Erechtites hieraciifolius (L.) Raf. ex DC.

Fireweed, Pilewort


CC = 1
CW = 5
MOC = 63

© SRTurner

Family - Asteraceae/Senecioneae

Habit - Taprooted annual forb.

Stems - Strongly ascending to erect, to 2.5 m, usually unbranched below the inflorescence, lined and/or angled, glabrous to moderately pubescent with more or less spreading hairs.

Erechtites_hieraciifolius_stem.jpg Stem and nodes.

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Leaves - Basal and alternate, reduced in size upward, glabrous to moderately hairy, at least on the undersurface. Basal and lowermost stem leaves mostly short-petiolate, the blades simple, 3-20 cm long, elliptic to narrowly ovate, tapered to a sharply pointed tip, occasionally irregularly and shallowly pinnately lobed, the base tapered to the petiole, the margins sharply toothed, the venation pinnate. Median and upper leaves narrower with progressively shorter petioles and usually deeper lobes, sometimes sessile and with clasping bases, the very uppermost leaves often narrowly elliptic-lanceolate.

Erechtites_hieraciifolius_leaves.jpg Stem and leaves.

© SRTurner

Erechtites_hieraciifolius_leaf1.jpg Leaf adaxial.

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Erechtites_hieraciifolius_leaf2.jpg Leaf abaxial.

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Erechtites_hieraciifolius_leaf2a.jpg Upper stem leaf (abaxial).

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Inflorescence - Terminal and axillary panicles from the uppermost leaves, elongate to rounded in profile.

Erechtites_hieraciifolius_inflorescence.jpg Inflorescence.

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Heads - Discoid, short- to long-stalked, mostly with 20-45 florets. Involucre 10-17 mm long, cylindrical above a somewhat swollen, disclike base, the bracts in 2 series, usually glabrous, the inner series of 9-15 bracts, these relatively flat dorsally and uniformly green; the outer series of 4-7 bracts, these minute, ascending, and incurved, uniformly green.

Erechtites_hieraciifolius_involucre.jpg Involucre with florets at anthesis.

© SRTurner


© SRTurner

Florets - Ray florets absent. Disk florets with corollas 7-13 mm long, pale cream-colored. Style branches with a stigmatic line along each inner margin.

Fruits - Achenes 2-3 mm long, more or less linear in outline, not flattened, 10-12-ribbed, glabrous, light brown.

Erechtites_hieraciifolius_dehiscing.jpg Dehiscent head.

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Erechtites_hieraciifolius_fruits2.jpg Fruits on receptacle.

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Erechtites_hieraciifolius_fruiting.jpg Fruiting plant.

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Erechtites_hieraciifolius_fruits.jpg Fruits.

The pappus has dropped off from most of these achenes. Scale is in mm (0.5 mm divisions).

© SRTurner

Flowering - July - November.

Habitat - Rocky open woods, eroded slopes, thickets, waste ground, disturbed sites, fields, roadsides, railroads.

Origin - Native to the U.S.

Lookalikes - Senecio vulgaris.

Other info. - This tall and easily identifiable species is common throughout Missouri and the eastern half of the continental U.S., also ranging into Canada, Mexico, and Central America. The plant is a pioneer, one of the first species to become established after a soil disturbance or fire. It is fast-growing and can reach a height of 3m, although it can also flower when quite small, especially if it is mowed or is growing in an area with poor soil.

Missouri plants are assignable to var. hieraciifolius. Other botanists classify it in the genus Senecio, as S. hieraciifolius. The species name has been spelled in at least three different ways, but the one shown here appears to be correct (at least at present). The common name of the plant, "fireweed" or "burnweed," refers to its habit of quickly colonizing burned areas. With time, it is usually displaced and out-competed by other species. Since "fireweed" is a common moniker which has been applied to numerous unrelated plants, some people prefer to use the common name "pilewort" for this species.

Natives used a tea made from the plant to treat many ailments including diarrhea, cystitis, and dropsy.

Photographs taken in Brown Summit, NC., 7-12-02 (DETenaglia); also near Labadie, Franklin County, MO, 09-29-2008, at Pickle Springs Natural Area, Ste. Genevieve County, MO, 09-19-2009, at LaBarque Creek Conservation Area, Jefferson County, MO, 9-24-2014, Tyson County Park, St. Louis County, MO, 08-31-2018, Riverfront Park, Washington, Franklin County, MO, 9-15-2018, Don Robinson State Park, Jefferson County, MO, 9-19-2021 (SRTurner).