Dogwoods bloom on old wood, setting the flowers for the following year during the summer. They rarely need pruning, except to remove crossing or rubbing branches, water sprouts, or dead/dying branches. They will bloom more in sunny locations, but too much harsh sunlight can damage the leaves and stress the tree.
The biggest problem for dogwoods is a fungal disease called dogwood anthracnose, which can cause branch dieback and even kill entire trees. It is spread by water droplets carrying the pathogen. If you have an infected tree, you will start to see symptoms in mid- to late-May, when leaf spots will appear, and cause irregular-shaped holes in the leaves with purple or tan borders. You may also see tan spots on the flowers. This disease is common in nature, so you should never try to transplant a dogwood tree from the wild into your yard. Luckily, plant breeders have developed cultivars that are resistant to dogwood anthracnose, as well as several other problems like powdery mildew, that dogwoods often have. C. ‘Appalachian Spring’ was the first cultivar that was developed, but today there are several. There are also hybrids developed from crosses with Chinese dogwoods which are naturally resistant.