Cornus amomum Mill.

Cornus amomum is native to eastern North America, where it is one of several similar-looking blue-fruited dogwoods found in moist environments (others are C. foemina, C. obliqua and C. racemosa). The name C. sericea was misapplied to the species at an early date (see below), a case of mistaken identity that proved persistent and which complicates the attempt to trace its early history in cultivation. The distinctive characters of C. amomum are the purple young stems with brown pith, silky reddish down beneath the leaf, and above all the remarkable blue fruits that gained it early notice among seventeenth-century European colonists. In the best forms, these are a vivid caerulean, more brilliant than those of the other related species, though they share the tendency to fade in bright sunlight.

Plukenet illustrated the species in his Phytographia (1692, tab. 169; also 1696), remarking on the ‘blue berries of a most elegant colour’ and noting that the plant ‘was called by some the Amomum of New England.’ In classical culture, amomum was the name for an exotic aromatic shrub that yielded a prized balsam, mentioned by Ovid (Metamorphoses, Book 15) as one of the foods of the legendary phoenix. Plukenet’s allusion probably alludes to the fragrant inner bark, prized by many native American tribes when dried for smoking in ritual ceremonies (‘Kinnikinnik’). Among the Ojibwe and Menominee of Wisconsin, the flavours of different species of dogwood were said to be quite distinct, with Cornus sericea (gēga’daganagēgok) favoured above all, followed by C. amomum (wo’banūyak) and then C. racemosa (mūʒû’mic). The young stems were harvested and the outer bark carefully removed before the inner bark was pared in narrow ribbons that were dried over a fire and stored for use (Barrett 1911). An infusion of the bark of C. amomum was used by the Iroquois as a wash to make babies sleep (Herrick 1995).

The suspiciously early year of introduction of 1683 given by Don (1834), repeated by many that followed (including Bean 1976), cannot be substantiated. Aiton (1789) proffers a more plausible date of 1759, together with the information that Philip Miller introduced the species, presumably at the Physic Garden in Chelsea. Actually, Cornus amomum is recorded (using Plukenet’s 1696 polynomial) as early as the first edition of Miller’s Gardener’s Dictionary (1735), which describes it as ‘at present pretty rare in England’. By the seventh edition (Miller 1759), we learn that the shrubby American dogwoods, including C. amomum, ‘all thrived well in the in the open Air in England; so are cultivated by the Nursery Men near London, to add to the Variety of their hardy Trees’. As both Cornus minor and C. ferruginea, the ‘blue-fruited dogwood’ appears to have been cultivated at the Jardin du Roi, Paris by the mid 1780s (Lamarck 1786).

The confusion with Cornus sericea originates with L’Héritier (1788), who described the blue-fruited species under that name, citing C. amomum in synonymy. Pursh (1819), Don (1834) and Loudon (1838) all followed suit, perhaps also misled by Miller’s 1759 allusion to red stems and white leaves, text intended – as shown by Rickett (1934) – to apply not to C. amomum, but to another shrubby American dogwood under discussion.

Cornus amomum has sometimes been treated as including the closely related C. obliqua, the latter species now generally recognised as distinct on the basis of its leaves, which are narrower and paler beneath, and by differences in leaf pubescence, though intermediate forms are widespread where the ranges overlap (Murrell & Poindexter 2015). The Flora of North America indicates that in C. amomum the secondary veins tend to originate in the proximal half of the leaf, being more evenly spaced in C. obliqua (Murrell & Poindexter 2015), though observation suggests that this character might not be found in cultivated plants. The vernacular name ‘silky dogwood’ is a curious result of the historical misapplication of the name C. sericea (Latin sericea = silk-like), which applies far better to the type of C. sericea than it does to this species (Fosberg 1942).

Like the other shrubby members of subgenus Thelycrania, the species’ horticultural value has generally been viewed as minimal, the consensus being that it is best deployed in utilitarian roles such as natural reclamation projects or bank stabilisation (Cappiello & Shadow 2005; Dirr 2009). This rather grudging assessment is, however, belied by the introduction of a number of cultivars, suggesting that the species may have more to offer in terms of horticultural interest: the purple stems in winter, and the vivid fruits are indeed striking. To be seen to their best advantage plants do require ample space (a radius of at least 3 m) to spread, proving particularly valuable in waterside plantings, there being ‘no better shrub to plant by the margins of ponds and streams where its long branches can hang gracefully over the water’ (Arnold Arboretum 1923).

Cornus amomum thrives in moist conditions, in full sun or partial shade, but Dirr 2009 notes that it is very tolerant of the droughty heat of the deep South (Georgia). Germination of the seed requires longer cold stratification than other Cornus species (up to 180 days); softwood and hardwood cuttings root well if treated with IBA (Cappiello & Shadow 2005).