergone a series of scientific name revisions. It was once Aster paniculatus in Eloise Butler's time, and sometimes Aster lanceolatus, then Aster simplex. 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', all of which relates to a fine division by botanists of certain plant characteristics. The species lanceolatum means 'spear shaped' and refers to the leaf shape. The author names for the plant classification are as follows: The first to classify was ‘Willd.’ which is for Carl Ludwig Willdenow (1765-1812), German botanist, a founder of the study of the geographic distribution of plants. His work was amended by ‘G. L. Nesom’ is for Guy L. Nesom (b. 1945) American botanist who has published papers on the nomenclature of asters.
Comparisons: Asters that have similar looking branched panicles would be the Heath Aster, Symphyotrichum ericoides; the Arrow-leaved Aster, Symphyotrichum urophyllum; and the Calico Aster, Symphyotrichum lateriflorum. The Heath Aster has smaller flowers and very small leaves. The Calico Aster has only 9 to 15 ray flowers which are located on one side of a branch and the leaves are more oval. The Arrow-leaved aster is most similar in the appearance of the flower panicle except that the flowers can be only half the size. See photo comparison below. The leaves are also have arrow-shaped bases.
Above: The flowers of White Panicle Aster have 17 to 47 ray florets (usually white) surrounding 16 to 38 disc florets that are whitish to yellowish, turning reddish to purplish at maturity.
Below: The floral array is an open spreading, branched panicle
Below: 1st photo - The stem has noticeable grooves and leaves are sessile or slightly clasping. 2nd photo - the longest leaves are at mid-stem, usually with smooth margins.
Below: 1st photo - The phyllaries of the flowerhead are in several series, linear (4-6mm long) with dark green centers. Below them on the stalk are 1 to 3 small leaf-like bracts. 2nd photo - Stem leaves are longest at mid-stem, may have a tooth or be entire. 3rd photo - A characteristic of this species is that dead leaves on the stem assume a spiral curl.
Below: The seed is a dry flat cypsela that has a tuft of hair for wind dispersion. These seed heads are rounded and look like small dandelion seed heads.
Below: Both the White Panicle Aster and the White Arrowleaf Aster have erect panicles filled with white flowers. The key difference is the size of the flower and the shape of the phyllaries. Here you see the extremes - a very large White Panicle and a very small White Arrowleaf.
Notes: The White Panicle Aster is indigenous to the Garden, Eloise Butler catalogued it on Sept. 6, 1907 using the name in use at that time, Aster paniculatus. She also transplanted some plants from the current Minnehaha Park area to the Garden on Sept. 22, 1912; from Western Ave. on Aug. 31, 1914 and on two occasions in 1917; in '18 and '20 from Glenwood Park and in '19 from Ft. Snelling. Martha Crone planted it in 1934 and 1938. She also listed it on her 1951 Garden census. Years later and into the early 2000's it was classified as Aster simplex.
In North America White Panicle Aster is found in Canada from Alberta to the east coast and in the U.S. from the Great Plains eastward to the coast, with only Alabama, Georgia and Florida excepted. Within Minnesota it is found in all but 15 counties and most of the exceptions are in the SW quadrant. 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, such as this species, with several varieties.
Eloise Butler in her 1915 report to the Board of Park Commissioners wrote about the asters in the Garden and of this species she wrote: "Aster paniculatus [see name notes above] is often mistaken for Boltonia in the distance. The inflorescence, however, is not flat-topped like that of Boltonia, and the disc-flowers are of a deeper color. This aster is highly decorative, growing as it does in large masses." 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"