Eupatorium fistulosum Barratt - Joe-Pye Weed
Family - Asteraceae
Stems - To +2m tall, erect,
simple, herbaceous, hollow, solid purple to purplish-green with purple
mottling, glabrous, typically glaucous, from fibrous roots.
Leaves - In whorls of 4 to
5, petiolate. Petiole to +2cm long, glabrous. Blade to +25cm long, +8cm
broad, elliptic to elliptic lanceolate, serrate, acuminate, pubescent below.
Teeth of margins with minute prickle tip caused by vascular tissue extending
beyond leaf tissue.
Inflorescence - Flower heads
in terminal paniculate cyme to +30cm tall (long), +/-20cm broad. Branches
of inflorescence tomentoulose, reddish-purple. Flower heads with 5-6 flowers.
Involucre - 9mm long(tall),
2.5mm in diameter, greenish near base fading to pinkish-purple above. Phyllaries
imbricate. Outermost phyllaries tomentoulose. Inner phyllaries mostly glabrous
and with ciliolate margins.
Involucre.
Ray flowers - Absent.
Disk flowers - Flowers +/-5 per head. Corolla tube
to 3.1mm long, 5-lobed, pink to purplish, glabrous. Lobes acute, .9mm long,
glabrous. Stamens 5, adnate about 1/2 way up corolla tube, alternating
with corolla lobes. Filaments pinkish, glabrous. Anthers pinkish-purple,
1.1mm long. Style bifurcate. Stigmas to 3.5mm long, well exserted. Achenes
green in flower, 3mm long.
Flowers close-up.
Flowering - July - September.
Habitat - Moist ground, wet meadows, cultivated.
Origin - Native to U.S.
Other info. - This species
occurs naturally in only a few counties in Missouri. It is, however, widely
cultivated and can be found nearly throughout the state. The brilliant
purple stems and large inflorescences make it a desirable plant. This
species is often confused with E. purpureum L. but
the latter has more greenish stems, which are typically solid, and lighter
colored flowers.
Photographs taken off Hwy 40 near Knoxville, TN, 8-9-04.
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