Flora of the Southeastern United States

Hydrangea Linnaeus. Common name: Hydrangea, Sevenbark.

Key to Hydrangea

A genus of about 45 species, shrubs and lianas, of e. North America and e. Asia. Molecular analyses have long suggested that Hydrangea as usually interpreted in the late 20th century is polyphyletic (Soltis, Xiang, & Hufford 1995; Samain, Wanke, & Goetghebeur 2010; Yang et al. 2023) and should either be circumscribed more broadly to include other genera in tribe Hydrangeeae that are phylogenetically embedded (including, in our area, Decumaria), an approach that has been further developed and formalized by De Smet et al. (2015) and Yang et al. (2024). Alternatively, Hydrangea s.l. could be separated into multiple, monophyletic segregate genera, an approach promoted by Ohba & Akiyama (2016). Yang et al. (2023) show the divergence of Hydrangea s.l. commencing in the late Oligocene (about 24 MYA), and a clade structure not conducive to recognition of traditional segregates. For now, we have followed the broad approach (with generic and sectional circumscriptions following Yang et al. 2024). If split along the lines of Ohba & Akiyama (2016), our species would potentially end up in 4 genera: Hydrangea s.s. (arborescens, cinerea, radiata, and quercifolia), Decumaria barbara, Heteromalla paniculata, and Hortensia macrophylla. See Dirr (2004) and van Gelderen & van Gelderen (2004) for information on cultivated hydrangeas.

References: Boufford & Wood (1977); Freeman (2016b) In Flora of North America Editorial Committee (2016); Hufford (2004) In Kubitzki et al. (2004); McClintock (1957); McGregor (2016b) In Flora of North America Editorial Committee (2016); Ohba & Akiyama (2016); Pilatowski (1982); Samain, Wanke, & Goetghebeur (2010); Yang et al. (2023a); Yang et al. (2024). Show full citations.

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