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Robinia hispida var. kelseyi (Cowell ex Hutch.) Isely

Kelsey locust

Synonyms
  • Robinia kelseyi Cowell ex Hutch.
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Introduction

Kelsey locust is the most taxonomically problematic entity that Tree TSAR presently retains within Robinia hispida. It is a deciduous woody shrub or small tree with comparatively slender, nearly glabrous branches, usually nine or eleven relatively narrow, pointed leaflets, bright rose-colored flowers, and conspicuously glandular flower stalks and fruits. Unlike the triploid typical and rosea varieties of R. hispida, var. kelseyi is diploid. (Whitaker 1934; Isely & Peabody 1984)

Its biological origin, however, remains unresolved. The plant entered horticulture around the beginning of the twentieth century through nurseryman Harlan P. Kelsey, and no ancestral wild population has been securely tied to the cultivated lineage. Isely and Peabody were unable to establish a convincing natural source, while later regional records under the name kelseyi have not yet demonstrated that they represent the progenitor of the horticultural taxon. GRIN accordingly treats its natural origin as uncertain and documents the taxon principally from cultivation.

Modern genomic evidence has made the problem more interesting rather than resolving it. Wheeler’s RAD-seq study detected an exceptionally strong signal of shared genetic material between the sampled var. kelseyi and R. pseudoacacia. His analyses suggested introgression or even hybrid origin involving black locust and a member of the R. hispida complex. Sampling of kelseyi was extremely limited, however, so this result cannot yet support formally treating the variety as a nothotaxon. (Wheeler 2023)

Tree TSAR therefore retains R. hispida var. kelseyi provisionally. The page represents an identifiable biological and horticultural entity, but its status as a naturally evolved variety remains unconfirmed. Plants of the World Online currently sinks the name into R. hispida.

Horticultural and Agricultural Uses

Kelsey locust owes much of its botanical history to horticulture. It was distributed commercially by about 1901 and reached Kew shortly afterward. Its vivid pink flowers, relatively smooth shoots, and lighter-textured foliage distinguished it from the more heavily bristled forms of R. hispida, and it became valued as an ornamental shrub or small tree. (Trees and Shrubs Online 2026)

Traditional propagation often involved grafting onto R. pseudoacacia. This produces saleable plants quickly but can be troublesome because the black-locust rootstock may sucker strongly and can eventually dominate a declining scion. Own-root plants can instead be propagated from suckers or root cuttings and avoid that rootstock problem. Trees and Shrubs Online also notes that the branches can be brittle, an important consideration where plants are trained upward as small trees rather than allowed to remain shrubby.

The possibility that Kelsey locust is itself hybrid-derived adds another reason to propagate documented clones carefully. Plants carrying the name may not all represent the same genetic entity, particularly after more than a century of cultivation, movement, and possible crossing with other locusts.

Conservation Concerns

Conservation status is unusually difficult to interpret because the natural lineage itself has not been demonstrated securely. North Carolina’s 2021 rare-plant list nevertheless treated var. kelseyi as S1 and G4T1 and associated reported occurrences with high-elevation red-oak forests and dry rocky woods in the mountains. These records deserve continued investigation, but occurrence under a taxonomic name does not by itself demonstrate that contemporary plants represent the wild progenitor of the cultivated Kelsey locust. (North Carolina Natural Heritage Program 2021)

The highest conservation priority is therefore clarification. Genome-scale sampling should include multiple plants from every credible wild occurrence, old cultivated accessions of documented provenance, var. fertilis, and R. pseudoacacia. Such work could distinguish among several possibilities: a genuine but extremely localized Appalachian lineage, an old hybrid-derived cultigen, or a more complicated mixture of wild and cultivated material. Until that question is answered, conserving well-documented extant material remains worthwhile without implying that its natural history is already understood.

Additional Information

References and Further Reading

Isely D (1982) New Combinations and One New Variety Among the Genera Indigofera, Robinia, and Tephrosia (Leguminosae). Brittonia 34(3): 339-341. https://doi.org/10.2307/2806706

Isely D, Peabody FJ (1984) Robinia (Leguminosae: Papilionoideae). Castanea 49(4): 187-202.

North Carolina Natural Heritage Program (2021) Natural Heritage Program List of Rare Plant Species of North Carolina 2021. North Carolina Department of Natural and Cultural Resources.

Peabody FJ (1984) Revision of the Genus Robinia (Leguminosae: Papilionoideae). PhD dissertation, Iowa State University. https://doi.org/10.31274/rtd-180813-5895

Royal Botanic Gardens, Kew (2026) Robinia hispida var. kelseyi (Cowell ex Hutch.) Isely. Plants of the World Online.

Trees and Shrubs Online (2026) Robinia hispida. International Dendrology Society.

USDA Agricultural Research Service (2026) Robinia hispida var. kelseyi. GRIN-Taxonomy.

Wheeler BT (2023) Molecular and Morphological Tests of Species Delimitation in Robinia of the Southern Appalachians. MS thesis, Western Carolina University.

Whitaker TW (1934) A Karyo-Systematic Study of Robinia. Journal of the Arnold Arboretum 15(4): 353-357. https://doi.org/10.5962/p.185318