Monographs Details: Lotus oroboides (Kunth) Ottley x L. wrightii (A.Gray) Greene
Authority: Isely, Duane. 1981. Leguminosae of the United States. III. Subfamily Papilionoideae: tribes Sophoreae, Podalyrieae, Loteae. Mem. New York Bot. Gard. 25 (3): 1-264.
Discussion:Several ambiguous specimens from northern Mohave, Coconino and Graham cos Arizona may be hybrid derivatives of Lotus oroboides and L. wrightii. The following (ARIZ) examples present different character combinations: Kearney & Peebles 12693, Mohave co. Mat-forming, as L. oroboides; leaves of L. wrightii; flowers solitary, shortly pedunculate to subsessile. Osborn 4343, Coconino co. Flexuous stems; relatively few leaves; broad leaflets; large flowers sessile. Griner s.n. Mohave co, south of Hackberry, 1949. Diffuse; long slender nodes; leaves pinnate or palmate; peduncles short, 1-2-flowered.
At the southern extremity of the range of Lotus wrightii, the L. wrightii phase 2 of this essay might in part represent hybrid derivatives between L. wrightii and L. oroboides var nanus. A specimen that distinctly suggests hybrid origin is Nelson & Nelson 1960, Mazatzal Mts, Arizona (RM); “Plants probably sprawling; leaves palmate or barely pinnate, mostly obovate; umbels 2-3 flowered; calyx lobes filiform.” This collection differs from L. wrightii phase 2 types primarily in having broader leaflets.