Credit: David Foley
Idesia polycarpa
Background and story
Idesia polycarpa is the sole species in its genus, native to China, Japan, Korea, and Taiwan, where it grows in moist forest sites, often at moderate to high elevations.
It was first collected in Japan in 1860–61 by the Russian botanist Karl Maximovich, who later formally described the species in 1866, establishing the genus Idesia.
Seeds were also sent to Kew shortly afterwards by the plant collector Richard Oldham, helping introduce it into British and Irish cultivation during the later 19th century.
Despite this early introduction, it has remained relatively uncommon, more often encountered in arboreta and specialist collections than in everyday gardens.
Did you know?
The name polycarpa means “many-fruited”, which is very fitting for a female Idesia polycarpa tree covered in its long chains of bright red berries.
Hardiness and conservation
The recorded RHS hardiness rating is H5, which means this plant is hardy in most places, including many severe winters, provided other site conditions are suitable. The recorded USDA/PFAF hardiness value is 6, which is useful as a broad winter-temperature guide, but it should not be read as a direct substitute for the RHS rating. Local hardiness always depends on local shelter, drainage, winter wet, salt-laden wind and the plant’s age and establishment.
The IUCN Red List status recorded here is Not Assessed (NA).
Additional notes for Ireland and Britain
In Ireland and the UK, Idesia polycarpa is fully hardy (RHS H5–H6), tolerating winter temperatures to around −15°C or lower once established, though young shoots can be damaged by late spring frosts. It forms a medium to large tree (8–12 metres or more) with an open, tiered structure and large, almost tropical foliage. It grows best in deep, fertile, moist but well‑drained soils in sun or light shade, and benefits from shelter when young. The species is dioecious, meaning male and female plants are separate; only female trees bear the long, pendant clusters of red berries, and these require a nearby male for reliable fruiting. In mild Irish conditions, especially in sheltered woodland or large garden settings, it can be both vigorous and highly ornamental, with fragrant summer flowers followed by striking autumn and winter fruit displays.
Globally, Idesia polycarpa is considered not threatened, with a wide natural distribution across East Asia and stable populations in the wild. It is not currently listed as endangered, and its adaptability across a range of forest habitats has contributed to its resilience. In cultivation, it is also secure, with a long history in botanical collections and increasing interest as an ornamental tree. While not common, it is well established and not at conservation risk, either in the wild or in horticulture.
Notable features
- It is the only species in its entire genus. Idesia polycarpa is monotypic, meaning it is the sole species in the genus Idesia, which is unusual among ornamental trees.
- Male and female trees are separate (and both are needed for berries). The species is dioecious, so one tree produces male flowers and another female flowers; only females bear fruit, and usually only if a male is nearby.
- Its berries hang like bunches of grapes. The fruits are carried in long, pendulous clusters that resemble strings or bunches of small grapes, a distinctive and highly ornamental feature.
- It provides wildlife food in winter when little else is available. The bright red berries often persist well into winter, providing a valuable food source for birds during a lean period.
- Its seeds are rich in oil and have economic potential. The fruits contain seeds that are oil-rich, and the species has been studied as a potential source of edible or industrial plant oils.