Japanese rose (Kerria japonica) is a deciduous flowering shrub that bears chrysanthemum-like yellow flowers in spring and sometimes additional blooms later in the summer. The bark and branches are also of interest. The main branches on the double flowering type arch gracefully to a height of 8 to10 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.
|Botanical Name||Kerria japanica|
|Common Names||Japanese rose, Japanese marigold bush, Easter rose|
|Plant Type||Deciduous flowering shrub|
|Sun Exposure||Japanese rose, Japanese marigold bush|
|Soil Type||Medium moisture, well-drained soil|
|Soil pH||No preference|
|Bloom Time||April to May|
|Hardiness Zones||4 to 9 (USDA)|
|Native Area||Mountainous regions of China and Japan|
How to Grow Japanese Rose
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. It is largely a carefree shrub, but will require frequent removal of suckers if you want to prevent the shrub from spreading.
There are no notably serious insect or disease problems with Japanese rose, although they can be susceptible to leaf spots, cankers, blights, and root rot.
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.
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.
Pruning Japanese Rose
This plant blooms on old wood (previous season's growth) in early-to-mid spring; prune 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.
Varieties of Japanese Rose
- 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.
Toxicity of Japanese Rose
The leaves of Japanese rose contain small quantities of hydrogen cyanide. Small doses are not harmful, but heavy ingestion has been known to cause respiratory failure or even death. But it is quite rare for the leaves to be consumed in harmful quantities.
The shade tolerance of Japanese rose gives you the option of having a deciduous flowering shrub in a partially shaded area, while the profusion of blooms on the bush makes it a spring standout. Kerria japonica is not a good choice for a formal hedge, because excessive pruning ruins its beautiful natural shape; but there is no reason the plant can not be used in a looser, informal hedge.
Do not underestimate the importance of Japanese rose's attractive branches, which provide much-needed visual interest for the winter landscape. In this sense, Japanese rose branches are similar to red twig dogwood and yellow twig dogwood. Choose a background against which the branch color can be displayed to optimal effect; for example, Japanese rose's Kelly green stems look terrific against a barn-red shed.
This is an attractive flowering shrub for shady woodland gardens or shrub borders, and also works for foundation plantings. It is a natural choice for wild, naturalized areas where the plant can be allowed to sucker and spread.