Cornus disciflora DC.

Cornus disciflora is a rare beast – a tree from the tropical and subtropical cloud forest that bears cultivation in the open in Northern Europe. Found in mountain environments throughout central America, the species belongs in subgenus Cynoxylon, allied to the North American large-bracted dogwoods C. florida and C. nuttallii. Like them, it bears small heads of flowers at the shoot tips, but differs in that the enclosing bracts fall before the flowers open, without expanding into the highly ornamental white ‘petaloid’ involucres for which the northern species are celebrated. The distinctive tight globular clusters of whitish flowers are no more than understated, but the fruits, which resemble clusters of acorns when green, ripen to a dark bluish-purple that complements the handsome foliage. The pale undersides of the leave are striking, reflected in the Tzeltal name for the plant, Sak Hi, ‘hi’ meaning white (Berlin, Breedlove & Raven 1974).

In the wild state, Cornus disciflora grows as an understorey species in association with Quercus, Pinus, Liquidambar and Nyssa, Oreopanax and Clethra. Its IUCN conservation status was formerly assessed as Vulnerable, owing to timber exploitation and habitat decline (Oldfield, Lusty & MacKinven 1998), but has since been raised to Least Concern thanks to effective conservation measures (Zamora 2021).

In the United States, cultivated specimens are sometimes labelled Cornus floccosa (e.g. Huntington Garden, Acc: 73395), a name placed in synonymy with C. disciflora by most modern authorities but formerly used to describe plants with spreading rather than appressed hairs, sometimes treated as the form C. disciflora f. floccosa (Wang.) Rickett. In practice, such distinctions have been found to be of questionable significance, with different pubescence states sometimes found on the same plant. Taxonomically speaking, the two names do not appear to have any geographical or ecotypical significance, though the remarkable claim that North American plants labelled C. floccosa have retained their leaves in temperatures as low as –18C° (Hogan 2008) is a reminder that the provenance of material material intended for cultivation in marginal climates is worth close attention, particularly with respect to altitude.

The presumed purpose of the ostentatious involucral bracts in related species is to attract the insect pollinators necessary to facilitate reproduction. Despite losing those organs, however, Cornus disciflora does not exhibit any other obvious strategies for attracting pollinators (the flowers are not reported to be scented). From an evolutionary (adaptationist) perspective, this raises some awkward questions, since the genus as a whole is generally held to be self-infertile. Eyde (1988) noted that the most obvious implication of the species’ having dispensed with its showy involucre was that it must be self-pollinating, though this remains to be demonstrated experimentally, since pollination syndromes do not always match what might be predicted in theory, and Eyde himself (reporting the observations of Breedlove) noted that nectar-feeding flies may be observed on the inflorescences.

In its native range the tree is used as a source of firewood, and (like its distant transatlantic cousin Cornus mas ) for hoe handles, as well as for timber for house construction, particularly roof purlins and rafters (Berlin, Breedlove & Raven 1974).