Eriogonum thymoides |
Eriogonum effusum |
|
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thyme buckwheat, thyme wild buckwheat, thyme-leaf buckwheat, thyme-leaf wild buckwheat |
spreading buckwheat, spreading wild buckwheat |
|
Habit | Subshrubs, spreading, polygamodioecious, 0.5–2(–3) × 1–3(–4) dm, tomentose to sericeous. | Shrubs, spreading, not scapose, (1.5–)2–5(–7) × 5–15 dm, grayish- to reddish-brown-tomentose to floccose and gray or, rarely, thinly floccose and greenish. |
Stems | caudex spreading; aerial flowering stems erect, slender, solid, not fistulose, arising at nodes of caudex branches and at distal nodes of short, nonflowering aerial branches, (0.1–)0.3–0.8(–1.2) dm, tomentose to sericeous, with a whorl of 6–10(–12), leaflike bracts ca. midlength, these similar to leaf blades, 0.3–0.8(–1) × 0.1–0.2 cm. |
spreading to erect, typically without persistent leaf bases, up to 1/2 height of plant; caudex stems absent; aerial flowering stems erect to spreading, slender, solid, not fistulose, 0.3–0.8 dm, floccose or glabrous. |
Leaves | in compact basal rosettes, fasciculate, and sheathing up stems; petiole 0.05–0.2 cm; blade linear to narrowly spatulate, (0.2–)0.3–1(–1.5) × 0.1–0.2(–0.3) cm, densely white-tomentose abaxially, silky-villous or sericeous adaxially, margins entire, inrolled to tightly revolute. |
cauline, 1 per node; petiole 0.2–0.7 cm, tomentose to floccose; blade oblanceolate to oblong or obovate, (1–)1.5–3 × (0.2–)0.3–0.7 cm, densely white-tomentose abaxially, white-floccose to glabrate or green and glabrous adaxially, margins plane. |
Inflorescences | capitate, 0.8–2 cm wide; branches absent; bracts absent immediately below involucre. |
cymose, 10–30(–40) × 10–40 cm; branches dichotomous, white-floccose to glabrate or subglabrous; bracts 3, scalelike, triangular, 0.5–2(–5) mm. |
Peduncles | absent or mostly erect, slender, 0.3–2.5 cm, floccose. |
|
Involucres | 1 per node, turbinate, 3–5 × 2.5–4 mm, villous to sericeous; teeth 6–8, erect, 0.5–1 mm. |
1 per node, turbinate, 1.5–2.5(–3) × 1–2 mm, tomentose to floccose; teeth 5, erect, 0.3–0.6 mm. |
Flowers | 4–10 mm, including 0.5–1 mm stipelike base; perianth white to pale yellow or yellow, becoming pink to rose, villous abaxially; tepals monomorphic, obovate; stamens included to slightly exserted, 2–4 mm; filaments pilose proximally. |
2–4 mm; perianth yellow, glabrous; tepals connate proximal 1/4, essentially monomorphic, elliptic to obovate; stamens mostly exserted, 2–4.5 mm; filaments sparsely pilose proximally. |
Achenes | light brown, 2–2.5 mm, glabrous except for densely pubescent beak. |
brown, 2–2.5 mm, glabrous. |
Eriogonum thymoides |
Eriogonum effusum |
|
Phenology | Flowering Apr–Jul. | Flowering Jun–Sep. |
Habitat | Sandy to gravelly, often volcanic flats, slopes, and outcrops, mixed grassland and sagebrush communities, montane conifer woodlands | Sandy to rocky slopes and flats, mixed grassland and sagebrush communities, juniper and montane conifer woodlands |
Elevation | (200-)600-1700 m ((700-)2000-5600 ft) | 1200-2500 m (3900-8200 ft) |
Distribution |
ID; OR; WA
|
CO; MT; NE; NM; SD; WY
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Discussion | Eriogonum thymoides is an exquisite species concentrated in three regions of the Pacific Northwest. The first is along the eastern edge of the Cascade Range from near Wenatchee, Washington (Adams, Benton, Chelan, Douglas, Franklin, Grant, Kittitas, Klickitat, Lincoln, and Yakima counties), to near the Dalles in extreme north-central Oregon (Union County). The second is from Baker and northern Malheur counties, Oregon, to Adams, Canyon, and Washington counties, Idaho. A third series of populations is in the Mount Bennett Hills area of Gooding County, Idaho, and just over the borders in Blaine, Camas, Elmore, and Lincoln counties. Staminate plants tend to have yellow flowers that quickly fade after pollen release. Pistillate plants tend to have white to pale yellow flowers that persist and greatly elongate as the achene matures. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Eriogonum effusum is rather common on the northern Great Plains and along the eastern slope of the Rocky Mountains in central and eastern Colorado, southeastern Montana, western Nebraska, northern New Mexico, southwestern South Dakota, and southeastern Wyoming. Some specimens from Chaffee County, Colorado, are thinly floccose and greenish (Atwood & Welsh 29689, BRY) and thus similar to E. leptocladon. A collection from Pyramid Lake, Washoe County, Nevada (Frandsen & Brown 182, NESH) is clearly mislabeled. A roadside collection of E. effusum gathered near Little America, Sweetwater County, Wyoming, in 1961 (G. Mason 4025, ASU) was an introduction that has not persisted. The spreading wild buckwheat is occasionally merged with Eriogonum microthecum even though the two are morphologically distinct and their ranges do not overlap. Plants in New Mexico are sometimes difficult to distinguish from the related E. leptocladon var. ramosissimum. The species is the food plant for the Rita dotted-blue butterfly (Euphilotes rita). A hybrid between Eriogonum effusum and E. pauciflorum has been named E. ×nebraskense Rydberg [E. multiceps Nees subsp. nebraskense (Rydberg) S. Stokes; E. pauciflorum Pursh var. nebraskense (Rydberg) Reveal]. The hybrid is known from Weld County, Colorado; Cheyenne and Kimball counties, Nebraska; and Converse and Platte counties, Wyoming. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 5, p. 360. | FNA vol. 5, p. 248. |
Parent taxa | Polygonaceae > subfam. Eriogonoideae > Eriogonum > subg. Oligogonum | Polygonaceae > subfam. Eriogonoideae > Eriogonum > subg. Eucycla |
Sibling taxa | ||
Synonyms | E. sphaerocephalum subsp. minimum, E. thymoides subsp. congestum | E. microthecum var. effusum |
Name authority | Bentham: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 14: 9. (1856) | Nuttall: Proc. Acad. Nat. Sci. Philadelphia 4: 15. (1848) |
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