Overview

Comprehensive Description

Description

This herbaceous perennial plant is ½–2' tall, producing one or more leafy stems that are erect, ascending, or sprawling. The wiry stems branch sparingly, and they are often curved, arching, or crooked. Young stems are whitish green to silver-colored and terete; they are moderately to densely covered with fine pubescence. Older stems are brown or purple and sparsely to moderately covered with fine pubescence. Alternate leaves occur along the entire length of each stem, becoming slightly smaller in size as they ascend. The leaves are ½–1¼" long and about 4-8 mm. across; they are oblong to elliptic in shape and entire (smooth) along their margins. The bases of leaves are sessile or clasp their stems slightly, while the tips of leaves are short-acute. Both the upper and lower surfaces of leaves are whitish green to silver-colored; they are moderately to densely covered with appressed fine pubescence. The upper stems terminate in one or more flowerheads. On a robust plant, this inflorescence resembles a little-branched open panicle up to ¾' long that has 6-18 flowerheads, otherwise the inflorescence consists of 1-2 short branches with 1-3 flowerheads at their tips or slightly below. The wiry branches of the inflorescence are terete, whitish green to silver-colored, and moderately to densely covered with fine pubescence. Along the branches of larger inflorescences, there are leafy bracts that resemble the alternate leaves. The daisy-like flowerheads are about 1¼" across, consisting of 10-22 ray florets that surround numerous disk florets. The petaloid rays of the flowerheads are linear-oblong in shape, widely spreading, and lavender, deep lavender, or various shades of purple. The tiny corollas of the disk florets are tubular in shape with 5 lanceolate lobes along their upper rims; these lobes are erect to ascending. During the period of bloom, the corollas of the disk florets are white to pale pinkish purple; their anther tubes are yellow and their stigmas are lavender to purple. The blooming period occurs from late summer into autumn, lasting about 1 month for a colony of plants. Afterwards, the florets are replaced by achenes. These achenes are 2-3 mm. long and bullet-shaped with small tufts of hair at their apices; they are dispersed by the wind. The root system is fibrous and occasionally rhizomatous; older plants form short caudices. Occasionally, clonal offsets are produced from rhizomes. Cultivation
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Source: Illinois Wildflowers

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This is a truly beautiful little plant with attractive foliage and flowerheads. It's an excellent candidate as a wildflower in a sunny rock garden. In Illinois, Silky Aster (Aster sericeus) can be distinguished from all other asters (Aster spp.) within the state by its exceptional foliage, which has a silvery or silky appearance because of the numerous fine hairs covering its stems and leaves. It also has larger flowerheads (often exceeding 1" across) than most native or naturalized species of asters within the state. Many asters of North America, including Silky Aster, have been reassigned recently to the genus Symphyotrichum. As a result, many authors now refer to Silky Aster as Symphyotrichum sericeum. Return
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Distribution

Range and Habitat in Illinois

The native Silky Aster occurs primarily in the northern tier of counties and in many counties along the Illinois and Mississippi Rivers (see Distribution Map). It is an uncommon plant that appears to be declining in abundance as a result of habitat destruction. These habitats include upland dolomite prairies, gravel prairies, sand prairies, hill prairies, stabilized sand dunes, upland sandy savannas, limestone glades, and prairie remnants along railroads. This is an indicator plant of high quality habitats in dry open areas. Faunal Associations
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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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Physical Description

Morphology

Description

Perennials, (20–)30–70 cm, cespitose, eglandular; with short, woody, cormoid caudices, or short rhizomes. Stems 1–5+, ascending to erect (thin, grayish brown to dark brown), glabrous proximally, densely canescent distally. Leaves (silvery) firm, soft; basal withering by flowering, sessile, blades (1–3 nerved) elliptic-lanceolate, 10–40 × 5–15 mm, bases cuneate, weakly sheathing, margins usually entire, rarely remotely serrate, piloso-ciliate, apices acute, faces less copiously hairy than cauline; proximal cauline withering by flowering, sessile, blades oblanceolate or oblong to linear-lanceolate, 15–30(–50) × 4–10 mm, slightly and progressively reduced distally, bases rounded, sub­clasping, margins entire, silky-pilose, apices obtuse to acute, mucronulate, faces sparsely to densely silky-pilose; distal sessile, blades lanceolate, 10–30 × 5–8 mm, little reduced distally, bases cuneate, margins entire, apices acute, mucronate, faces ± densely silky. Heads in open, paniculiform arrays, branches sparse, fastigiate, often arching (1–5+ per branch). Peduncles subsessile or 0.5–3(–5) cm, densely sericeo-strigose, bracts crowded, 4–8(–10) mm, grading into phyllaries. Involucres campanulate to cylindric, (5–)7.5–10 mm. Phyllaries in 3–5(–6) series, outer ovate with expanded distal portion [(4–)5–6 mm], mid ovate-lanceolate [6–8(–10) mm] with expanded green portions, inner linear, unequal or sometimes subequal, outer often foliaceous, bases (mid) scarious, margins silky, green zones restricted to expanded distal 1 / 2 – 2 / 3 (obscured by hairs), apices (outer) spreading or squarrose to reflexed, acute, mucronulate, faces densely long-silky. Ray florets (10–)15–30; corollas usually rose-purple to deep purple, rarely white, laminae 8.5–11 × 1–1.5 mm. Disc florets (15–)25–35; corollas pink turning purple, (5–)5.5–7 mm, tubes shorter than narrowly funnelform throats (both thinly puberulent), lobes deltate, 0.7–0.9 mm. Cypselae purple or brown, obovoid, not compressed, 2–3 mm, 7–10-nerved (prominent), faces glabrous; pappi whitish or tawny, 6–7 mm. 2n = 10, 20.
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Diagnostic Description

