Cuscuta attenuata Waterfall, Rhodora 73: 575. 1972

Flowers: clusters dense. Calyces 1.5–3 mm, longer than corolla tube, divided 2/3 length, lobes ovate-lanceolate to narrowly lanceolate, bases not overlapping, apex acute-attenuate. 2n = 30.

Flowering late Aug–Oct. Hosts: usually Iva annua, rarely Symphyotrichum; of conservation concern; 0–400 m; Kans., Okla., Tex.

Variety attenuata resembles var. longisepala but is maintained as a separate variety of Cuscuta indecora because of its apparent host specialization and repro­ductive isolation (L. A. Prather and R. J. Tyrl 1993).