Coreopsis tripteris L.
Family - Asteraceae
Stems - To 2m tall, from a short woody caudex and thickened roots, herbaceous, erect, glabrous, glaucous, branching in apical 1/2, fistulose, single from the base.
Leaves - Opposite, decussate, petiolate, trifoliolate. Petioles glabrous, to 2cm long. Bases of opposing petioles connected and enveloping the stem. Lateral leaflets sessile. Terminal leaflet with a short petiolule (to 5mm long). Leaflets entire, pubescent abaxially, very sparse pubescent adaxially, acute, oblong-lanceolate to lanceolate, to 11cm long, 3.5cm broad. Venation is tuberculate adaxially and plainly visible below. Margins thickened and antrorse strigillose.
Inflorescence - A flat-topped cymose arrangement of flower heads.
Involucre - Biseriate, to 6mm tall (long), 7mm in diameter. Outer phyllaries green and linear, +/-6 in number, very sparse pubescent, +/-5mm long, 1mm broad, rounded at apex. Inner phyllaries broad, green at base, yellow in apical 1/2, pubescent externally, glabrous internally, the apices bent and spreading outward, acute, 7-8mm long, 3-4mm broad.
Ray flowers - Sterile, typically 8 per flower head. Ligules yellow, to +/-3cm long, to 1cm broad, glabrous or with very few hairs near base by the corolla tube. Achene compressed, to 3.5mm long in flower, yellowish, mostly glabrous but with some pubescence at apex. Pappus of short eros scales.
Disk flowers - Disk to -1cm broad. Corolla 5mm long, contracted at base for about 1mm, dark purple at apex, 5-lobed. LObes acute, triangular, spreading to recurved, +/-.8mm long. Stamens 5, adnate at apex of contracted portion of corolla tube. Filaments white, glabrous, compressed, 2.1mm long, with an obvious midvein. Anthers purple, to 2.3mm long, connate around the style, partially exserted. Style glabrous, pale yellow, slightly swollen at base, bifurcate, purple in apical portion (stigmas). Achenes compressed, greenish-white in flower, glabrous, 3mm long. Pappus of short eros scales. Receptacle flat. Chaff thin, glabrous, golden at the apex, 7-8mm long, .3mm broad.
Flowering - July - September.
Habitat - Prairies, rocky open woods, bluffs, thickets, roadsides, railroads.
Origin - Native to U.S.
Other info. - This tall species of Coreopsis is found throughout Missouri except in a few counties in the "bootheel." The plant is tolerant of dry conditions and would make a good garden specimen. This plant is easy to ID in the field because of its glabrous, glaucous stems and its trifoliolate leaves. Occasionally a small plant will have leaves which are undivided.
Photographs taken at Logan Creek, Reynolds County, MO., 7-17-03.