Answer: The best way to figure out how to fertilize the dogwood and with what is to run some basic soil tests and find out what kind of fertility already exists naturally in the soil where they are planted. Then, based on the results, you could figure out what, if anything, you need to do. Your county extension should be able to help you with the tests and interpreting the results.
In general, you could use a mild, slow release, complete, granular fertilizer for acid loving plants such as Hollytone. Read and follow the instructions on the label, and do not exceed the recommended amounts because too much fertilizer is not better than too little -- it can even "burn" the roots. Dogwoods are naturally slow growing and do not really need a whole lot of nutrients to thrive.
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