Spreading shrub to c. 3 m tall. Twigs rounded, with appressed hairs into their second year; pith chambered. Leaves ovate, c. 8 cm long, with a pointed tip and a rounded base; margin serrate or entire; with some appressed hairs underneath, near the base of the main veins; petiole with appressed hairs. Flowers in spring, solitary; corolla bright yellow, with ovate to oblong lobes only 11–13 mm long. (Nakai 1930).
Distribution North Korea Mt Chojusan
Habitat Mountain forests.
USDA Hardiness Zone 4
RHS Hardiness Rating H7
Conservation status Not evaluated (NE)
Taxonomic note Forsythia nakaii was first described by Takenoshin Nakai in 1930 under the name F. densiflora, but this name had already been used by Bernhard Koehne in 1906 for the garden forsythia now known as F. × intermedia ‘Densiflora’; in 1942 Nakai renamed his species as F. velutina. This name is still widely used, but a plant with identical features from the same habitat had been described two years earlier by Homiki Uyeki as Rangium nakaii. Leaving aside the question of whether two visually indistinguishable taxa co-exist in this area, José Ignatio De Juana Clavero showed in 2016 that the correct name for this plant should be Forsythia nakaii (Uyeki) T. Lee, a combination first published in 1966 (De Juana Clavero 2016).
Forsythia nakaii is readily distinguished by its persistently downy shoots. Like the other species endemic to Korea, it has only been recorded as a tiny relic population, but as this lies just to the north of the present Korean border, no information is available about the plant’s current survival in the wild (De Juana Clavero 2016). It is however cultivated in Hongnung Arboretum in Seoul, from where it was introduced to the Sir Harold Hillier Gardens in Hampshire in 1981 (Royal Botanic Garden Edinburgh 1997). Genetic analysis has suggested that F. nakaii is most closely related to F. japonica (Ha et al. 2018).
‘Nakai’ (or ‘Nakkia’) is occasionally encountered as the name of a forsythia cultivated in the west, but it would appear to refer to F. ovata and to have arisen through confusion with the botanical authority for that species, which was also named by Nakai.