Orobanche minor
Orobanche fasciculata
clover broomrape, common broomrape, hellroot, lesser broom-rape
cluster broomrape
usually conspicuous (often forming a globular mass), very slender, usually branched.
inconspicuous, slender or stout, unbranched or few-branched.
several to numerous, loosely ascending to spreading, imbricate only near stem base;
blade lanceolate to oblong-ovate or triangular-ovate, 6–20 mm, margins entire, apex acute to acuminate, surfaces moderately to densely glandular-pubescent.
few to several, erect or reflexed;
blade oblong-ovate to ovate-triangular or awl-shaped, (4–)6–12(–15) mm, margins entire, apex acute or acuminate, surfaces glandular-pubescent distally.
spikes, reddish brown to purple or yellow, simple, sparsely to densely glandular-pubescent;
flowers numerous, axis visible between flowers;
bracts slightly reflexed, narrowly lanceolate, 6–17 mm, apex attenuate, glandular-pubescent.
fascicles, irregular corymbs, or short racemes of (1–)6–15(–20) flowers at stem or branch tips, light yellow to yellow or tinged pinkish to reddish purple, simple, densely glandular-pubescent, sometimes glabrescent proximally;
bracts erect or ± spreading, oblanceolate to oblong, lanceolate, or awl-shaped, sometimes ovate, 7–12 mm, apex acute, sometimes acuminate, moderately to densely glandular-pubescent.
0–0.8 mm (rarely to 30 mm in proximalmost flowers);
bracteoles 0.
10–70(–150) mm, proximal as long as or ± longer than plant axis, distal sometimes shorter;
bracteoles 0.
calyx yellow or brownish red to brownish purple, strongly bilaterally symmetric, (6–)8–12 mm, deeply divided into 2 lateral lobes (rarely with an additional vestigial abaxial lobe), lobes entire or asymmetrically divided into 2 teeth or short lobes, these much shorter than tube, lanceolate to subulate-attenuate, ± glandular-villous;
corolla 10–19 mm, tube white to pale yellow, not or only slightly constricted above ovary, ± curved, glandular-puberulent;
palatal folds prominent, yellow to nearly white, usually glabrous;
lips similar in color to tube, more commonly purplish tinged and/or veined, sometimes more strongly so externally, abaxial lip spreading abruptly from base, 3–4 mm, lobes broadly ovate to ± semiorbiculate (this sometimes difficult to observe because of the crinkled, erose-crenulate margins and overlapping sinuses), apex rounded or shallowly emarginate, adaxial lip erect or curved outward at tip, 3–5 mm, lobes shallow, ± semiorbiculate, apex broadly rounded;
filaments sparsely pubescent, distal hairs gland-tipped, anthers included, glabrous or tomentulose.
calyx light yellow to orangish yellow, tan, or grayish tan, often purplish tinged distally, sometimes entirely pinkish purple to reddish purple or dark purple, ± radially symmetric, (4–)6–12(–18) mm, divided into 5 subequal lobes, lobes shorter than to slightly longer than tube, triangular to subulate-triangular, moderately to densely glandular-pubescent;
corolla (11–)14–30(–38) mm, tube white to cream or yellow, purplish tinged, or pinkish purple to reddish purple, sometimes with darker pink, purple, or brown veins, slightly to moderately constricted above ovary, ± bent forward, glabrate or glandular-pubescent;
palatal folds ± prominent, usually yellow, moderately to densely glandular-pubescent;
lips yellow or pinkish purple to reddish purple, rarely white, sometimes with darker purple veins, abaxial lip ± spreading, 3–6(–9) mm, lobes oblong-obovate to nearly round, sometimes oblong-elliptic, apex rounded or ± pointed, sometimes shallowly emarginate, adaxial lip slightly to moderately spreading or recurved, (2–)3–6(–9) mm, lobes oblong-ovate to nearly round, sometimes oblong-elliptic, apex rounded or ± pointed;
filaments glabrous, anthers included, glabrous or villous-tomentose.
ovoid to oblong-ovoid, 5–9 mm.
ovoid to oblong-ovoid, 6–12 mm.
