1. Choose the proper planting time.
A. In warmer climate zones (about zone 5 or 6 and higher) where the ground doesn't commonly stay frozen through most of the winter, most trees and shrubs can be planted at anytime between early to mid fall (just before or around the time of leaf drop) and early spring (before bud-break) as long as the ground is not frozen. Early to mid fall is probably the optimal time for many trees and shrubs because the root system has a longer time to become established before the plant has to deal with the stress of summer heat. Potted plants which are not potbound, and therefore do not require significant root manipulation, can be planted even in mid summer without much risk. Bare-root, balled-and-burlaped, and potbound (requiring root manipulation) potted plants may require extra attention, plenty of water, and possibly some artificial shade to survive if planted in the hotter periods of the year. A few types of trees, especially some with large fleshy roots, often do not do well when planted in fall; the compromised (from transplanting) root system of these special cases should not be left to rot in cold wet soil.
B. In colder climate zones (about zones 4 or 5 and lower) where the ground freezes deeply, winter planting is not advisable. This is especially the case with evergreens. Hardy deciduous and most hardy evergreen trees may be planted in early to mid fall or in spring. If the tree or shrub is planted too late and the ground becomes frozen before the plant has a chance to establish a good root system, it may not be able to get enough water to avoid dehydration. Moisture intake by roots in frozen ground is limited or prevented. If more water evaporates from leaf surfaces, or even from the woody parts of the plant, than the roots can provide, the plant will suffer and may die. Frost heave is another possible concern with plants whose root systems aren't established before winter. Just as in warmer zones, summer planting should be avoided.
2. Check the site.
Be sure that you have enough room for the expected mature size of your tree or shrub. Remember that sizes on nursery tags do not typically reflect ultimate size, but average size after a certain period of time (for example 10 years). Trees and shrubs don't stop growing after that time period. Also check for proper drainage, compacted soil, necessary light level, and desired amount of protection from wind. Drainage can be tested by digging a small hole about a foot deep and filling the hole with water. If the water drains out within a few hours, drainage is good. If there is any chance that utilities are located near where you plan to plant your tree or shrub, call 811, or the appropriate "Call Before You Dig" number for your area, to have the location of any underground utilities marked. Avoid planting a taller growing tree or shrub in a location that could allow it to interfere with overhead power or communications lines. Any plant in a utility easement is subject to damage or removal by the utility company or authority. It is heartbreaking to have the utility company come by and ruin the look of a favorite tree a few years after it's planted.
3. Examine the root system.
A. If a potted tree or shrub is being planted, remove the rootball from the pot and examine the root system to check that the roots aren't potbound. If there are encircling roots, these must be teased out of the rootball or cut so that they do not cause a girdling situation later in the life of the tree or shrub. Teasing the roots out of the congestion is preferred and helps minimize transplant shock by avoiding unnecessary root damage. If the root system is too congested to make teasing the roots out practical, the rootball can be cut/slit down the sides and across the bottom of the rootball to sever the encircling roots so that they won't girdle the trunk or the root system in the future as the roots grow. These cuts are best made with a sharp knife or blade rather than tearing the rootball apart and further damaging roots. Quartering the rootball with these cuts should be enough to eliminate problems from encircling roots present at the surface of the rootball. If the plant has been previously repotted, it's possible that encircling roots are covered by the outer layer of soil added to fill the new pot. If this is suspected, the soil from the rootball should be removed and the rootball should be examined for signs of potentially girdling roots caused by poor potting techniques. Some gardeners prefer to remove/wash away all the original soil from potted trees and shrubs and plant them as bare root plants. This allows more complete access to locate and address hidden root system problems and eliminates the interface between the different soil types of the soil in the rootball and the native soil. Don't forget to carefully examine the rootball to ensure that the root flare (the location on the trunk where the top of the first root departs from the trunk) is not covered with excessive dirt. Occasionally, the root system of trees and shrubs is planted too deeply at the nursery. If there is excess soil above the root flare, this should be removed before planting.
B. If a bare-root tree or shrub is being planted, examine the root system for possible damage. Remove any damaged root structure. The roots can be soaked for a few hours to ensure that they are properly hydrated before planting.
