Answer: Dogwoods often take a year or two or three to settle in after transplanting and regain strength enough to bloom. They may also need to reach a certain amount of maturity, say four or five years, in order to bloom.
Improper pruning can also remove flower buds; keep in mind these trees bloom in late spring to early summer, well after the native dogwoods and as a rule require little to no pruning.
However, after nine years, these more common reasons would not seem to explain away the delay.
Insufficient sun can be a cause of lack of bloom or very light bloom. The kousa dogwoods actually prefer more sun than the native dogwoods typically do, so if yours are in a shady area this might be the cause. After nine years in place, I would be hesitant to try to move them to a sunnier spot, however.
If the trees have not grown much over the nine years, the
I would begin to suspect that there is some type of cultural problem, perhaps that the original roots have not grown out into the surrounding soil as they should, or some other reason such as soil or exposure or excess wind or other adverse conditions is causing them not to thrive.
At that point, I would suggest you contact a local expert for consultation where they can evaluate the trees and their poor growth and lack of bloom. Your county extension might be able to help, or you might wish to consult with a professionally trained and certified arborist who is familiar with specialty ornamental trees such as these. I'm sorry I can't be more specific.
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