Poncirus trifoliata, known on its common name as Japanese bitter orange, is a close relative of the orange tree and can withstand northern European winters, as it can survive at -20 Celsius degrees (-4 F) even its origins are in woodlands of China and Korea.
Poncirus is a deciduous shrub that produce alternate 3-palmate, dark green leaves. This shrub is very attractive in winter, with its bare green branches filled with flower buds like impressive green thorns.
It flowers in May wearing 5-petaled flagrant white flowers, at the same time as the new light-green foliage appear. Later in summer the foliage will turn dark-green and the orange-like fruits will appear. The fruits are first green, then orange, extremely sour, inedible but very flagrant.
Poncirus likes a well drained, fertile soil and a place in a sunny position, with shelter from cold, dry winds. You can grow it in a border or against a sunny wall or as a very thick, thorny hedge.
Poncirus is often used as a rootstock for Citrus cultivars because of its vigorous growth and hardiness.
You can propagate this shrub by sowing seeds in containers in a cold frame in autumn or by taking semi-ripe cuttings with bottom heat in summer.
