Five-angled dodder

Cuscuta arvensis Beyrich ex Engelmann; C. pentagona var. microcalyx Engelmann; Grammica pentagona (Engelmann) W. A. Weber

Stems yellow to orange, slender to medium. Inflorescences dense, corymbiform to glomer­ulate; bracts at base of clusters 1, at base of pedicels 0 or 1, ovate or ovate-triangular to lanceolate, membranous, margins entire, apex acute. Pedicels 0.5–3(–4.5) mm. Flowers (4 or)5-merous, 1.4–2.5 mm, membranous, corolla lobes sometimes papillate; calyx yellow to brown, angled, cupulate, equaling corolla tube length, divided 1/2–2/3 its length, ± reticulate, shiny or not, lobes broadly ovate to rhombic, base auriculate, overlapping, forming prominent angles at sinuses, margins entire, midvein not carinate, without multicellular protuberances, apex rounded; corolla whitish, drying yellow to brown, 1.2–2.2 mm, tube campanulate, 0.7–1.2 mm, not saccate, lobes spreading, triangular-lanceolate, equaling corolla tube length, margins entire, apex acute to acuminate, inflexed; infra­staminal scales ovate to oblong, 0.7–1.4 mm, equaling or longer than corolla tube length, bridged at 0.3–0.5 mm, rounded, ± uniformly densely fimbriate, 0.15–0.25 mm; stamens exserted, shorter than corolla lobes; filaments 0.3–0.4 mm; anthers 0.2–0.3 × 0.2–0.3 mm; styles filiform, 0.7–1.1 mm, equaling ovary. Capsules depressed-globose to ovoid, 1.9–2.4 × 1.6–2.5 mm, not thickened or raised around relatively medium-sized to large interstylar aperture, translucent or not, base ± enveloped by withered corolla, indehiscent. Seeds 4, angled, subglobose to broadly ellipsoid, 0.9–1.1 × 0.8–1 mm, hilum region subterminal. 2n = 56.

Flowering Apr–Nov. Hosts: herbs; 0–900 m; Man.; Ala., Ark., Del., D.C., Fla., Ga., Ill., Ind., Kans., Md., Mass., Mich., Minn., Miss., Mo., Mont., N.J., N.Y., N.C., N.Dak., Okla., Pa., S.C., S.Dak., Tenn., Tex., Va.

Cuscuta pentagona apparently has not spread outside of North America, where it is less common than C. campestris. It is currently included in North American noxious weeds lists although there is no evidence it attacks crops.

G. Engelmann (1859) distinguished four varieties of Cuscuta pentagona: var. calycina, var. microcalyx, var. pentagona, and var. verrucosa (Engelmann) Yuncker. T. G. Yuncker (1932, 1965) treated var. calycina and var. verrucosa at specific rank and provided a new name for each: C. campestris and C. glabrior, respectively. Cuscuta glabrior is currently accepted by all the North American overviews; C. campestris has been persistently considered a synonym of C. pentagona despite morpho­logical and evolutionary evidence that the two are dis­tinct (M. Costea et al. 2006c, 2015).

Cuscuta pentagona differs from C. campestris in its rhombic to ovate, auriculate calyx lobes with over­lapping bases that form angles at sinuses and in its smaller flowers, capsules, and seeds.