Plant of the Month: May

Kerria japonica Common name: Japanese rose Family: Rosaceae Vital statistics Height and spread: 2m (6ft) x 2.5m (8ft) Form: Deciduous shrub Soil: Fertile and well drained. Aspect: Full sun or partial shade. Hardiness: Fully hardy.

Kerria japonica @ Harlow Carr

We have twoKerria japonica at Harlow Carr. The first is within the main herbaceous borders. Turn right at the bottom of the steps at the entrance to the gardens, continue along the path, turning left into the main borders just after the entrance to the plant centre. Kerria japonica 'Pleniflora' is in the third border on the right hand side.The second is in the Winter Garden. Turn right at the bottom of the steps at the entrance to the gardens, continue along the path, turning left at the Herb Garden. Follow the path down past the fuchsia beds to the first main bed on the right hand side.

Kerria

Kerria is a genus of one species of deciduous, suckering shrub from the woodlands of China and Japan. Its leaves are alternate, simple and bright green and its flowers are solitary, yellow and saucer- or cup-shaped.

Kerrias are grown for their foliage and flowers and are suitable either for a shrub border or for an open part of a woodland garden.

This genus was named for William Kerr, a gardener and plant collector at Kew, who collected in China, Java and the Philippines.

Kerria japonica

K. japonica is a suckering shrub with graceful, arching, cane-like stems that is found in the mountains of Japan and south western China.

The leaves are up to 10cm (4in) long, bright green, simple and alternate with prominent veins, downy beneath and turn yellow in autumn.

In mid to late spring, solitary, single or double, bright golden flowers are produced, 3 - 5cm (1.25 - 2in) across.

'Pleniflora' AGM syn. 'Flore Plena' is a vigorous, upright form with double flowers 3cm (1.25in) across. It grows to 3m (10ft) in height.

'Picta' (syn. 'Variegata') is a low, spreading cultivar up to 1.5m (5ft) in height, with creamy white margins on grey-green leaves.

'Golden Guinea' AGM has very large, single flowers up to 6cm (2.5in) across and bright green, attractively veined leaves.

AGM

The RHS Floral B Committees awarded K. japonica 'Golden Guinea' an Award of Garden Merit and described it as: Suckering medium-sized deciduous shrub with bright green, lanceolate, attractively veined leaves. Large, single bright yellow flowers are borne along the arching green shoots

The RHS Floral B Committees awarded K. japonica 'Pleniflora' an Award of Garden Merit and described it as: Suckering medium-sized deciduous shrub. Leaves narrowly ovate, strongly veined. Flowers double, bright deep yellow.

Cultivation

Grow in fertile, well-drained soil, in full sun or partial shade.

Prune by removing several older flowering shoots at the base of the plant each year after flowering, in order to make room for new shoots.

K. japonica is generally free from pests and diseases.

Propagation

Take greenwood cuttings in summer or layer stems and lift a year later.

Divide in autumn.