Robinia pseudoacacia
Robinia viscosa
black locust, false acacia
clammy 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.
10–20 cm;
stipules 3–6 mm;
petiole 0.7–2 cm, with sessile glands, sometimes glands stipitate;
axis glandular, glands usually sessile, sometimes stipitate;
petiolules 1–2 mm, glabrate;
leaflets 13–25, blades elliptic, 20–42 × 10–20 mm, surfaces sericeous abaxially, glabrate adaxially.
(10–)15–25-flowered, pendent, 5–19 cm, rachis sericeous;
bracts lanceolate, 8–10 × 1 mm, margins entire.
10–20-flowered, lax to ascending, 4–10 cm, rachis sericeous or hispid;
bracts oblanceolate to obovate, 10–15 × 3–5 mm, margins 1–several-toothed (when 1, then with long-attenuate central tooth).
7–12 mm.
3–6 mm.
calyx tube 5–6 mm, sericeous, lobes 1–2 mm;
corolla usually whitish, rarely pinkish, 15–20 mm.
calyx tube 4–5 mm, sericeous, lobes 4–5 mm;
corolla pinkish, 20–25 mm.
light to dark brownish, 4–10 × 1–1.5 cm, placental margin narrowly winged, glabrous.
rarely forming, dark brownish to purplish, 4–6 × 0.8–1 cm, glandular-hispid.
4–8(–16).
4–9.
Robinia pseudoacacia
Robinia viscosa
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 viscosa can be distinguished from other predominantly pinkish-petaled species by having glands while lacking a hispid indument, often in combination with leaves having more than 13 leaflets.
Robinia viscosa appears to be native in North Carolina, South Carolina, Tennessee, and Virginia (D. Isely 1998), and should be considered introduced in other areas.
D. Isely and F. J. Peabody (1984) and Isely (1998) distinguished two varieties of R. viscosa: var. viscosa with flat, sessile glands on young growth and inflorescences, and glabrous; and var. hartwigii without flat, sessile glands, and densely glandular-pubescent.
Nothospecies based on putative hybrids involving Robinia viscosa and R. hispida (R. × ashei Schallert, R. × longiloba Ashe) are found in North Carolina and South Carolina; those involving R. viscosa and R. pseudoacacia (R. × ambigua Poiret) are found in western North Carolina.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
LA Plants, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
