Regardless of the type of soil in which they are planted, dogwoods need faithful watering when they are first planted, during droughts and in late fall before the ground freezes. They are extremely sensitive to drought. If they are planted in healthy soil that has lots of organic matter in it to hold moisture, you probably only need to water during dry periods. Dogwoods in poor soils will need more water. Run your drip irrigation system orsprinkler for as long as it takes to deliver 1 inch of water whenever rainfall is less than that 1 inch per week. Always mulch the soil under the tree to reduce evaporation of moisture from the soil.
Young dogwoods that are established a year or so at their new site benefit from a spring application of an all-purposeslow-acting granular fertilizer 6 66 200 with a large proportion of water insoluble nitrogen (WIN). After the leaves appear on the dogwood, sprinkle fertilizer on the soil around its trunk out to 1-1/2 feet beyond the tips of the branches. Use about 1/2 pound per 1/2 inch of trunk diameter measured at its base. If you keep your dogwood tree mulched year round with 2 to 4 inches of organic material, you can stop fertilizing in two or three years.
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A layer of organic mulch spread in a circle on the soil under the dogwood tree protects it from injury by lawnmower or weed trimmer equipment. It offers many other benefits as well. Not only does it keep the soil moist and discourage weeds, but as it gradually decomposes it adds valuable organic matter to the soil in the root zone. It harbors beneficial organisms that prey on pest insects and their eggs, holds soil moisture and insulates the soil against extreme temperature changes in the winter.
Spread 2 to 4 inches of an attractive organic material such as chopped leaves, shredded bark or wood chips alone, or combined with peat moss 6 75 100 to hold moisture better out to the tips of the branches (dripline) or beyond. Keep the mulch about 6 inches away from the trunk to avoid stem rot and rodent damage. Do not mulch with unchopped leaves because they mat together, preventing water from soaking into the soil. It's best to hand-pull any maverick weeds growing near the tree to avoid damaging shallow roots. Keep the mulch on year round, renewing it when it is less than 2 inches deep.
For more information see the file on Using Mulch
Dogwoods require little pruning, except to encourage one central trunk when they are young. Otherwise, prune as needed to remove dead wood and to eliminate root suckers. Do this when the tree is dormant during the winter, or soon after it flowers in the spring. If your tree suffers dieback as described in the problems section, routinely prune dead wood at tips of limbs back to healthy wood that is producing foliage.
For more information see the files on Pruning Shade and Flowering Trees and Choosing Pruning Tools