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Erigeron oreganus

Gorge daisy, gorge fleabane, Oregon fleabane

Canadian fleabane, horseweed

Habit Plants perennial, 5–15 cm; taprooted, caudices unbranched. Plants 0.2–30+ dm.
Stems

decumbent to erect; hirsute with unequal hairs, sparsely glandular.

Leaves

2–10 cm;

margins entire or serrulate;

surfaces hispid to strigillose or scabrous, often glabrous with age.

Basal leaves

persistent, obovate, 15–90 × 5–20 mm;

margins coarsely serrate to shallowly lobulate;

surfaces sparsely to moderately hirsute to strigose.

Cauline leaves

obovate to elliptic; little or not reduced distally;

surfaces sparsely to moderately hirsute.

Peduncles

1–25 mm, glabrous to strigillose.

Involucres

4–7 × 9–15 mm.

3–4 mm.

Ray florets

30–60, pink to purple;

rays 4–5 × 0.5–1 mm.

Disc florets

corollas 3–5 mm.

Phyllaries

in 2–3 series, pale green with dark green medial stripe;

surfaces remotely hirsute, strongly stipitate-glandular.

tips acute;

surfaces glabrous or sparsely strigillose.

Fruits

2–3 mm, moderately strigose;

inner pappi of several unbarbed to weakly barbellate twisted bristles.

1–1.5 mm, tan to gray-brown, lightly strigillose;

pappus bristles 1.5–3 mm.

Heads

1–4, radiate.

Outer florets

20–45+;

corollas 2–3 mm;

rays 0.3–1 mm, white.

Inner florets

8–30+.

2n

=18.

Erigeron oreganus

Conyza canadensis

Distribution
[WildflowerSearch map]
[BONAP county map]
[BONAP county map]
Discussion

Shady cliffs, rocky slopes, crevices. Flowering May–Aug. 100–400 m. Casc. WA. Native.

This uncommon species is found only in the Columbia River Gorge.

Riverbanks, lake shores, woods, shrublands, clearcuts, roadsides, waste ground, disturbed areas. Flowering Jun–Sep. 0–2000 m. All ecoregions. CA, ID, NV, WA; nearly worldwide. Native.

Like many weedy species, C. canadensis is variable in size and habit depending on environmental conditions. It ranges from plants over 3 m tall to small, depauperate individuals only 2–3 cm. It is well separated from C. bonariensis by its smaller, more or less glabrous heads and shorter pappus bristles. Both species are able to reproduce through self-pollination (Noyes 2000).

Source Flora of Oregon, volume 2, page 259
James Riser, Stephen Meyers
Flora of Oregon, volume 2, page 231
Kenton Chambers
Sibling taxa
E. acris, E. aliceae, E. annuus, E. aphanactis, E. aureus, E. bloomeri, E. cascadensis, E. cervinus, E. chrysopsidis, E. compositus, E. corymbosus, E. coulteri, E. decumbens, E. disparipilus, E. divergens, E. eatonii, E. elegantulus, E. filifolius, E. foliosus, E. glacialis, E. glaucus, E. howellii, E. inornatus, E. karvinskianus, E. klamathensis, E. latus, E. linearis, E. lonchophyllus, E. nivalis, E. peregrinus, E. petrophilus, E. philadelphicus, E. poliospermus, E. pumilus, E. simplex, E. speciosus, E. stanselliae, E. strigosus, E. tener, E. vagus
C. bonariensis, C. canadensis
Synonyms Conyza canadensis var. canadensis, Conyza canadensis var. glabrata, Erigeron canadensis
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