Keys to Successful Tree Planting
Too many trees are killed due to improper planting technique and inadequate care after planting. There's no need for anyone to have a brown thumb, or to be afraid to plant because "everything I plant dies". What can you do about it?
When to plant
Trees that have been dug from the ground (or grown in a container) can be planted at any time of the year, but the optimum periods are early March through late April (before leaves grow), or mid-October through late November. These are the times when trees are dormant, and they have less demand for water.
However, if you are able to water (see below) then there's no reason not to plant later in the spring or in late summer. Trees can be planted in July and August with success if you are able to water regularly.
Digging the hole
Standard procedure dictates that the planting hole be dug at least twice the width of the rootball. However, studies have shown that a larger hole does not lead to greater survival, or quicker growth. While the width of the planting hole makes little difference, planting trees too deeply is the leading cause of death, though it can take a year or longer for the tree to die.
There is no question that the planting hole should not be any deeper than the depth of the rootball, and in fact, it is better to dig the hole a few inches less than the root's depth. A shallower hole allows the rootball to sit at a level slightly above the surrounding ground so that drainage is improved, in particular in clay soils. Do not dig a deeper hole and backfill soil to the proper depth. The loose soil will compact under the weight of the tree and will sink too deep.
Soil amendments and backfill
Most people assume that their clay soil must be amended with compost or topsoil for the tree to have a chance for survival. Instead, numerous studies have shown that too much rich soil holds excess moisture, and can be detrimental to a tree's health. It is better to use too little soil amendment rather than too much, and no amendment at all is fine for planting trees. Use no more than a 25% mix of soil amendment to existing soil, and the amendment and existing soil should be mixed thoroughly.
Place the tree in the center of the hole. Backfill several inches of soil and firm it with your boot so that the tree is straight. When planting a tree the burlap covering the rootball should not be removed unless it is a nylon burlap, though that is rarely used today. Strings that wrap around the tree's trunk, and burlap on the top of the rootball should be cut away. The wire basket that surrounds the rootballs of larger trees should be removed if it can be cut off without damaging the rootball.
With the tree stabilized by several inches of soil, and string and burlap cut, resume filling the backfill a few inches at a time, firming the soil (but not stomping) as you go. With each increment you can fill the hole with water as you go. This will assure that water reaches more deeply into the hole for the initial watering, and it helps to firm the soil surrounding the rootball.
When the backfill is complete any remaining soil is used to build a slight lip, so that the top of the soil appears like a dinner plate. This will help to hold some moisture when you water, and direct the water to the rootball rather than encouraging it to drain away. No soil is placed around the tree's trunk, and in fact there are times when loose soil has been graded against the trunk by the tree nursery and the root flare (where trunk begins to curve to roots) must be dug out to be slightly above grade.
Once the tree has been planted an organic mulch (bark, leaves, or compost) should be applied to a two to three inch depth. Care should be taken that no mulch is piled against the trunk. The mulch will help to conserve moisture and keep weeds down. Deep mulch against the trunk is referred to as a "mulch volcano", and can be detrimental to the tree's health.
Trees develop stronger roots if they are not staked, and are allowed to sway slightly in the breeze. However, if a tree is planted in a windy location it is better to stake the tree rather than having it blow over and injure the roots.
Trees can be staked with two tall (usually 6 foot) stakes or three shorter (often 2 foot) stakes. Wire or plastic is used to secure the tree to the stake. If wire is used then the tree's trunk should be protected with a section of rubber hose to prevent the wire from rubbing. Stakes should be removed no later than a year after planting, and often can be removed much sooner.
Fertilizing, watering, and other care after planting
Most soils contain adequate nutrients for many years of a tree's growth. Fertilizer is more important for annuals and perennials, but is not required for trees. If you decide to fertlize to encourage more rapid growth, fertilizer spikes encourage roots to grow towards the spike, and fertilizer that is broadcast is better. Do not fertilize trees annually since this will encourage weak wooded growth that is more susceptible to disease and to breaking.
Newly planted trees should be watered regularly until they are established. How much water, and frequency of watering depends on weather conditions. Generally one inch of water each week is recommended, but it is better to water deeply and less frequently than to water every day. Even in the heat of summer every day watering is not ideal.
The best watering method is some form of drip irrigation, or watering with a garden hose at only a trickle of water. This allows water to sink in, rather than draining off. A hose set at a trickle of water placed near the tree's trunk for a half hour to forty-five minutes will water quite deeply, and doing this twice a week for the first four to six weeks after planting will assure that the tree will get off to a good start. After this period you should be able to cut back on watering, unless temperatures are high and rainfall low.
Other tree care is usually not required. Most trees do not require regular pruning, though crossed branches and y-shaped crotches can be problems if not correctly while trees are young.