Pieris japonica 'LITTLE HEATH GREEN' lily-of-the-valley shrub

Pieris

The genus Pieris belongs to the heath family and comprises roughly seven species distributed across eastern Asia and North America, regions characterised by misty valleys, acidic soils and forests with a deep layer of humus. Fossil evidence is scarce but confirms that the genus is old and stable, without dramatic evolutionary shifts, which corresponds well with its present appearance and ecological requirements. It was described botanically by David Don (1799–1841) in the first third of the nineteenth century, at a time when European botany began to study woody plants from eastern Asia in a systematic way. It is worth noting that Pieris does not appear in the landmark work Species Plantarum of 1753, which described much of the botanical world at the time, because Linnaeus did not know the genus and it entered European science only several decades later. For a long time Pieris was the subject of minor disputes over its precise delimitation; some older works placed it close to Lyonia or Andromeda because of its similar bell-shaped flowers and leathery leaves. Its distinctiveness was eventually recognised, especially thanks to its characteristic alternation of growth phases, its toxic glycosides and its marked ability to thrive in acidic, nutrient-poor soils. In horticultural history the genus became well known mainly thanks to the Japanese and Taiwanese species, which became popular ornamental shrubs in European parks by the late nineteenth century.

Pieris japonica, lily-of-the-valley shrub, originates from the mountainous regions of Honshu, Shikoku and Kyushu, where it grows in lightly shaded forests together with rhododendrons and cryptomerias, so its natural environment can easily be imagined as calm, moist slopes with soft light. The species was described by Carl Peter Thunberg (1743–1828), who during his stay in Japan in the 1770s collected extensive botanical material and filled gaps that Linnaeus could not address. Within the species a group known as yakushimanum gradually became distinguished, named after the island of Yakushima, where compact, low-growing forms occur with dense branching, smaller leaves and exceptional resistance to wind and humid weather; they often grow on exposed, sunny slopes. These plants later formed the basis of modern cultivars with a firm habit and pronounced spring flush. Pieris japonica differs from other species by its more marked spring onset of new shoots, which appear gradually in several distinct stages, by its abundant flowering and by its ability to form sturdy evergreen shrubs even in deeply acidic soils that may be humus-rich or nutrient-poor, reflecting the varied conditions of its Japanese homeland.

In Japanese garden culture Pieris japonica is a symbol of calm and constancy, because its evergreen leaves and early spring flowering act as a gentle counterbalance to rapidly changing seasons. It reached Europe in the 1830s and 1840s and is documented in British gardens by around 1850, fitting naturally into the then fashionable Japanese corners of urban parks. It arrived in North America later, only at the end of the nineteenth century, because nurseries there preferred the native Pieris floribunda, which was reliable and well known to growers. Only in the twentieth century did the Japanese pieris become a valued ornamental shrub in the United States, appearing in modern breeding programmes that made use of its finer habit and abundant flowering. In our gardens it is most noticeable in spring, flowering at a time when most shrubs are only beginning to gain strength, and again with the arrival of warmer weather when it produces new coloured leaves.