Aster pilosus Willd. - Hairy Aster

Aster pilosus plant

Family - Asteraceae

Stems - Single or multiple from the base, from many long slightly thickened roots, with sterile leafy offshoots and erect fertile stems, branching, striate, hirsute to pilose, herbaceous, terete, to 1m tall. Hairs of the stem multicellular (use a lens to see), dense, to +2-3mm long, spreading.

Aster pilosus stemStem.

Leaves - Alternate. Basal leaves petiolate, spatulate, to 20cm long (with petiole). Petiole winged (the wings erect and creating an adaxial groove), pilose. Blades of the basal leaves coarse serrate, to +3.5cm broad, appressed pubescent above and below, acute, elliptic (narrowly). Margins antrorse ciliolate. Major veins of leaf parallel to the midrib. Cauline leaves reduced upward, becoming sessile, entire, narrowly elliptic to linear, ciliate at the base, with spreading pubescence abaxially, antrorse appressed pubescent adaxially.

Aster pilosus leavesBasal leaves.

Aster pilosus leavesCauline leaves.

Inflorescence - Paniculate arrangement of flower heads. Heads pedunculate. Peduncles to +1cm long, each subtended by a foliaceous bract, densely pilose. Stems in the inflorescence densely pilose.

Involucre - Cylindric, 5-6mm tall, 3-4mm in diameter. Phyllaries apically acuminate to attenuate, with green spreading apices (the very tip hardened, sharp, and translucent), subulate, translucent but with a green midrib and apex, 4-5mm long, 1mm broad, mostly glabrous internally and externally but with some glands externally near the apex. Apical margins minutely glandular serrate (use a lens to see).

Aster pilosus involucreInvolucre.

Ray flowers - +/-30 per flower head, fertile, pistillate. Ligules white, to 1cm long, 1-2mm broad, minutely notched at the apex (use a lens to see), glabrous. Corolla tube sparsely pubescent externally, glabrous internally. Style exserted, yellowish at the apex, bifurcate. Stigmas 1mm long.

Disk flowers - Disk 5-8mm broad. Corollas 4-5mm long, 5-lobed, glabrous internally and externally, yellowish in apical half, greenish basally. Lobes erect, acute, 1.1mm long, yellowish to reddish with age, glabrous. Stamens 5, exserted, adnate in middle of the corolla tube. Filaments thin, glabrous, white to yellowish. Anthers yellow, connate around the style, -2mm long. Style green basally, glabrous, exserted, purple and bifurcate apically. Receptacle flat and naked.

Aster pilosus flowers

Flowering - August - November.

Habitat - Dry soils of fallow fields, meadows, prairies, glades, rocky open ground, gravel bars, roadsides, railroads, waste ground, disturbed sites.

Origin - Native to U.S.

Other info. - This highly variable species is common and found throughout Missouri. It is one of the most common Asters in the eastern U.S.
The plant can have glabrous to hirsute stems and leaves and variably shaped leaves. Steyermark separates the species into 3 varieties and several forms based on pubescence and leaf shape. The plant described above is A. pilosus var. pilosus f. pilosus. A glabrous variety, var. demotus Blake is perhaps the most common variety in the state which can lead to confusion when trying to differentiate this species from other in the genus. The hardened, sharp apices of the involucre are a good characteristic for field identification.

Photographs taken in Brown Summit, NC., 10-3-02.


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