Synonym

Aster sericeus Ventenat, Descr. Pl. Nouv., plate 33. 1800; Lasallea sericea (Ventenat) Greene; Virgulus sericeus (Ventenat) Reveal & Keener
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Ecology

Habitat

Range and Habitat in Illinois

The native Silky Aster occurs primarily in the northern tier of counties and in many counties along the Illinois and Mississippi Rivers (see Distribution Map). It is an uncommon plant that appears to be declining in abundance as a result of habitat destruction. These habitats include upland dolomite prairies, gravel prairies, sand prairies, hill prairies, stabilized sand dunes, upland sandy savannas, limestone glades, and prairie remnants along railroads. This is an indicator plant of high quality habitats in dry open areas. Faunal Associations
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Associations

Flower-Visiting Insects of Silky Aster in Illinois

Aster sericeus (Silky Aster)
(Bees suck nectar or collect pollen, flies suck nectar or feed on pollen, other insects suck nectar; most observations are from Reed, otherwise they are from Swengel & Swengel as indicated below)

Bees (long-tongued)
Apidae (Bombini): Bombus affinis, Bombus impatiens, Bombus vagans; Anthophoridae (Eucerini): Melissodes dentiventris; Megachilidae (Coelioxini): Coelioxys rufitarsis; Megachilidae (Megachilini): Megachile latimanus, Megachile relativa

Bees (short-tongued)
Halictidae (Halictinae): Agapostemon sericea, Agapostemon texanus texanus, Lasioglossum leucozonia

Wasps
Ichneumonidae: Exetastes angustoralis

Flies
Syrphidae: Eristalis dimidiatus, Eristalis stipator, Helophilus latifrons, Helophilus stipatus, Syrphus sp.; Bombyliidae: Systoechus sp.

Butterflies
Pieridae: Colias sp.; Lycaenidae: Lycaeides melissa samuelis (Sw)

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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: N2 - Imperiled

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread from Texas through the midwestern United States north to Canada (Kartesz 1999). Symphyotrichum sericeum is found in prairies, fields, and open rocky calcareous soils (Correll and Johnston 1970, Van Bruggen 1976, Voss 1996). It is frequent in the Great Plains of the United States and only becomes rare in the northern and eastern portion of its range.

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Wikipedia

Symphyotrichum sericeum

Symphyotrichum sericeum is a species of flowering plant in the aster family known by several common names, including western silver aster and silky aster. It is native to the central plains of North America.

Contents

Distribution[edit]

Symphyotrichum sericeum is an aster of rocky prairies, wood glades, and gravel hill prairies. It ranges from the eastern tall grass prairies and west in the short grass Great Plains to the foothills of the Rocky Mountains of the from Texas and New Mexico into the central grasslands in Canada. Its occurrence is rare in the northeast part of its range. It is seldom found outside its preferred habitat.

Description[edit]

The Symphyotrichum sericeum plant is distinctive in the wild due to the silky texture; no other American aster is sericeous throughout. This is a perennial herb growing from rhizomes. The stem is erect, sometimes branching. It is sericeous (silky) throughout, giving the stem a silvery-grey appearance. Basal leaves are oblanceolate in shape and have petioles. Cauline leaves, those growing along the stem, are ovate to ovate-lanceolate in shape, with alternate attachment to stem, sessile, acuminate at the base, acute at the tip. Leaf margins are entire, or smooth and lacking teeth or serration. Leaf texture is sericeous adaxally (above) and abaxally (below), giving the leaves a silvery-grey appearance.

Compared to other American asters, the flowers appear disproportionately large for the plant's size. The inflorescence is terminal, occurring at the top of the stem, and consists of a single head. The involucre is ovate to lanceolate in shape and sericeous. Ray flowers are blue and fertile. Disc flowers are white, with stamens yellow to brown. The fruit is an achene.

Conservation[edit]

Symphyotrichum sericeum is listed as a rare species in Indiana, and as a threatened species in Michigan.

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Notes

Comments

Symphyotrichum sericeum is known in the Bahamas as S. lucayanum (Britton) G. L. Nesom [syn. Aster lucayanus Britton, Virgulus lucayanus (Britton) Reveal & Keener]. It is of conservation concern in Indiana, Michigan, and Canada. Symphyotrichum sericeum is distinct and unlikely to be confused with other species due to its silvery-silky leaves and phyllaries, open arrays, and cormoid rootstocks. Aster sericeus forma albiligulatus Fassett is a white form of the species, in contrast to the typically purple forma sericeus; these do not deserve formal recognition.
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Names and Taxonomy

Taxonomy

Comments: Excludes plants sometimes known as Aster sericeus var. microphyllus; these are considered as a distinct species, Symphyotrichum pratense.

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