The following question was sent to the P&PDL diagnosticians here at Purdue University:
Question: I have 6-year-old flowering dogwood trees that have never bloomed. The foliage looks healthy each year. What do you suggest?
Answer: It does take a dogwood a few years to become established, and we don't make the job any easier for them. Drive through Southern Indiana and notice where the dogwoods are growing. They're nestled into the edge of the woods where they receive shade and protection from larger trees above. We often plant them out in the middle of our yards, in full sun and clay soil, and expect to replicate their performance in nature. Help the tree feel more at home by removing turf from a circle around the trunk and adding a layer of mulch, at the very least.
There are many possible reasons for a lack of flowering in plants, including age, light, excess nitrogen, temperature and pruning. Make sure your plant is receiving a half day of sunlight. Fertilizers high in nitrogen, like most turf fertilizers, encourage foliar growth at the expense of flowers, so keep these away from the plant. Only prune just after flowering, or in your case, just after other dogwoods in the area flower, so you don't remove next year's buds. Finally, provide 1 inch of water per week, supplementing rainfall if necessary.
There is one more possibility. Dogwoods are often shipped into the Midwest from southern sources. These plants are not adequately hardy in northern areas. Many flowering dogwoods in the Midwest have minimal flower production, which is caused by this lack of flower bud hardiness. If possible, ask the nurseryperson or garden center where the trees are grown to save yourself disappointment three to five years down the road when the trees show limited flowering.
-Beverly Shaw, Advanced Master Gardener, Purdue University