General description
Kerria japonica 'Pleniflora' (Double kerria) is a bushy fully hardy perennial deciduous shrub with yellow flowers in early Spring and mid Spring. It grows well in shade and semi-shade, and prefers medium levels of water. The flowers are explosion shaped. It has high drought tolerance. It looks best in Spring.
This is a arching shrub has an ultimate height of 3m / 9.8ft and spread of 3m / 9.8ft. It can take 6-10 years to reach its ultimate height.
Plant requirements
Kerria japonica 'Pleniflora' grows in soils ranging from a pH of 4.5 (extremely acidic ranges from 0 to 5.1) to 8.5 (alkaline ranges from 8.1 to 8.5). It is adapted to chalk, clay, loam, peat and sand soils, and prefers low fertility.
Maintenance
Early-flowering shrubs are pruned after flowering (in late winter to spring and early summer, depending on the shrub).
They usually flower on the previous year’s growth. Pruning immediately after flowering allows the maximum time for development of young growth to provide the following year’s flowers before the end of summer.
Pruning requirements depend on the type of shrub, but all early-flowering shrubs need routine removal of damaged, diseased or dead wood, as follows:
Cut out any damaged or dead shoots back to their point of origin or to ground level
Where there are many stems remove some to ground level to keep the bush open and avoid congestion
Finally take out any weak, spindly or twiggy shoots right to the point of origin or to ground level so the plant concentrates its resources on strong new shoots that will bear the best flowers
Deciduous shrubs producing new flowering growth from or near ground level (Pruning group 3)
Timing: Prune immediately after flowering
Examples: Kerria, Neillia
Pruning: Remove flowered shoots back to vigorous sideshoots. Cut back one in three stems to ground level each year.
After pruning, mulch and feed.
Practical use
City courtyard garden, cottage informal garden, drought resistant, flowering shrub, shade plant, small garden/space and wall side.