Cornus × dubia Rehder — Rehder dogwood

Introduction

Rehder dogwood (Cornus × dubia) is the named hybrid between silky dogwood (C. amomum) and cinnamonleaf dogwood (C. quinquenervis). Rehder described it from material that arose spontaneously at the Arnold Arboretum, where the Chinese parent was then known as C. paucinervis. That older parental name is now blocked by an earlier fossil homonym, so Tree TSAR uses the modern formula C. amomum × C. quinquenervis (Rehder 1924; Deasy et al. 2026).

Both parents belong to Subgenus Thelycrania, but they represent geographically distant North American and East Asian lineages. The hybrid is therefore chiefly a cultivated-contact phenomenon rather than a naturally recurring element of either parent’s native flora. Its historical value lies in showing that reproductive compatibility can persist across substantial evolutionary and geographic separation within the subgenus.

Horticultural and Agricultural Uses

Cornus × dubia has never developed into an important commercial ornamental. In collections it is most useful as a documented hybrid, where the identity and provenance of the parental plants can be retained. The broad leaves and intermediate shrubby habit may be attractive, but anonymous plants should not be assigned to the hybrid solely because they look intermediate.

Living accessions are especially informative when accompanied by old labels, herbarium vouchers, or accession records tying them to the original cross. That documentation is more valuable scientifically than propagation of unverified material under the name.

Conservation Concerns

No separate wild conservation assessment is appropriate for Cornus × dubia. The named hybrid originated in cultivation and is not a distinct wild conservation unit. Its conservation value is historical and genetic: authenticated living material preserves evidence of cross-compatibility between two lineages of Subgenus Thelycrania.

Additional Information

Trees and Shrubs Online (opens in a new tab) - Parent-species account noting the spontaneous Arnold Arboretum hybrid.
Plants of the World Online (opens in a new tab) - Kew search for the hybrid name and current nomenclatural treatment.
International Plant Names Index (opens in a new tab) - Nomenclatural search for the published hybrid name.

References and Further Reading

Rehder A (1924) Cornus dubia (C. amomum × paucinervis), hybr. nov. Journal of the Arnold Arboretum 5: 239.

Deasy M, Crowley D, Aldridge J, Chişu R (2026) Cornus quinquenervis. Trees and Shrubs Online. https://www.treesandshrubsonline.org/articles/cornus/cornus-quinquenervis/ (opens in a new tab)

Murrell ZE, Poindexter DB (2016) Cornaceae. In: Flora of North America Editorial Committee (eds) Flora of North America North of Mexico, vol. 12. Oxford University Press, New York and Oxford. https://www.efloras.org/flora_page.aspx?flora_id=1 (opens in a new tab)

Du Z-Y, Xiang Q-Y, Cheng J, Zhou W, Wang Q-F, Soltis DE, Soltis PS (2023) An updated phylogeny, biogeography, and PhyloCode-based classification of Cornaceae based on three sets of genomic data. American Journal of Botany 110(2): e16116. https://doi.org/10.1002/ajb2.16116 (opens in a new tab)