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FNA | Family List | FNA Vol. 5 | Polygonaceae | Eriogonum

88. Eriogonum heermannii Durand & Hilgard in War Department [U.S.], Pacif. Railr. Rep. 5(3): 14. 1857. (as heermanni).

Eriogonum geniculatum Durand & Hilgard, J. Acad. Nat. Sci. Philadelphia, n. s. 3: 45. 1855, not Nuttall 1848

Shrubs and subshrubs, spreading to rounded and occasionally erect, not scapose, (0.5-)1-20 × 2-25 dm, glabrous or occasionally floccose, sometimes scabrellous, greenish, infrequently grayish. Stems spreading or erect, without persistent leaf bases, up to 2 height of plant; caudex stems absent; aerial flowering stems erect or nearly so, slender to stout, solid, not fistulose, 0.02-0.5 dm, thinly tomentose or glabrous.  Leaves cauline, 1 per node, quickly deciduous; petiole 0.1-1.5 cm, floccose or glabrous; blade linear, oblanceolate or spatulate or elliptic, or oblong, (0.4-)1-2(-4) × 0.1-0.8 cm, tomentose to floccose or glabrous abaxially, floccose to thinly floccose or glabrous adaxially, margins plane. Inflorescences cymose or racemose, 1-25(-30) × 1-30(-35) cm; branches dichotomous, sometimes with secondaries suppressed, smooth or angled to ridged and grooved, glabrous or occasionally floccose or scabrous; bracts 3, scalelike, 0.3-2 mm. Peduncles absent. Involucres 1 per node, narrowly turbinate or campanulate, 0.7-3 × 0.7-4 mm, glabrous, infrequently floccose; teeth 5, erect, 0.3-0.7 mm. Flowers (1.5-)2-4 mm; perianth white, yellowish white, pink, or reddish, glabrous; tepals connate proximal 4, dimorphic, those of outer whorl obovate to orbiculate, those of inner whorl narrowly lanceolate to oblong; stamens exserted, 2-5 mm; filaments pilose proximally. Achenes light brown to brown, 2-5 mm, glabrous.

Varieties 8 (8 in the flora): w United States.

As Eriogonum heermannii is here circumscribed, the number of varieties is dramatically decreased from past presentations, with E. apachense reduced to synonymy under a now greatly expanded var. argense. Also included in that variety is the more stoutly branched var. subracemosum. The southern var. heermannii of basically desert ranges and the more northern var. occidentale of the Coast Ranges in California are maintained, but their separation is more traditional than certain. The fragile and bulky nature of many dried, often poorly prepared specimens, and the tendency for leaves to fall away have made varietal identification within E. heermannii difficult.

Eriogonum heermannii varieties are food plants for Ellis's dotted-blue butterfly (Euphilotes ellisi) and the Mormon metalmark (Apodemia mormo mormo).

1 Flowering stems and inflorescence branches round or angled, scabrellous or papillate-scabrous; plants often densely branched   (2)
+ Flowering stems and inflorescence branches round, not angled, usually smooth, glabrous or thinly tomentose; plants sparsely branched   (3)
2 (1) Flowering stems and inflorescence branches round, usually distinctly scabrellous or in-frequently papillate-scabrous; Arizona, se California, Nevada   88g var. argense
+ Flowering stems and inflorescence branches sharply ridged and deeply grooved, minutely scabrellous; nw Arizona, se California, s Nevada, sw Utah   88h var. sulcatum
3 (1) Involucres not racemosely arranged on inflorescence branches, or only last 2-3 so disposed; inflorescences diffusely branched, glabrous; Great Basin or northeast edge of Mojave Desert   (4)
+ Involucres racemosely arranged along inflorescence branches or at least at tips of branches; inflorescences openly branched, glabrous or floccose to thinly tomentose; Mojave and Sonoran deserts   (5)
4 (3) Inflorescence branches mostly slender, smooth, not ridged, not spinose; inflorescences 3-15(-23) × 5-20 cm; subshrubs or shrubs, 3-7 × 5-12(-15) dm; Great Basin, ec California and Nevada   88a var. humilius
+ Inflorescence branches stoutish, faintly ridged and grooved, spinose; inflorescences 3-7(-10) × 3-10(-12) cm; shrubs, 1-3 × 1.5-5(-8) dm; Mojave Desert, sw Utah and nw Arizona   88b var. subspinosum
5 (3) Inflorescence branches thinly tomentose to floccose; s California, s Nevada, nw Arizona   88f var. floccosum
+ Inflorescence branches glabrous; s Nevada, California   (6)
6 (5) Involucres racemosely arranged; inflorescence branches whiplike; s Nevada   88c var. clokeyi
+ Involucres racemosely arranged only distally; inflorescence branches not whiplike; California   (7)
7 (6) Leaf blades 0.5-1.5 cm, glabrous abaxially; inflorescence branches stout; sc California   88d var. heermannii
+ Leaf blades 1.5-3(-4) cm, mostly tomentose to floccose abaxially (at least in early anthesis); inflorescence branches slender; sw California   88e var. occidentale


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