Tree care doesn't have to be a highly technical or complicated subject, since most trees fend for themselves pretty well. By following some "tree basics" it's easy to promote healthy growth in trees. Since most individuals will be dealing with existing trees in the landscape, this page will address tree care from the long term care perspective, instead of the care of newly planted trees.
One of the most basic principles of tree care is "do no harm." Vigorous trees appear to be invincible, and individuals are often negligent without even realizing it. A good example would be the repeated use of a string line weed-whacker around the base of the tree to keep the grass trimmed away from the trunk. At first glance, it would appear that the plastic line couldn't possibly harm a "tough" tree trunk. But when you consider the velocity of the line, and the living tissue just below the tree's outer bark, you realize that repeated use of a stringline trimmer can open trunk wounds and subject the tree to destructive, invasive pathogens. Therefore, be careful using weedwhackers around tree trunks, or better yet, create a protective mulched area around the base of the tree so weedwhacking next to the trunk isn't necessary.
Don't add soil fill over an existing root zone unless it is absolutely necessary. Even though placing a couple inches of soil over a bumpy root system in the lawn won't usually harm a tree, it's better yet to create a mulched area or groundcover planting in the tree's root zone.
Don't leave tree supports and guy wires wrapped around new trees too long. Check them periodically, especially during the growing season to ensure they aren't girdling (choking) the new tree. Tree supports are only left on 1-year unless there are special circumstances.
Don't leave branch stubs when trimming off branches. Branch stubs provide an excellent entry root for destructive insects and disease pathogens. At the same time, cutting a branch too close to the tree trunk can remove the "branch collar," which provides a degree of natural protection to the open wound. Trees actually have protection ability built right into the branch collar. Therefore, the second "don't" in this paragraph is: Don't paint branch cuts -- the tree already has natural protection from the branch collar and painting is unnecessary, even undesirable.
Don't "TOP" trees with "hat rack" style trimming techniques. If a large tree is planted in the wrong spot and needs this drastic method of trimming, it's better to remove the tree, completely grind out the stump and plant a tree which won't grow so large. Topping creates large branch wounds, subsequent weak growth of fast growing sprouts and basically ruins the natural structure of the tree FOREVER.
Don't trench close to a tree trunk for utility lines. Since most tree roots are in the top 24-inches of the soil, digging a utility line trench between the trunk and the branch tips will effectively remove a large percentage of the tree's roots, causing problems with water and nutrient uptake as well as stability.
Don't plant fast growing trees (Silver Maple, Poplar, Willow, Bradford Pear, etc) that will rapidly become problems in the future.
Don't use herbicides in a tree's rootzone which leach down through the soil and to be picked up by the tree's roots, causing damage to the tree. Many dandelion and broadleaf weed killers are known to leach, while glyphosate is more quickly immobilized in the soil.
Don't spray any kind of weed killer on the trunk, branches or exposed roots of a tree, while keeping in mind that "thin barked" trees (like beech) can be especially sensitive to damage from weed killers.
Thoroughly water a tree's entire root zone during periods of drought with the equivalent of one-inch of water, once every week or two, depending on soil type. Apply slowly to prevent runoff.
Fertilize once a year in springtime with a 2-1-1 ratio fertilizer, following label instructions.
Watch for any developing insect or disease problems and address problems early. Follow IPM (Integrated Pest Management) guidelines with all treatments.
Follow proper pruning guidelines and techniques.
Use caution around trees with de-icers and herbicides. Some lawn herbicides can leach into the root zone and be picked-up by tree roots, causing tree damage.
Plant improved varieties of trees. Selected varieties have more resistance to common disease problems.
Remove undesirable, problem trees. Plant desirable trees in their place.