Erigeron disparipilus |
Erigeron tracyi |
|
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Snake River daisy, Snake River fleabane, white cushion fleabane |
running fleabane |
|
Habit | Perennials, 3–12 cm; taprooted, caudices branched. | Annuals, biennials, or short-lived perennials, 2.5–8(–12, 18) cm; usually taprooted, sometimes fibrous-rooted, caudices simple or branched. |
Stems | erect, densely pilose to hirsute or villoso-hirsute (hairs usually slightly ascending, loose, often mixed in orientations, of unequal lengths, relatively thin-based), eglandular. |
first erect (greenish proximally), then producing herbaceous, leafy, prostrate runners (stoloniform branches, sometimes with rooting plantlets at tips), densely hirsutulous (hairs spreading-deflexed, of relatively even lengths and orientations), sparsely minutely glandular. |
Leaves | mostly basal (persistent), (petioles prominently ciliate, hairs thick-based, spreading); blades linear to linear-oblanceolate, 20–40 × 1–2 mm, margins entire, faces finely hirsute, eglandular; cauline reduced, restricted to proximal 1/3 of stems. |
mostly basal (persistent in early season); blades oblanceolate to spatulate (obovate-elliptic laminae), 10–30(–60) × 3–6(–12) mm, cauline abruptly reduced distally, margins entire, dentate, or lobed, faces densely hirsute, eglandular. |
Involucres | 5–7 × 8–16 mm. |
3.5–4.5(–6) × 6–9(–12) mm. |
Ray florets | mostly 30–60; corollas usually white, sometimes fading pink, rarely blue, 5–10 mm, laminae loosely coiling. |
60–130; corollas white, often purplish abaxially, sometimes with an abaxial midstripe, 5–9 mm, laminae not coiling or reflexing. |
Disc corollas | 2.8–4 mm. |
2–3 mm (throats indurate and slightly inflated). |
Phyllaries | in 2–3 series, hirsute to hirsuto-strigose, minutely glandular. |
in 3–4 series, sparsely to moderately hirsute, minutely glandular. |
Heads | 1. |
1(–3 rarely, from midstem or proximal branches). |
Cypselae | 1.8–2.2 mm, 2-nerved, faces moderately, loosely strigose; pappi: outer of setae, inner of 15–25 bristles. |
0.7–1.3 mm, 2-nerved, faces sparsely strigose; pappi: outer of setae, inner of 12–16 bristles. |
2n | = 27. |
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Erigeron disparipilus |
Erigeron tracyi |
|
Phenology | Flowering May–Aug. | Flowering Mar–Oct. |
Habitat | Gravelly and rocky slopes, ridges, sagebrush, grassland | Desert scrub, grassy slopes, oak chaparral, pinyon-juniper woodlands, Douglas fir-ponderosa pine |
Elevation | 600–2000(–2200) m (2000–6600(–7200) ft) | 700–2300(–2400) m (2300–7500(–7900) ft) |
Distribution |
ID; OR; WA
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AZ; CO; KS; NM; NV; OK; TX; UT; Mexico (Baja California, Chihuahua, Coahuila, Durango, Sonora, Zacatecas)
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Discussion | Erigeron disparipilus is similar to E. nanus but less variable. The range of E. disparipilus barely contacts that of E. nanus in southeastern Idaho and they have different ecologies; blue rays of E. disparipilus in Owyhee County may indicate that hybridization occurs. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
In March through June, plants of Erigeron tracyi produce leaves in a basal rosette usually with a single, erect, monocephalous, stem. Stoloniform branches are soon formed (often recognized on pressed specimens by the leaves mostly on one side of the branches), and by the end of the season (August through October), prostrate runners are usually evident, sometimes forming terminal, rooting plantlets. Erigeron tracyi is similar in habit to E. flagellaris, particularly in the herbaceous stolons or stoloniform branches; the stem pubescence of E. tracyi is different, the stolons much less commonly produce rooting plantlets at the tips, and the plants tend to be perennial with woody or lignescent caudices, although they are variable both in habit and duration. Apparent hybrids with E. modestus and E. flagellaris are occasionally encountered, and the most common form of E. tracyi is perhaps (speculative) a stabilized, apomictic hybrid between the latter and E. divergens. All chromosome counts thus far have shown E. tracyi to be triploid and asynaptic. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 20, p. 285. | FNA vol. 20, p. 340. |
Parent taxa | Asteraceae > tribe Astereae > Erigeron | Asteraceae > tribe Astereae > Erigeron |
Sibling taxa | ||
Synonyms | E. cinereus, E. colomexicanus, E. commixtus, E. divergens var. cinereus | |
Name authority | Cronquist: Brittonia 6: 194. (1947) | Greene: Pittonia 5: 59. (1902) |
Web links |