Chinese dogwood (Cornus kousa var. Chinensis), a deciduous, flowering shrub or small tree, is native to Japan, Korea and China and hardy at U.S. Department of Agriculture plant hardiness zones 5 through 8. As a general rule, the magnitude of the main structure of this tree is four to seven times the area covered with its crown. Chinese dogwood includes a 15- to 30-foot crown, so its roots could cover an area from approximately 185 to 660 square feet.
Planting
Most Chinese dogwoods are offered in nursery pots or even “balled and burlaped,” using their roots encased in a ball of dirt which is then wrapped in burlap or some similar material. To allow for root growth, it is important to either cut or removed large slits in the burlap wrapping stuff. If you don’t do so, the plant’s roots grow in circles instead of growing outward. Finally this weakens and kills the young tree.
Where to Plant
Plant young dogwoods in sunlight to light shade with a eye on the mature size of the roots and crown. If the dogwood is meant as a street tree, make sure the planting strip between the curb and the sidewalk is wide enough to accommodate the roots. If the strip isn’t wide enough, then plant the dogwood on the opposite side — property or house side — of this sidewalk. The planting hole should be at least twice as wide as it is deep to permit for root growth.
Root Growth
Most Chinese dogwood roots, like those of most trees, which are at the top 18 inches of dirt. Due to this, it is very important to mulch and water the trees, especially when they are young. Watering is best done by drip irrigation, which reduces water evaporation. Mulch, that insulates and conserves soil moisture, should be spread in at least a 3-foot-wide circle around, but not touching the trunk. Mulch thickness should be 3 to 4 inches.
Care
When the Chinese dogwood is established, good root care will ensure it continues to be healthy and blossom freely. Avoid piling additional top soil around the base of this tree. When digging inside the root zone — for example installing garden plants — plant in pockets between roots, rather than cutting through roots. Don’t cut through roots to set up walkways or other hardscaping. Roots that are severed or otherwise limited cannot support the tree adequately or hold the dirt well enough to stay upright in strong winds.