Verbesina alternifolia (L.) Britton ex Kearney

Yellow Ironweed


CC = 4
CW = -3
MOC = 76

© DETenaglia

Family - Asteraceae/Heliantheae

Habit - Perennial forb with fibrous, sometimes slightly fleshy roots and often stout rhizomes.

Stems - Ascending to erect, to 2.5 m, narrowly and sometimes incompletely winged, often only below the midpoint, sparsely to moderately pubescent with short, spreading hairs, especially toward the tip, sometimes glaucous.To 3m tall, herbaceous, erect, multiple from the base, branching, winged, glaucous. Wings to +2mm broad, antrorse strigose on the margins, sparse pubescent.

Verbesina_alternifolia_stem.jpg Upper stem.

© SRTurner

Verbesina_alternifolia_stem2.jpg Lower stem.

Presence and degree of winging is variable. Strong winging is often restricted to the lower stems.

© SRTurner

Leaves - Alternate, or the lowermost leaves sometimes opposite, rarely nearly all opposite, simple, mostly sessile, the base usually minutely to strongly decurrent below the attachment point as a pair of wings. Blades 6-25 cm long, lanceolate to ovate, tapered at the base, tapered to a usually sharply pointed tip, the margins coarsely to finely toothed or sometimes nearly entire, the upper surface strongly roughened with sparse to moderate, short, spreading, pustular-based hairs, the undersurface similarly hairy, but often somewhat less roughened to the touch. Venation of blade expressed abaxially.

Verbesina_alternifolia_leaves.jpg Stem and leaves.

© SRTurner

Verbesina_alternifolia_leaf1.jpg Leaf adaxial.

© SRTurner

Verbesina_alternifolia_leaf2.jpg Leaf abaxial.

© SRTurner

Inflorescence - Usually terminal panicles with 8-100 heads. Peduncles scabrous, antrorsely pubescent.

Verbesina_alternifolia_inflorescence.jpg Inflorescence.

© SRTurner

Heads - Involucre 10-14 mm in diameter, more or less saucer-shaped, with 8-12 bracts. Involucral bracts 3-8 mm long, linear to narrowly lanceolate or narrowly oblanceolate, spreading to reflexed at flowering, the outer surface moderately hairy. Chaffy bracts narrowly lanceolate to narrowly oblong-oblanceolate, sparsely to moderately hairy.

Verbesina_alternifolia_heads.jpg Flowering heads.

© SRTurner

Verbesina_alternifolia_involucre.jpg Involucre.

© DETenaglia

Florets - Ray florets 2-10, sterile, the corolla 10-25 mm long, drooping, yellow, glabrous, often apically notched. Disc florets 40-80, the corolla 3.5-4.5 mm long, yellow. Style bifurcate, with stigmas curling, slightly exserted. Pappus of the ray and disc florets similar (but that of the ray florets often slightly shorter and more flattened), of 2 slender awns 1.5-2.0 mm long, smooth or with fine, upward-pointed barbs, more or less persistent at fruiting.

Verbesina_alternifolia_florets.jpg Disk and ray florets. Note that disk florets point in many directions.

© SRTurner

Verbesina_alternifolia_disks.jpg Disk florets. Pince-nez look is characteristic of receptive disk stigmas.

© SRTurner

Fruits - Spreading in all directions at maturity, 4-5 mm long, the body usually oblanceolate to broadly obovate, usually relatively broadly winged, less commonly narrowly winged or wingless, the surface glabrous or sparsely to moderately pubescent with fine, slightly pustular-based hairs.

Verbesina_alternifolia_fruits.jpg Young fruiting head.

© SRTurner

Verbesina_alternifolia_fruits2.jpg Mature fruiting head.

© SRTurner

Verbesina_alternifolia_achenes.jpg Achenes.

© SRTurner

Flowering - August - October.

Habitat - Bottomlands, streambanks, sloughs, valleys and alluvial woods near streams, pastures, roadsides.

Origin - Native to U.S.

Lookalikes - Broadly, many other members of the family, but especially V. helianthoides and Rudbeckia laciniata. Potentially, V. occidentalis, a species not yet documented from Missouri.

Other info. - This tall and showy species can be found throughout Missouri and is quite common. Its range extends to a broad swatch across the eastern half of the continental U.S., though it is less common near the northern and southern extents of the country. The plant is easy to identify in the field because of its winged stems, drooping rays, and hemispherical disks. It has a strong preference for riparian corridors and can nearly always be found in the rich bottomlands adjacent to streams and rivers. It is easily grown from seed and makes a great addition to the native plant garden. The flowers attract a profusion of insects.

The common name "ironweed" apparently derives from the similarity of the foliage to that of other ironweeds (genus Vernonia). The flowering heads within these two genera are, however, utterly different. Another common name for Verbesina alternifolia is "wingstem," though this term is not uniquely applied to this species.

Photographs taken at the Current River Conservation Area, Reynolds County, MO., 8-10-01 (DETenaglia); also at Little Lost Creek Conservation Area, Warren County, MO, 9-6-2015, and along the Katy Trail southeast of Dutzow, Warren County, MO, 10-17-2019 (SRTurner).