Dogwoods like poor soil, so I would be extremly cautious about fertilizing them with chemicals or even much with organics, and most especially in this heat. My favorite fertilizer is Composted Manure that you buy in 40 pound bags at the Big Box Stores for about $1.50 a bag. I spread about an inch or two over all my beds every fall or spring, and work it into every planting hole. It is good for the soil, good for the worms, etc. and will never burn your plants. If my plants (rarely) need a boost in addition to that, I use fish emulsion. It's better than any chemical I have ever tried.

Thank you very much for the response. I am now much better informed. Your advise will be well applied. We do not have Big Box stores here but, I'm sure I can find the manure you speak of.
Cheers

As a chemist and an avid gardener I would like to point out the sillinest associated with fertilisers. ANY fertiliser is fine as long as it is applied in small amounts and not as a heavy dose. The saying"if a little is good then a lot is better" has NO place in horticulture As long as a fertiliser contains the elements nitrogen, phosphorus, potassium, and some trace elements, it is supremely satisfactory. The so-called organic fertilisers release these components identically to the so-called chemical fertilisers...they just cost more for lower concentrations of the essential elements. Go find yourself a good text on plant physiology;it might be a real eye-opener!!!