The Double Flowered Japanese Kerria, Kerria japonica ‘Pleniflora’, is a deciduous shrub known for its vibrant early spring display. It features golden, pom-pom-like blooms that appear before much of the garden awakens. Its distinctive bright green stems also provide visual interest throughout the colder months.
Defining Characteristics
Double Flowered Japanese Kerria showcases distinctive double, spherical yellow flowers, typically measuring about 2 inches across, resembling small pom-poms. These blooms provide an extended flowering period in spring, often appearing from late March to mid-April, and can sporadically re-bloom later in the season. During winter, its bright green, cane-like stems maintain their color, adding visual appeal to the dormant landscape. The plant typically grows with an open, rounded habit, reaching heights of 3 to 10 feet and spreading 6 to 10 feet wide, often forming natural thickets through suckering growth.
Planting and Growing Conditions
Establishing Double Flowered Japanese Kerria begins with careful site selection. It performs well in full sun to partial shade, though intense sunlight can fade its golden flowers. For optimal blooming, a spot with morning sun and afternoon shade is often ideal. The plant adapts to various soil types but thrives in well-drained, loamy soils, tolerating a wide pH range. Avoid heavy clay soils; amending with compost improves drainage.
Initial watering is important for establishment, requiring deep and regular moisture during its first growing season. Once established, it tolerates occasional dry spells but prefers consistently moist conditions. Double Flowered Japanese Kerria is hardy in USDA zones 4 through 9 and tolerates urban pollution.
Pruning and Maintenance
Proper pruning encourages abundant blooms and maintains the desired shape. The optimal time to prune is immediately after flowering in spring, typically from late March to mid-April. This timing is important because the plant blooms on old wood, with next year’s flowers forming on current season’s stems. Renewal pruning, a common practice, involves removing about one-third of the oldest, less productive canes from the plant’s base.
This method helps rejuvenate the shrub, promotes new growth, and improves air circulation. Remove dead or weak stems as they are noticed. Fertilization needs are minimal; a light application of a slow-release fertilizer in early spring is sufficient. While generally robust, observe the plant for any signs of pest or disease issues.
Propagation
Double Flowered Japanese Kerria can be propagated through softwood cuttings and division. Softwood cuttings are best taken from May to July from healthy, non-flowering shoots. Cuttings, typically 4 to 6 inches with several leaf nodes, should have lower leaves removed. Dipping the cut end in rooting hormone can significantly increase the success rate. Plant these cuttings in a well-draining medium, maintain consistent moisture, and place them in dappled light to encourage root development.
Division is another method, utilizing the plant’s natural suckering habit. Dig up and separate suckers that emerge from around the base of the established shrub. Replant these rooted sections in a new location, keeping them well-watered for establishment.
Common Challenges
Gardeners may encounter challenges when growing Double Flowered Japanese Kerria. A primary concern is a lack of blooms, often from incorrect pruning timing; pruning too late removes flower buds formed on previous year’s growth. Insufficient light, whether too much shade or intense sun, also impacts bloom quantity. Leggy growth is another issue, as the shrub’s suckering habit can lead to dense, unruly thickets if not managed.
Addressing these issues involves adjusting light exposure and implementing proper renewal pruning to encourage bushier growth and abundant flowering. While generally resistant to pests and diseases, Kerria can occasionally be susceptible to leaf spots and blights, such as Kerria twig and leaf blight caused by the fungus Blumeriella kerriae. This may manifest as red-brown spots with purple borders on foliage. Ensuring good air circulation and removing diseased parts can help mitigate such problems.