Aster azureus Lindl. - Blue Aster

Aster azureus plant

Family - Asteraceae

Stems - To 1m tall, glabrous to hispidulous, single from the base, typically simple in the lower 1/2, terete, erect, herbaceous.

Aster azureus stemHispidulous stem.

Leaves - Alternate. Basal leaves long petiolate, the petiole to +15cm long. Blades of basal leaves cordate to truncate or abruptly narrowed at base, very scabrous above and below, to 10cm long, 7cm wide. Middle and upper cauline leaves greatly reduced as compared to basal leaves, 2-10mm broad, sessile, appearing as linear bracts near inflorescence.

Aster azureus leavesBasal leaves.

Aster azureus leavesCauline leaves.

Inflorescence - Loosely paniculate, open, many flowered(+75) but the flowers opening at different times.

Involucre - 4.5-7mm tall (long), cylindric. Phyllaries imbricate, lanceolate, appressed, mostly whitish with distinct rhombic green tips, margins minutely ciliolate.

Aster azureus involucreInvolucre.

Ray flowers - Ligules blue, to 9mm long, typically +/- 15 per flower head.

Disk flowers - Disk 4-5mm broad. Corollas yellow, small, 15-30 per head. Achenes glabrous, +/-1mm long. Pappus of capillary bristles, +2.5mm long.

Aster azureus flowers

Flowering - September - October.

Habitat - Open woods, prairies, pastures, glades, roadsides.

Origin - Native to U.S.

Other info. - This little but showy species can be found scattered throughout much of Missouri. Steyermark wrote, however, that it is found in less than half the counties in the state.
The plant is easy to identify because of its leaves, which are very scabrous - almost like sandpaper. The small blue flowers and green diamond-tipped phyllaries help also. Plants with glabrous stems can be growing right next to those with hispidulous stems so stem pubescence is NOT a good character to use for identification.

Photographed in Eminence, MO., 9-21-03.


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