Kerria japonica 'Shannon'

William Kerr arrived in Guangzhou in 1803 as the first professional plant hunter posted permanently in China, dispatched by Sir Joseph Banks and the Royal Botanic Gardens at Kew to send back whatever the port cities of the south could offer. He did good work for several years. Among his returns was a double-flowered shrub with bright yellow, pompon-like blooms, collected from cultivation and shipped to Kew in 1805. The genus was eventually named for him. His later years were less distinguished — by most accounts he acquired an opium habit, his correspondence to Kew grew sparse, and he died in Ceylon in 1814. The double-flowered form he introduced, 'Pleniflora', went on to become one of the most common shrubs in Victorian gardens, present in nearly every collection of the era and still widely planted today.

The single-flowered species did not reach Western gardens until 1834, nearly thirty years later. It is, in botanical terms, the original: the form that grows wild on mountain slopes in China and Japan, the one that appears in the Man'yoshu, the oldest extant collection of Japanese poetry, where yamabuki — the Japanese name for this plant — carries associations of spring, impermanence, and the particular yellow of mountain streams in early morning light. The double-flowered form is the cultivated elaboration. 'Shannon' is closer to the source.

What 'Shannon' offers over the standard single species is scale. The flowers are large — considerably larger than the typical single form, clear golden yellow, each with the full five-petaled simplicity of a wild rose relative, which is precisely what it is. They appear in spring in generous numbers along the arching green canes, and then continue sporadically through summer in a way the double forms do not manage. The bright green stems persist through winter, remaining vivid and photosynthetically active long after the leaves have dropped — a feature that makes the shrub genuinely interesting in the garden from December through March, which is more than most spring-flowering shrubs can claim.

Kerria japonica thrives in shade that defeats most flowering shrubs, which is the practical argument for growing it. The cultural argument is simply that the single-flowered form is more beautiful than the double, and 'Shannon' is the best version of it available.