Kerria is a type of deciduous shrub from the family Rosaceae. Named after the botanist William Kerr, these are popular ornamental plants that are native to Japan, Korea and China. In Japan, where they are known as Yamabuki, these garden plants have been immortalized in many traditional paintings and poems. The plant is also known as the Yellow Japan Rose on account of its distinctive yellow blooms. The Kerria genus includes only one species, the single flowered Kerria japonica, but cultivars like the double flowered Pleniflora, the single flowered Honshu and Golden Guinea, and the white flowered Alba are also available.
These shrubs can grow up to eight feet (2.4 m) tall normally, and have bright green stems with arching, zigzagging branches. The simple leaves are 1.6 to 2.8 inches (4 to 7 cm)long, are alternately placed, and are lance-shaped with serrated edges. They drop off in the fall and the stems and branches turn a bright yellow in the winter. Even after the leaves have been all cast off, the shrub maintains a striking, attractive appearance. It may be used singly as a stand-alone landscape plant, or many of these shrubs may be planted close together to form a hedge.
The Kerria shrub generally produces flowers throughout the year, and the flowers, whether they are of the single or the double variety, can last for several weeks. The single flowered variety have five petals and look like wild roses, but the double flowered cultivars often resemble chrysanthemums. The flowers eventually produce small, brown and single seeded fruit; unlike the flowers, the Kerria fruits are quite inconspicuous. New plants can be propagated by seed or by new suckers that the plant sends out.
These garden plants should preferably be planted in areas of partial or full shade, as they seem to flower more profusely in shady areas. It is also possible to grow these plants in areas of full sun, but too much sun may wither or bleach the flowers, shorten their life span, and cause the stem to shrivel up.
On the whole, the Kerria plant is hardy and quite easy to maintain. It does not require much fertilization and will do well enough if left to its own devices. It may require some pruning from time to time to get rid of dead branches and to promote better growth; some gardeners like to cut the plant right down to the ground. Pruning should preferably be done after the plant has finished flowering in the spring.