For more information on cultural issues read Abiotic Problems of Trees or contact a certified arborist to help identify and manage the problem.
Tree health and growth depend on adequate water. When trees are unable to take up enough moisture they may begin showing signs of stress and become more susceptible to insect and disease infestation. Watch for leaf droop and drying foliage, especially at leaf edges.
Extremely hot, windy weather can cause wilting or browning of foliage, even when soil moisture is normal. If severely hot, dry weather is short lived, established healthy trees can recover on their own. For newly planted trees and during a prolonged drought for established trees, watering should be done to help reduce the effects of stress.
To check soil moisture in the tree's root zone, push a long screwdriver or similar object into the soil. If soil moisture is adequate, it should be fairly easy to push the screwdriver into the ground 6 to 8 inches. If the ground is dry and in need of watering it is typically very difficult to push the screwdriver in beyond a couple of inches.
Deep, thorough watering will provide the most benefit to trees. Excessive watering, especially in heavy soils, may force air from the soil and cause roots to suffocate. Soil should be kept moist but not soggy.
Infrequent deep watering, equivalent to 1 (or approximately 25 gallons of water) or 2 inches of rain for newly planted trees, is most beneficial for trees because it promotes healthier root systems, which are better able to sustain trees during times of drought. Frequent shallow watering will only favor grass growth.
Mulch helps conserve soil moisture and moderates soil temperature, so applying a 2- to 4-inch layer of wood chips or bark, will benefit your trees during hot summer months.
Spread mulch evenly around your tree and be sure the mulch does not pile against the tree's trunk, as this can lead to disease problems. Don't mulch with rock or use plastic sheeting under the wood chip mulch. Mulching also helps with separation between turf and trees. Increasing the distance between the tree trunk and turf will help prevent damage from mowers and weed trimmers.
Mulch near (not against) the trunk should be approximately 1 inch deep, while mulch can be up to 4 inches deep toward the edge of the mulch ring. Don't allow mulch to rest directly against the trunk of the tree as this can encourage circling roots.
Newly planted trees can benefit from staking, which can help trees that are tall and leggy or those that are planted in high-wind areas establish healthy root systems. Smaller trees or trees planted in protected areas may not need to be staked. Trees are staked to anchor the root ball, not to eliminate movement of the stem or canopy.
A common misconception is that trees need to be fed. Trees make their own food through photosynthesis. Fertilization provides nutrients, not food to plants. In fact, fertilizing your tree can do more harm than good. Overfertilization of nitrogen in particular promotes aphid and spider mite populations and can stress trees so that they become more susceptible to canker diseases and insect borers. Unless your soil has a known nutrient deficiency that has been identified by a soil test, do not fertilize your trees. Typical fertilizer applications to the lawn generally meet the nitrogen requirements of landscape trees without the need for additional fertilizer.
Micronutrients such as iron and manganese are sometimes deficient in soils, but more often are tied up by poor soil conditions. Organic mulches such as wood chips improve soil fertility by adding nutrients to the soil and improving conditions for nutrient uptake by tree roots.
Keep in mind that root damage, soil compaction, wilt diseases and insect infestations can cause symptoms similar to those of heat and water stress. If the tree does not respond to watering it may be an indication that something else is wrong.
Young tree pruning: http://www.treesaregood.com/treecare/pruning_mature.aspx
Mature tree pruning: http://www.treesaregood.com/treecare/pruning_young.aspx