Orobanche uniflora subsp. uniflora
Plants simple, rarely few-branched basally, often forked medially, (including pedicels) (4–) 7–18 (–25) cm, stems and inflorescence axes only 1–5 (–7) cm. Leaves and bracts usually 3–7 per stem or branch. Pedicels (8–) 30–110 (–170) mm. Calyx lobes narrowly to broadly lanceolate-triangular, 4–12 (–15) mm, slightly shorter than to only slightly longer than tube, narrowed relatively evenly from base to tip. Corollas white to pale-yellow, sometimes pale purplish tinged and/or with light purple veins, (11–) 15–25 (–30) mm, throat 2–4 mm diam., palatal folds slender, elongate; limb 3–6 (–9) mm. 2n = 36, 72.
Phenology: Flowering Apr–Jul.
Habitat: Old fields, upland hardwood forests, woodlands, thickets, hardwood hammocks, glades, bluffs, bogs, stream banks, riverbanks, gardens.
Elevation: 0–400(–2000) m.
Distribution
St. Pierre and Miquelon, B.C., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que., Alaska, Ark., Conn., Del., D.C., Fla., Ill., Ind., Iowa, Kans., Ky., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis., Mexico (Oaxaca)
Discussion
Subspecies uniflora, the widespread eastern subspecies, occurs as far west as the eastern edge of the Great Plains southward to eastern Texas, with disjunct populations in Alaska, British Columbia, and Montana. A single specimen parasitic on Baccharis (Camp 2451, NY) documents a major disjunct occurrence in Oaxaca, Mexico. The name Orobanche terrae-novae corresponds to a local race in Newfoundland with exceptionally deep corolla lobes bearing slightly shorter cilia.
Many specimens lack information on plants being parasitized or evidence of haustorial connections. The primary hosts of subsp. uniflora in temperate North America are perennial members of the Asteraceae, especially selected species of Eurybia, Rudbeckia, Solidago, Symphyotrichum, and rarely Hypochaeris. However, occasional and likely spurious host records are Betula and Ostrya (Betulaceae), Rhododendron (Ericaceae), Quercus (Fagaceae), and Potentilla (Rosaceae).
Selected References
None.