Robinia x margaretta 'Pink Cascade' CASQUE ROUGE black locust

Robinia

Locusts (Robinia) belong to the legume family and form a small genus of deciduous trees and shrubs native exclusively to North America. In their natural habitats they grow mainly on dry, rocky slopes, in open woodland and on disturbed sites, where their rapid growth and symbiosis with nitrogen‑fixing root nodules give them a clear advantage. They were introduced to Europe at the beginning of the 17th century and quickly gained popularity not only as ornamental trees, but also as valuable timber and reclamation species. Typical features of the genus include pinnate leaves, thorny branches and papilionaceous flowers arranged in pendulous racemes that appear in late spring. Black locusts are valued for their tolerance of drought, pollution and poor soils, while their light, airy crowns allow plenty of light to pass through, giving them a distinctive, open character.

Casque Rouge is among the most striking ornamental locust trees grown in gardens of the temperate zone, immediately recognisable by the colour and size of its flowers. It is not a botanical species, however, but a garden hybrid with a surprisingly complex background. It originated from a cross between Robinia pseudoacacia and Robinia hispida var. kelsey. From the former it inherited the length and structure of the flower racemes, from the latter their intense colouring. The exact circumstances of its origin remain a matter of debate, which only adds to its appeal. Specialists at Kew Gardens believe it was originally a spontaneous hybrid discovered as early as 1914 in Durand–Eastman Park in Rochester, New York (USA). It was found by B. H. Slavin and described under the name Robinia × slavinii. Another record dates from 1933, when British growers at the Hillier nursery achieved the same result through deliberate crossing and introduced it under the cultivar name ‘Hillieri’. Just a year later, the American nursery Princeton Nurseries in New Jersey presented the identical tree as Robinia × ambigua ‘Pink Cascade’. And finally comes the greatest mystery of all – for reasons that remain unclear, the same tree appeared much later in Europe under the French name ‘Casque Rouge’. With such an identity crisis, one might almost feel sorry for it.