Robinia neomexicana
Pl. Nov. Thurb., 314. 1854. (as neo-mexicana)
Shrubs or trees, 1–5(–15) m; branches tomentose to sericeous, eglandular. Leaves 10–25 cm; stipules 8–11 mm; petiole 0.5–1.6 cm, tomentose to sericeous; axis tomentose to sericeous, eglandular; petiolules 2–3 mm, tomentose to sericeous; leaflets 13–23, blades elliptic, 25–35 × 15–20 mm, surfaces strigose to sericeous. Racemes 10–20-flowered, lax to erect, 3–10 cm, rachis tomentose to sericeous or hispid, sometimes with stipitate glands; bracts lanceolate, 9–12 × 2–3 mm, margins entire. Pedicels 3–5 mm. Flowers: calyx tube 6–7 mm, tomentose to sericeous, sometimes with stipitate glands, lobes 5–7 mm; corolla pinkish, 20–25 mm. Legumes light to dark brown, 4–8 × 0.9–1.1 cm, hispid. Seeds 4–10(–15).
Phenology: Flowering spring–early summer.
Habitat: Open, disturbed settings, exposed rocky outcrops, steep slopes, pine forests and woodlands.
Elevation: 1500–2000 m.
Distribution
B.C., Ariz., Calif., Colo., Nev., N.Mex., Tex., Utah, Wyo., Mexico (Chihuahua, Sonora).
Discussion
Robinia neomexicana is native in the United States and Mexico, and is introduced in British Columbia.
The tomentose to sericeous leaf axes and branches, often stipitate-glandular inflorescence rachises, often conspicuously hispid fruits, and distribution in southwestern United States and adjacent Mexico distinguish Robinia neomexicana from other pink-petaled Robinia species. Forms of R. neomexicana without the hispid indument and glandular hairs on the inflorescence rachises and fruits retain the relatively abundant tomentose to sericeous indument on the leaves and branches.
D. Isely and F. J. Peabody (1984) and Isely (1998) recognized two weakly differentiated and largely sympatric varieties of Robinia neomexicana: var. neomexicana with ovaries and fruits sparsely hispid to strongly glandular-hispid and var. rusbyi with ovaries and fruits glabrous at maturity.
Nothospecies based on putative hybrids involving Robinia neomexicana and R. pseudoacacia, R. × holdtii Beissner and R. × coloradensis Dode, are found in the range of R. neomexicana where R. pseudoacacia has been planted.
Selected References
None.