Celestial dogwood, known botanically as cornus rutdan, is a late spring blooming hybrid varietal that throws whitish-green bracts commonly considered to be the flowers. Celestial dogwood, like all dogwoods, thrive in a partial daily shade or filtered shade exposure and is best planted as an understory tree. It is hardy in USDA zones 5 through 9 and performs best in an acidic soil with abundant water and sparingly applied fertilizer.
Select a planting location that affords the dogwood partial shade of at least four to five hours per day or filtered sunlight all day long. Choose a site that is under a canopy with at least 6 to 8 feet of growing space for the tree.
Prepare the planting soil by tilling up a plot of soil at least 2 feet deep and 6 feet wide. Remove any rocks or hard clods of clay and amend the soil with a few pounds of quality compost and peat moss to raise the acidity. The large preparation area is to help the dogwood's shallow spreading roots to easily penetrate and establish themselves. Dig a hole at least twice the diameter and just as deep as the root ball.
Place the tree in the hole so that the top level of the root ball is level with or just sitting above the surrounding soil. Fill in soil underneath the root ball to achieve this. Back fill the remaining soil around the root ball to secure it upright in place without completely compacting the soil.
Create a watering moat 2 feet out from the trunk with the remaining displaced soil and fill with water. Allow the water to percolate completely into the soil before filling the moat for a second time. Keep the soil from the trunk out to the drip line evenly and consistently moist for the first year after planting.
Mulch around the base of the tree after watering with at least a 2-inch thick blanket of shredded pine bark or pine needles. Lay the mulch from the trunk to at least 2 feet beyond the drip line. Replenish the mulch each year as it degrades into the soil.