If they are growing extremely fast, sometimes they grow to the exclusion of flowering. Patience is the remedy there. But do check sunlight, you may have to move the tree if you ever expect blooms. Back to top I recently gathered some of the red fruit or seeds from my dogwood trees. I have heard you can put these in small plastic bags filled with peat moss and if left in the refrigerator all winter, can plant them in the spring.
Dogwoods grow readily from seed.
Simply put moist peat moss and seeds in the plastic bag not water, and then place in the refrigerator. This cool moist period is called stratification. After a couple of months of this, the seeds can germinate. You can also stratify the seeds outside in the ground. Remove the outer red pulp, till an area of soil and plant the seeds.