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International Dendrology Society

Robinia luxurians (Dieck) Schneid.

Modern name

Robinia luxurians (Dieck) Rydb.

Synonyms

R. neomexicana var. luxurians Dieck; R. neomexicana sens. some authors, not A. Gray

A deciduous shrub or small tree 20 to 40 ft high, with a trunk 12 in. or more thick; branchlets downy. Leaves pinnate, 6 to 12 in. long, with downy stalks; leaflets fifteen to twenty-five, oval to slightly ovate, 1 to 13⁄4 in. long, 1⁄2 to 2⁄3 in. wide, with a bristle-like tip; stipules spiny, ultimately 1 in. long. Racemes 2 to 3 in. long, 2 in. wide, the stalk covered with brown shaggy hairs. Flowers 3⁄4 to 1 in. long, pale rose, each on a hairy stalk 1⁄4 in. long; the standard petal large, the calyx glandular, shaggy, with slender teeth. Pods 3 or 4 in. long, 1⁄3 in. wide, covered with gland-tipped bristles 1⁄8 in. or more long. Bot. Mag., t. 7726.

Native of Colorado, New Mexico, Arizona, and S. Utah, in places at 7,000 ft above sea-level. First discovered by Dr Thurber in 1851; introduced to Kew in 1887. It flowers prettily every year in June, and frequently a second time in August. It differs from R. pseudacacia in its bristly pods, and from R. viscosa in the young twigs not being viscid. The larger of two examples at Kew measures 50 × 6 ft (1968).

R. luxurians was at one time confused with R. neomexicana A. Gray, a related species from New Mexico, which makes a shrub to about 6 ft high; its leaves have not more than fifteen leaflets and its pods are hairy but not glandular-bristly.

R. × holdtii Beissn. – A hybrid between R. luxurians and R. pseudacacia whose racemes are looser and longer than in R. luxurians and the flowers of a paler colour. The keel and wing-petals are almost white, the standard pale red with white markings. Habit and vigour of growth similar to those of R. pseudacacia. Pod rather glandular. Obtained by Mr Von Holdt, Alcott, Colorado, and put into commerce about 1902.

The same hybrid was raised in Späth’s nurseries, Berlin, in 1893 from seeds of R. luxurians. This clone, named ‘Britzensis’, is very near to R. pseudacacia in its flowers, but the pods are glandular. The tree named R. coloradensis by Dode was one of six raised by Vilmorin at Les Barres from seeds collected by E. L. Berthoud at Golden, Colorado, probably from a tree of R. × holdtii. Another of the seedlings is described in Fruticetum Vilmorinianum (1904), p. 54, as ‘R. neomexicana var.?’.

From the Supplement (Vol. V)

The specimen at Kew, probably from the original introduction of 1887, measures 70 × 51⁄4 ft (1981). In the University Botanic Garden, Cambridge, pl. 1958, it is 48 × 33⁄4 ft (1982).

R. × holdtii – Mr Bean’s statement that this hybrid grows as vigorously as R. pseudoacacia ought to have been amended. Two specimens in the Kew collection, over eighty years planted, measure only 48 × 33⁄4 ft and 52 × 23⁄4 ft (1981). The cultivar ‘Britzensis’, however, planted at Borde Hill, Sussex, in the 1930s, has reached 62 × 41⁄4 ft (1984).

Genus

Robinia

Other species in the genus

Modern name

Some names used by Bean have now been superseded and are no longer familiar. To ensure that all plants can be easily found, under any name, we have cross-referenced to The Plant List, a collaboration between RBG Kew, Missouri Botanical Gardens and other organisations, which aims to provide a currently accepted name for any plant. Not all taxonomists will agree with all Plant List nomenclature, but it provides a baseline to compare names. For each species above, clicking on the Modern Name will link to the entry for that name on The Plant List website.

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