Prodr. 15(2): 1073. 1866.
Herbs or subshrubs, 1–3 m. Roots thickened. Stems erect, terete when young; nodes not swollen; leaf and stipule-scars not elevated. Leaves: stipules lanceolate, entire; petiole 3–12 cm; blade basally attached, 5–7-lobed, lobes with acute secondary lobes proximally, median lobe 5–15 cm, margins neither thickened nor revolute, remotely serrate, apex acute, surfaces glabrous, abaxial smooth. Inflorescences axillary, racemes, to 12 cm. Pedicels: staminate 3–8 mm; pistillate 10–25 mm in fruit, downcurved. Staminate flowers: calyx campanulate, 10–18 mm, lobes erect or spreading; stamens 10. Capsules 1.5 cm, finely tuberculate, not winged. Seeds globose, 12 mm.
Phenology: Flowering Jul–Oct.
Habitat: Desert scrub, thorn scrub, oak woodlands, oak grasslands.
Elevation: 30–2000 m.
Ariz., Mexico (Baja California Sur), Mexico (Chihuahua), Mexico (Sinaloa), Mexico (Sonora)
D. J. Rogers and S. G. Appan (1973) noted the overall similarity and nearly identical geographic ranges of Manihot angustiloba and M. davisiae, yet they maintained these taxa as separate species, presumably because of their (nearly) constant and consistent differences in leaf lobe outline. Manihot angustiloba has generally narrow, nearly linear, primary lobes with a pair of serrate secondary lobes forming the widest portion of the lobe proximal to the middle; M. davisiae has generally broader leaf lobes with one pair of rounded secondary lobes that form the widest portion of the lobe distal to the middle, or two pairs of nearly equal, rounded, secondary lobes proximal and distal to the middle. Some specimens exhibit an intermediate condition: primary lobes that are narrow distally but also bear a pair of rounded secondary lobes proximal to the middle.
In the flora area, Manihot angustiloba is restricted to Cochise, Pima, and Santa Cruz counties.