Bachelor's Button, Japanese rose, Jew's Mallow, Japanese Kerria

Kerria japonica

Physical Characteristics

Kerria japonica is a deciduous Shrub growing to 2 m (6ft) by 2 m (6ft) at a medium rate. See above for USDA hardiness. It is hardy to UK zone 4. It is in flower from April to May. The species is monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and is pollinated by Insects. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in heavy clay and nutritionally poor soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.

Distribution

E. Asia - China, Japan. A rare garden escape in Britain.

Habitats

Woodland Garden Dappled Shade; Shady Edge;

Edible Uses

Edible Parts: Fruit Leaves Edible Uses: Young leaves - cooked[105, 177]. The leaves contain a small amount (0.002%) of hydrogen cyanide and are also a rich source of vitamin C (200mg per 100g)[218]. Some caution is advised, see the notes above on toxicity. Fruit[177]. No more details are given, but this report is somewhat suspect, the plant does not produce a fleshy fruit and the seed case certainly does not look edible[K]. The fruit is a dry, somewhat plump achene about 5mm in diameter[200].

Medicinal Uses

Vitamin C Women's complaints A decoction of the flowering shoots is used in the treatment of coughs and women's complaints[178, 218].

Known Hazards

The leaves contain small quantities of hydrogen cyanide (prussic acid). In small quantities, hydrogen cyanide has been shown to stimulate respiration and improve digestion, it is also claimed to be of benefit in the treatment of cancer. In excess, however, it can cause respiratory failure and even death.