Amphiachyris dracunculoides (DC.) T.&G. - Broom Snakeroot
Family - Asteraceae
Stems - To +60cm tall, erect, herbaceous, annual, from a taproot, typically single from the base and simple in the basal 1/2-2/3. Lower stem appearing woody, 3-5mm in diameter, grayish-brown. Stems in inflorescence divaricate, glabrous, green, angled or grooved.
Leaves - Mostly absent at anthesis. Leaves of the inflorescence linear, sessile, with punctate dots (use lens to see) and minute serrulate teeth on the leaf margins (use lens to see), +/-1mm broad, to 6cm long.
Inflorescence - Many small flower heads terminating each branch of the inflorescence. Stems spreading to +/-50cm broad at anthesis in a "mound" shape. Each flower head subtended by linear bracts giving way to the involucre.
Involucre - +/-2-3mm broad, 2-3mm tall, essentially biseriate. Lower series with green phyllaries. Phyllaries glabrous, linear-lanceolate, +/-2mm long, 1mm broad, acute. Inner series of phyllaries yellow-green (translucent at the base), glabrous, +3mm long, 1.5-1.8mm broad at the apex, acute, with the apical 1/4 spreading outward.
Ray flowers - +/-8 per flower head, spreading, pistillate and fertile. Ligule yellow, 3-4mm long, 2mm broad, elliptic-oblong, glabrous, with 2 impressed veins above (expressed below). Corolla tube 1-1.5mm long, whitish, glabrous. Style slightly exserted and bifurcate, whitish, .5-.6mm long, glabrous. Stigmas 1mm long, yellow, glabrous. Pappus absent or a minute, translucent crown.
Disk flowers - Disk +/-3mm broad, with +/-15 flowers. Flowers staminate. Corolla tube translucent-yellow, glabrous, 3mm long, 5-lobed. Lobes spreading, yellow, acute, +/-.5mm long, glabrous. Stamens 5, adnate at the base of the corolla tube. Filaments translucent, .7mm long. Anthers yellow, connivent around the undivided style, 1mm long, partially exserted. Style +2mm long, translucent in the basal 2/3, with the apical 1/3 pubescent and yellowish and exserted. Receptacle flat, naked but with ridges around the flower bases. Pappus a translucent awned crown. Awns equaling or exceeding the corolla. Crown (undivided portion) short, .3-.5mm long.
Flowering - July - October.
Habitat - Upland prairies, limestone and dolomite glades, bluff tops, riverbanks, fallow fields, disturbed sites, roadsides, railroads.
Origin - Native to U.S.
Other info. - This attractive little species can be found in the southwest corner of Missouri. Although it is not seen in the plant photo above, the plant nearly always grows from a single trunk-like base and then branches widely in the upper half (the whole plant being as wide or wider than tall). This species grows in profusion along roadsides in the Great Plains and is quite common there. It is far less abundant in Missouri.
Photographs taken at Tall Grass Prairie National Preserve, KS., 9-18-06.