Epilobium coloratum Biehler

Purple-Leaved Willow Herb

© SRTurner

Family - Onagraceae

Habit - Perennial forb, sometimes with rhizomes or stolons, often robust and rank.

Stems - To +1m tall, erect, herbaceous, terete to 4-angled with rounded angles, sub-hollow, glabrous or with thin vertical lines of antrorse curled hairs, single from the base, widely branching in apical half, often reddish at nodes.

	Stem.
© DETenaglia

Leaves - Stem leaves opposite, short-petiolate. Petioles to 1cm long, with a few strigose hairs on the margins. Blades glabrous, lanceolate, serrate, with antrorse strigose hairs on the margins. Midrib and lateral veins impressed adaxially, expressed abaxially, to +/-10cm long, 2cm broad, typically rounded at the base.

	Leaf adaxial.
© SRTurner

	Leaves abaxial.
© SRTurner

	Pressed leaf.
© DETenaglia

Inflorescence - Terminal bracteate panicles. Bracts foliaceous, reduced upward. Branches of inflorescence alternate, straight and antrorse-curled pubescent. Pedicels pubescent like the branches of inflorescence, to 3-4mm long in flower, elongating in fruit to 1cm long.

	Inflorescence.
© SRTurner

Flowers - Petals 4, white to pinkish, 3-5mm long, 2-3mm broad, glabrous, 2-lobed at apex, obovate to elliptic, distinct. Stamens 8, 4 being longer than the others, alternating with the petals, erect. Filaments to 2mm long, white, glabrous. Anthers pink, .2-.3mm in diameter. Stigma capitate, 1mm long, pale yellow. Style 1.5mm long, thicker than the filaments, glabrous. Calyx 4-lobed. Calyx tube to 1mm long. Lobes to 2-3mm long, 1-1.5mm broad, acute to acuminate or apiculate, entire, pubescent (curled and straight) externally, glabrous internally. Calyx tube with a few hairs internally. Ovary inferior, 6-13mm long in flower, antrorse and straight pubescent, 1mm broad, 4-angled (the angles rounded). Ovules many. Fruits to 6cm long, 1.3mm broad. Seeds to 2mm long, .5mm broad, brown, comose. The hairs to 1cm long, whitish brown to cinnamon.

	Flower.
© DETenaglia

	Calyx.
© DETenaglia

	Developing fruit.
© DETenaglia

Flowering - July - October.

Habitat - Wet ground.

Origin - Native to the U.S.

Lookalikes - Other species of Epilobium, particularly E. ciliatum. These can be difficult to distinguish.

Other info. - This species is found in scattered locations throughout much of Missouri. Its range includes the northeastern quadrant of the continental U.S. and also much of eastern Canada. The plant is easy to ID as a species of Epilobium from its habitat, opposite stem leaves and small whitish-pink flowers with elongate inferior ovaries. Differentiation from other species of Epilobium is more difficult, and relies on subtle and variable features of leaf and seed morphology. Of the three species of Epilobium which have been reported from Missouri, E. coloratum is by far the most frequent.

Photographs taken in Brown Summit, NC., 9-20-02 (DETenaglia); also at Weldon Spring Conservation Area, St. Charles County, MO, 8-14-2014, and Indian Camp Creek Park, St. Charles County, MO, 9-7-2015 (SRTurner).