Background

Broadly speaking, there are two types of trees -- deciduous and evergreen. Deciduous trees shed their leaves in the fall and go dormant in the winter, while evergreens retain their foliage throughout the year. Evergreens may be further subdivided into conifers such as spruces, firs and pines, and broad-leafed species like southern magnolias and camphors. Within these broad categories, trees exhibit countless variations in height, canopy shape, foliage, bark texture, wood density and longevity, all of which should be considered before you decide what kind of tree to plant in your lawn. Once you've chosen the right tree, here are some tips to planting and caring for it to keep it healthy for years to come.

How to Care for Trees

Planting. Though you can plant a tree from balled-and-burlapped or containerized stock just about any time the soil is workable and reasonably warm, spring should be your first choice for most tree species, followed by fall, then summer. If you elect to plant in the summertime, however, make sure you're willing to keep up with the watering. Your young tree will need it!

Select a planting site where the newly established tree will have get the light (or shade) and space it needs. For large shade trees, this means plenty of direct sunlight, as well as plenty of room to spread its canopy above the ground and its root system below. The classic shade trees like oaks, maples and elms need to be very widely spaced (and kept away from the house!) due to their extensive canopies, while columnar trees such as poplars and grey birches may be grouped closer together. Understory trees, like dogwoods, redbuds and serviceberries can be planted in either sun or shade. They'll bloom more abundantly in sun, but may scorch in the hot summer sun.

Make sure that your planting site is level and drains well. If your chosen site requires leveling, do so prior to planting as the roots of a growing tree can easily become smothered if you bury them too deeply beneath soil that has been added later.

• If the soil of the planting site is overly acidic or alkaline for the type of tree you've selected, amend it beforehand by adding lime (to raise the pH of acidic soil) or elemental sulfur (to lower the pH of alkaline soil) as necessary. (In the long run, it would be better to choose a tree that likes the existing conditions, rather than maintaining an ongoing program of trying to modify those conditions.)
• Dig a hole twice as wide and slightly less deep as the rootball of the tree, angling the walls of the hole outward toward the top. When in place, the top of the rootball should be slightly above the level of the surrounding soil.
• Position the tree in place in the hole before removing the container or burlap. Cut away plastic pots and gently slide the plastic from under the tree. For balled-and-burlapped trees, cut twine and fold burlap into the hole. The burlap will decompose in time, and attempting to remove it can damage the rootball.  Be sure to cut and remove any plastic twine, since it will not decompose and could choke roots as they grow.
• Inspect the rootball and snip off or pull away any roots that are circled, matted or tangled. Also, trim any dangling root ends to prevent them from becoming bent or tangled when the rootball is placed in the hole.
• Many arborists recommend reusing native soils instead of replacing them with organic components that are significantly different than the surrounding soils. If you want to improve the backfill soil you've dug from the hole by amending with rich, organic materials such as compost or pre-packaged garden soils and planting mixes, mix one part garden soil to two parts native soil. If planting in spring, add a complete, slow-release fertilizer to the backfill soil. Backfill the planting hole to the level of the top of the rootball, sloping the soil away from the trunk to the level of the surrounding soil.
• Create a 2-4 inch high lip around the perimeter of the planting hole to act as a catch basin for water.
• Fill the collection basin with water until the ground is loose and muddy in order to eliminate air pockets. If the tree needs to be re-positioned slightly, do so at this time by gently jiggling it into place.
• Mulch around the young tree to retain moisture and prevent encroachment by weeds and invasive lawn grasses. Also, water frequently until the shrub has become well established, especially if the foliage shows signs of withering or curling during the heat of the day.

Feeding. Regular feeding can not only keep your trees flowering and growing vigorously, but specially formulated plant foods can correct pH imbalances that can lead to nutrient deficiencies. Apply the appropriate formula of slow-release plant food at planting time and periodically through the growing season. If you don't use a slow-release plant food,  feed weekly with all-purpose water soluble plant food. To feed large areas, use a hose-end feeder.

For flowering shrubs, switch about 4 weeks before the flowering period to a high-phosphorus water soluble plant food specially formulated for flower bud development.