0.2–0.4 mm.
0.2–0.5 mm.
= 38.
= 48.
Orobanche minor
Orobanche fasciculata
Orobanche minor has been documented most frequently parasitizing introduced clovers (mainly Trifolium arvense and T. repens), and collected rarely on Crotalaria (J. W. Thieret 1971) and Vicia. It also has been recorded, at least historically, on a variety of cultivated hosts in the region, including hemp, carrots (Daucus carota), tobacco, geraniums (Pelargonium spp.), and Petunia spp. Allegedly, the species is toxic to livestock (Thieret). The sole specimen from Idaho (J. A. Allen s.n., 1875, NY) lacks locality data; if the provenance is correct, the elevational range would be extended upward.
European authors have recognized a number of infrataxa and segregates; for example, F. J. Rumsey and S. L. Jury (1991) provisionally accepted four varieties of Orobanche minor as occurring in the British Isles. However, they noted that little is known about cytological and morphological variation within the complex. Thus, it seems inappropriate to apply an infraspecific classification to the North American plants.
A single historical specimen (J. C. Nelson 3337, 25 August 1920, GH) collected from ship’s ballast in the Linnton area of Portland, Oregon, is an unusually stout plant with apparently pale corollas and filaments relatively densely pubescent toward their bases. This plant may represent a record of Orobanche loricata Reichenbach, a European species that parasitizes mainly Picris and other Asteraceae, and does not affect any crop plants. However, specimen condition precludes definitive determination, and the label does not list a host species. Other materials from Oregon have the typical morphology of O. minor.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Similar to Orobanche uniflora, O. fasciculata forms a polymorphic complex that may involve cryptic species. However, unlike O. uniflora, infraspecific taxa in O. fasciculata lack strong correlations with morphology, geography, and host ranges; they are not recognized here. Previously, D. M. Achey (1933) separated the species into three varieties based mainly on plant color and flower size. In her unpublished thesis, K. C. Watson (1975) expanded this to four subspecies but circumscribed her taxa differently. Both authors noted morphological overlap among taxa.
Of particular interest is a series of populations from California and adjacent Oregon [always parasitic on Galium (Rubiaceae)] to which Watson applied the manuscript name "subsp. uniflorioides" and that, in many ways, are morphologically intermediate between Orobanche fasciculata and O. uniflora. Recently, A. E. L. Colwell et al. (2017) segregated these under the name Aphyllon epigalium Colwell & A. C. Schneider. They are distinctive in having typically two to four flowers per stem, usually cream to yellow corollas (sometimes tinged with pink or purple), including the palatal folds, and glandular (versus ciliolate) corolla margins. Colwell et al. went further in subdividing their new species into two subspecies, segregating plants with somewhat smaller, cream-colored corollas having at most slightly recurved lips as subsp. notocalifornicum A. C. Schneider & Colwell and retaining plants with somewhat larger, yellow corollas with spreading lobes as subsp. epigalium. This treatment is tentative, pending further research into the population genetics within the entire complex.
Most references suggest that Orobanche fasciculata uses a broad range of hosts. However, there are four main genera of host plants: Artemisia (Asteraceae), Phacelia (Hydrophyllaceae), Eriodictyon (Namaceae), and Eriogonum (Polygonaceae). As noted above, a morphologically distinctive set of populations parasitizes Galium. Other less commonly reported hosts include Ericameria and Eriophyllum (Asteraceae), Atriplex and Grayia (Chenopodiaceae), Convolvulus (Convolvulaceae), Arctostaphylos (Ericaceae), Mirabilis (Nyctaginaceae), Pinus (Pinaceae), grasses (Poaceae), Delphinium (Ranunculaceae), Adenostoma, Prunus, and Purshia (Rosaceae), and Vitis (Vitaceae). Some minor hosts are listed based only on specimen label data and require confirmation.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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