Panicled Aster

Appearance

This perennial herb has a thick, erect stem that often grows 1.5 meters tall or more, sometimes approaching 2 meters. It has a stout rhizome and can spread to form a colony.

The leaf blades have winged petioles and may sheath the stem at the bases. The largest, near the base of the plant, are up to about 15 centimeters long. Those higher on the stem are smaller. The lower leaves may have toothed edges.

The inflorescence is usually a large, branching array of many flower heads of varying size. There are 16 to 50 ray florets per head, each measuring 3 to 14 millimeters long, in shades of blue, pink, or white. The disc florets bloom yellow and turn purple.

The species seems quite variable. Plants with larger, blue-rayed heads superficially resemble S. robynsianum, but differ in less clasping leaf bases, more imbricate phyllaries, and tendency to shorter leaves and more heads. Such plants represent S. lanceolatum var. hesperium (A. Gray) G. L. Nesom and are known from Benzie, Delta, Manistee, Osceola, and Schoolcraft Cos. Plants with pubescence uniform (rather than in lines, or absent) on the middle and lower internodes have been named var. hirsuticaule Semple & Chmiel. Plants with quite small heads (involucre under 5 mm long), very numerous and crowded on branches of the inflorescence, have been called var. interior (Wiegand) Semple & Chmiel. Plants with stems glabrous or pubescent only in lines and with heads not crowded include plants with broadly oblanceolate leaves (var. latifolium (Semple & Chmiel.) G. L. Nesom) and plants with narrow, linear to oblanceolate leaves (var. lanceolatum). These last four varieties appear to be widespread, but we have no abundance data.

Sometimes this species is confused with S. pilosum, and indeed these two species appear to hybridize, but besides its unique phyllaries, involucre shape, and cespitose habit, Symphyotrichum pilosum tends to have the pappus of the disk florets shorter than the corollas, while in S. lanceolatum and its allies, the pappus equals or exceeds the disk corollas. Plants intermediate with S. puniceum and especially S. firmum seem to be more frequent than some supposed hybrids. And a number of plants resembling S. lanceolatum but with deeply lobed disk corollas presumably have resulted from hybridization with S. lateriflorum.

Naming

Symphyotrichum lanceolatum (Willdenow) G. L. Nesom
Aster lanceolatus Willdenow

Accepted varieties:
Symphyotrichum lanceolatum (Willdenow) G. L. Nesom var. lanceolatum
Symphyotrichum lanceolatum (Willdenow) G. L. Nesom var. hesperium (A. Gray) G. L. Nesom
Symphyotrichum lanceolatum (Willdenow) G. L. Nesom var. hirsuticaule (Semple & Chmielewski) G. L. Nesom
Symphyotrichum lanceolatum (Willdenow) G. L. Nesom var. interior (Wiegand) G. L. Nesom
Symphyotrichum lanceolatum (Willdenow) G. L. Nesom var. latifolium (Semple & Chmielewski) G. L. Nesom

Distribution

''Symphyotrichum lanceolatum'' is native to much of Canada excepting the far north, to most of the United States, and to northwestern Mexico in Baja California, Sonora and Chihuahua. The species has been introduced and naturalised in many parts of Europe, from Belgium to Serbia to Latvia.

Habitat

In its native range, ''Symphyotrichum lanceolatum'' occurs in a wide variety of mostly moist, open habitats, including riparian areas, meadows and ditches. As an introduced species in Europe, it occurs in disturbed man-made habitats, as well as in riparian areas as an invasive species.

Predators

The species is visited by a wide variety of pollinating insects, including bees, flies, moths and wasps. Cross-fertilisation is usually required to produce viable seed, and as such large clones may have low seed production.

Several gall midge species are known to form galls on ''S. lanceolatum'', including ''Rhopalomyia asteriflorae'' and ''Asteromyia paniculata''. Leaf-mining insects known to feed on this species include ''Anoplitis inaequalis'', ''Agromyza curvipalpis'', ''Phytomyza albiceps'', ''Microrphopala xerene'', and ''Sumitrosis inaequalis''. Younger instars of Gorgone Checkerspot caterpillars will feed on ''Symphyotrichum lanceolatum''.

Uses

''Symphyotrichum lanceolatum'' may be a minor weed in agricultural fields.

Within its native range, the species was used by indigenous peoples for a variety of medicinal purposes. In the American Southwest, the Zuni people used this plant for wounds and nosebleed. The Iroquois in what is now Eastern Canada used it to treat fever.

''Symphyotrichum lanceolatum'' is also cultivated as an ornamental garden plant and may be used in the cut flower industry.