Japanese rose (Kerria japonica) is a deciduous flowering shrub with birch-like leaves and five-petaled yellow flowers that resemble those on old-fashioned roses. It blooms in spring and sometimes again later in the summer. Although it belongs to the Rosaceae family, it is in a different genus than common garden roses. Japanese rose is among the rare flowering shrubs that blooms fairly well in part shade.
In addition to attractive yellow flowers, the bark and branches are also of interest. The main branches on the double flowering type arch gracefully to a height of 8 to 10 feet (the width can be restricted to similar dimensions through general pruning and, specifically, the removal of suckers). Smaller branches radiate off the main ones in all directions. The branching pattern thus affords interest both vertically and horizontally; it is also relatively airy. The bark is a pleasing Kelly green to greenish-yellow—a color retained throughout the winter.
Japanese rose does not make a good formal hedge because it would require extensive pruning, but it can work suitably as an informal screen. It also works very well for shady woodland gardens and shrub borders, where it can be allowed to sucker and spread.
Japanese rose is generally planted as a nursery-grown potted specimen in spring or fall. It grows relatively fast, achieving its full size in the first year after planting a container-grown specimen.
|Botanical Name||Kerria japonica|
|Common Names||Japanese rose, Kerria rose, Easter rose|
|Plant Type||Deciduous flowering shrub|
|Mature Size||5–10 feet tall, 6–10 feet wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Medium moisture, well-drained soil|
|Soil pH||5.0–8.0 (acidic to alkaline)|
|Bloom Time||April to May|
|Hardiness Zones||4–9 (USDA)|
|Native Area||Mountainous regions of China and Japan|
|Toxicity||Toxic to people and pets|
Japanese Rose Care
Japanese rose prefers to be planted in a loamy, well-drained soil in part shade, though it has a good tolerance for any soil type, and will also tolerate full sun. If you have dense soil, thoroughly amend it with compost, peat moss, or another organic material as you plant. Dense soils may cause root rot in this plant.
Japanese rose is largely a carefree shrub but will require frequent removal of suckers if you want to prevent the shrub from spreading.
Grow this bush in part shade for best flower production. It is one of the most shade-tolerant of the deciduous flowering shrubs when it comes to flowering. Japanese rose will do fine in full sun, but too much bright sun causes the flower color to fade quickly.
Japanese rose prefers loamy soil and is not overly fussy about soil pH. It will also tolerate poor soils but will perform better in soils enriched with organic material. The ground should be kept evenly moist around Kerria japonica, but it doesn't like soggy conditions. Lightly mulching will help conserve soil moisture.
Japanese rose shrubs need regular water, but take care not to overwater, especially in dense soils. This shrub has a good tolerance for short periods of drought.
Temperature and Humidity
Japanese rose shrubs thrive in all climate conditions over its hardiness range, USDA zones 4 to 9. In the southern part of the range, it will appreciate deeper shade.
Fertilize Japanese rose shrubs lightly in spring, using a slow-release fertilizer. Organic mulch will also help feed the plant.
Japanese Rose Varieties
There are several popular named cultivars of Japanese rose. Among the popular varieties:
- Kerria japonica 'Plentiflora': This is a popular double-flowered cultivar with 2-inch pom-pom flowers. It grows 8 to 10 feet tall.
- K. japonica 'Picta': 'This variety is a low-growing, spreading cultivar that grows only 2 feet tall and wide. It has wide, rose-shaped flowers and grayish-green leaves with white edges.
- K. japonica 'Albescens': This cultivar has creamy yellow 2-inch flowers and grows 4 to 5 feet tall. The foliage turns pale yellow in fall.
- K. japonica 'Golden Guinea': This single-flowered cultivar has yellow flowers roughly the size of a gold coin (2 1/2 inches). It grows 6 to 8 feet tall.
- Kerria japonica 'Simplex': 'This cultivar is known to rebloom, and it has bright green stems that provide winter interest to the landscape.
Pruning Japanese Rose
This plant blooms on old wood (previous season's growth) in early-to-mid spring. If you must prune for shape or control the height, do it just after its spring flowering is over. A second flowering later in the growing season is not unusual, but it is too late to prune at that point. Prune out dead branches as you find them. Old plants in need of rejuvenation pruning may be cut down to ground level.
Japanese rose spreads by suckering; remove these suckers as they appear if you wish to control its spread. The main problem with this plant is that it spreads so vigorously, so stay ahead of it with regular sucker removal.
Propagating Japanese Rose
This shrub is best propagated by rooting softwood cuttings:
At the beginning of summer after the flowers are gone, snip a 4- to 5-inch cutting from the terminal end of a branch. Make the cut just below a leaf node. Trim away all the leaves from the bottom half of the cutting. Dip the end of the cutting in rooting hormone.
Plant the cutting in a small pot filled with an equal mixture of perlite and sand, or perlite and peat moss. Place the potted cutting in a large plastic bag or under a plastic dome, and place it in a location that received bright indirect light. Mist the cutting daily.
Roots should begin to develop in 4 to 6 weeks. Once you detect roots, allow the cutting to grow for another month, then transplant into a larger pot, if necessary. Continue growing the plant until the following spring, at which time you can plant it outdoors.
Although it is an overall tough specimen, Japanese rose can become infected with twig and leaf blight, a disease caused by the Blumeriella kerriae fungus. The symptoms are small red-brown spots that gradually coalesce and cause leaves to turn yellow and brown before falling. Bi-weekly sprays of chlorothalonil fungicide will reduce spread of the disease, but badly affected stems should be pruned away.
This plant has no serious pest enemies.