Kerria (Kerria japonica), a native Chinese shrub, grows in U.S. Department of Agriculture plant hardiness zones 5 through 9. Reaching 6 feet tall and 8 feet wide, the plant displays small yellow rose-like blossoms in the spring and throughout the early summer, against green triangular leaves that turn yellow in fall. Double-flowered Japanese rose (Kerria japonica “Pleniflora”) is a taller variety of kerria reaching 10 feet tall and wide. Digging up the suckers and transplanting them is the easiest form of propagation for kerria shrubs. The best time to transplant is early spring, while the shrub is still dormant.
Brush the soil away from the base of a kerria sucker and find the location of the root connecting it to the parent plant. Severe the connecting root with a pair of pruning shears. Dig up the sucker with a shovel, obtaining as many roots as possible. Place the roots in a bucket of water, but do not keep them in the water for longer than an hour.
Loosen the soil in an area with full to partial sun exposure. Remove all grass, weeds and rocks. Dig a hole in the center of the planting area twice as wide as the roots and only as deep to plant the young kerria shrub at the same depth that it was previously growing.
Create a mound of soil in the bottom of the hole and spread the roots down the sides of the mound without bending them. Fill the hole with soil, three-quarters full. Fill the hole with water and let it drain away. Finish filling the hole with the rest of the soil.
Spread a 1- to 2-inch-layer of organic mulch over the root ball to help retain soil moisture and reduce weed growth. Do not pile the mulch on the trunk, because it encourages trunk rot.
Water the newly transplanted kerria shrub deeply. Continue to water each week it does not rain for the first year, until a new root system is established. During hot weather, the shrub may need watering twice a week.