For acid-loving trees like dogwoods, evergreens, magnolias and others, use an acidifying water soluble plant food.

Watering. Newly planted trees will need extra attention to watering through the first season, especially, and to a lesser degree over the first few years until roots are well established. Water weekly through the first season, and make sure the plant receives an inch of water each week through rain or irrigation thereafter.

Pruning. Pruning is a complex subject, and difficult to deal with in a generic overview, since different trees have widely ranging prunings requirements. Most trees don't require extensive pruning once established.  Dead, diseased or damaged limbs of any tree or shrub should be pruned immediately at any time of year to protect from additional insect or disease damage.

Some plants, particularly many flowering ornamental plants like cherries, crab apples and hawthorns, produce abundant water sprouts and suckers. Water sprouts are straight, fast-growing shoots that generally grow vertically from stems, while suckers initiate from roots at the base of the tree. These should be removed since they won't flower or exhibit other desirable characteristics, and draw energy from the rest of the tree. Similar sprouts and shoots that grow on contorted or weeping varieties should also be pruned.

One form of pruning that should NEVER be performed is a practice called "tree-topping." This was a popular practice decades ago that has persisted in some areas, in which major portions of a tree canopy are removed. The practice is extremely hard on a tree, destroys it natural appearance, and can actually make the tree more dangerous, because the new limbs that grow are very weakly attached and subject to wind damage. Professional arborists can reduce tree size just  as effectively by selectively "lowering" the canopy, with much less harm done to the tree, both aethestically and physically.

Here are some other considerations regarding tree pruning:

• Before pruning, check with an arborist or nursery professional to determine the best time to prune. Some trees, like elms and oaks, are more prone to insect infestation and resulting disease if wounded (pruned) at certain times of the year.
• When pruning, be sure to keep your pruning clippers and saw blades as sharp as possible. A dull cutting edge results in frayed, ragged ends that can admit diseases and fungi more readily. Sterilize your clippers after each cut, especially if removing diseased wood, with alcohol or a bleach/water solution. A disinfectant aerosol also works and is easier to carry around than open liquid containers.
• When removing side branches, make the cut as close to the main stem as possible. Longer stums will die back, creating inviting entry points for insect and disease.
• Large branches should be removed using a "three-cut" method to avoid stripping bark from the tree as the branch falls. First, make a cut under the branch about 12 inches from the trunk. Second, cut through the branch from the top at a spot an inch or so to the trunk side of the first cut. Third, remove the remaining stump just outside of the "branch collar," the area of raised bark at the union of the branch and trunk.  

Insect and Disease Control

It's nearly impossible to summarize in a general discussion the multiplicity of diseases and insects that affect trees. Some species are virtually disease free while others are magnets for any number of pests. Before planting some shrub you fell in love with on a national gardening show, ask a local nursery professional if it's a good choice for your area.

Fungus diseases in trees are usually not practical to treat because of their mature size. Diseases on younger trees can be prevented and controlled with a regular fungicide treatment program. These treatments should begin before disease conditions exist, and continue faithfully until those conditions no longer are present.

Insect pests common to a variety of shrubs include aphids, whiteflies, scale,  leafminers, leaf hoppers, and a host of borers. Insect pests can not only do damage directly, by feeding on leaves and sucking juices or burrowing into the wood, but they can also be vectors (carriers) for plant diseases, or create injuries that allow diseases easier entry into plant tissue. After identifying the insect pests, leaf-chewing and leaf-sucking insects can be controlled with insecticidal soap, neem oil, pyrethrin or other insect spray. Borers represent a more serious threat, and are more difficult to treat, since they are usually protected in the wood. Consult a professional arborist is signs of borer insects are present.

Propagation

Most trees can be grown from their seeds, or from stem cuttings taken from the parent plant. Seeds can sometimes be collected and planted directly with excellent results (anyone in the proximity of an elm tree or silver maple knows how easily their seeds sprout.) Others require various processes to bring about germination. These processes can be as simple as storing the seed in a refrigerator for a few months to more complicated practices of scratching, scoring or treating the seed service with acids. If you've tried to grow trees from seeds without success, look for information in books, on the internet or from a nursery professional to determine the specific requirements for germination of that specific plant.