Robinia pseudoacacia
Robinia neomexicana
black locust, false acacia
desert locust, New Mexico locust
20–30 cm;
stipules 5–10 mm;
petiole 0.7–2.5 cm, strigose;
petiolules 2–3 mm, glabrate;
leaflets (7–)15–19, blades elliptic, 25–45(–65) × 10–20(–25) mm, surfaces glabrate.
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.
(10–)15–25-flowered, pendent, 5–19 cm, rachis sericeous;
bracts lanceolate, 8–10 × 1 mm, margins entire.
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.
7–12 mm.
3–5 mm.
calyx tube 5–6 mm, sericeous, lobes 1–2 mm;
corolla usually whitish, rarely pinkish, 15–20 mm.
calyx tube 6–7 mm, tomentose to sericeous, sometimes with stipitate glands, lobes 5–7 mm;
corolla pinkish, 20–25 mm.
light to dark brownish, 4–10 × 1–1.5 cm, placental margin narrowly winged, glabrous.
light to dark brown, 4–8 × 0.9–1.1 cm, hispid.
4–8(–16).
4–10(–15).
Robinia pseudoacacia
Robinia neomexicana
Robinia pseudoacacia is native at least in the Appalachian and other mountainous regions of eastern North America; it is widely cultivated and escaped throughout North America and other temperate regions of the world. Black locust can be highly invasive and is considered a threat to native biodiversity in many areas (J. Heim 1990; B. M. Farris 2007; L. Derickx and P. M. Antunes 2013). Populations growing at latitudinal extremes (such as Canada) are sometimes more likely to be shorter (3 m or less).
The report of Robinia pseudoacacia from Prince Edward Island is based on a single old specimen, and the species is here excluded from that province.
The winged and glabrous fruits and flowers with white petals arranged on pendent racemes set Robinia pseudoacacia apart from other species of the genus.
Nothospecies based on putative hybrids involving Robinia pseudoacacia and R. neomexicana (R. × holdtii Beissner, R. × coloradensis Dode) are found in areas where the former has been planted; those involving R. pseudoacacia and R. viscosa (R. × ambigua Poiret) are found in western North Carolina.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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