C. If a balled-and-burlaped tree or shrub is being planted, any wire, nails, and staples should be removed and the burlap should also be completely removed if possible. Synthetic burlap, treated burlap, and even natural burlap can form a root growth barrier. Burlap removal may be done before the plant is placed into the hole with smaller trees or shrubs with stable rootballs. Larger trees and shrubs or plants with fragile or loose-soil rootballs may require the burlap to be left on the rootball until the plant is placed into the planting hole. If the rootball is too heavy for the burlap to be removed from the bottom of the ball after the plant is placed in the planting hole, as much burlap as possible should be removed from the sides. In no case should the burlap be allowed to be present near the exposed soil surface. Exposed burlap can wick moisture out of the rootball and cause excessive rootball dehydration. Examine the root system to ensure that the root flare is located at the top of the rootball. If not, the excess soil should be removed.
4. Dig the planting hole.
Dig a shallow bowl-shaped hole slightly more shallow than the height of the rootball (from the bottom of the rootball to the root flare). The root flare of your tree or shrub should lie just above the surrounding grade after planting is complete. Don't leave loose soil in the bottom of the planting hole. If the hole is accidentally dug too deep, fill the bottom of the hole and use your foot to firm the soil before moving the plant into the hole. Leaving loose soil below the rootball can negatively impact drainage and lead to rootball settling. The diameter of the top of the planting hole should be at least twice the diameter of the rootball. Wider holes are even better, especially in harder more compact soil. If planting a bare root tree or shrub, a cone of soil can be left at the bottom of the planting hole on which to place the root system. When planting in clay or wet soils, roughen the edges of the planting hole with the tip or edge of your spade to reduce the interface/boundary often formed by compacted/glazed soil resulting from the digging tools pressing against the sides of the hole.
5. Place the tree or shrub into the planting hole.
Be sure that the rootflare is not located below the surrounding surface grade/level. If drainage is an issue, the rootflare should be above the surrounding soil. Any loose roots should be properly placed and directed away from the trunk. Potentially girdling root problems must be addressed before going further.
6. Straighten the tree or shrub in the hole.
View the planting site from different directions to confirm that the trunk is vertical.
7. Fill the hole with native soil.
Generally, soil amendments are not advisable, and only the soil that was removed from the planting hole should be used to fill in the hole. A uniform soil texture throughout the entire potential rootzone aids drainage and helps to ensure proper root development. Organic matter should be limited to 5% of soil volume, even if the entire expected rootzone of the tree is amended or the tree is planted in non-native soil in situations like raised beds or berms. Before adding water, use your foot to firm the soil as the hole is filled with soil. Air pockets should be avoided. The soil can be watered in as the hole is backfilled if water is readily available on location. A shallow moat can be formed with excess soil to help provide enough water while the root system becomes established.
8. Mulch the planting site.
Mulch should be added at least as far out as the diameter of the planting hole. Wider mulched areas are beneficial. Proper mulch depth will vary with mulch type, but, if using pine bark or shredded wood mulch, 2" to 4" is generally sufficient. Mulching too deep can create surface drainage problems and deprive roots of oxygen. Remember to mulch wide, not deep. The area immediately adjacent to the trunk of the tree or shrub should be unmulched. Leave a couple of inches adjacent to the trunk bare to avoid fungal, disease, and pest problems. Excess moisture held against the bark on the lower portion of the trunk can encourage rot. Mulch placed against the bark can harbor disease and provide cover for gnawing rodents. In no case should "mulch volcanoes" be built around the trunk. Some gardeners make use of six to eight layers of newspaper or even cardboard under their mulch to reduce initial weed growth up through the mulch. Plastic, landscape fabric, and woven weed barriers should be avoided! These only cause major problems later on as seeds grow roots down though these materials and anchor themselves into the barriers. Removal can be problematic.
9. Water the tree or shrub in well.
It is important to ensure that the plant's roots are sufficiently moistened and that large air pockets are removed. Initial watering can be critical for the survival of the tree or shrub.
10. Use stakes only if necessary.
In most situations staking newly planted trees and shrubs is not necessary and can be disadvantageous. Unstaked trees generally develop stronger trunks and better root systems. If staking is required to ensure the stability of the plant's root system while it is becoming established, be sure proper techniques are used and that the stakes are removed as soon as the root system becomes established. This can usually be done during the winter following planting (after the first growing season). Stakes should be placed so that damage to the tree in high wind situations is avoided. Flexible ties allow some trunk movement to encourage more natural trunk and root growth.
11. Prune only as necessary.
Remove any dead, damaged, or rubbing branches at planting time, but don't prune any more than necessary. The outdated technique of trying to match top growth with root mass has been well proven to be detrimental to the rapid establishment of the tree or shrub. Removal of top growth actually slows root development, increases stress on the plant, and increases the time it takes the plant to become established.
12. Provide proper after-care.
It is important to properly water your tree or shrub, when needed, until the root system is well established. A finger can be inserted 2" to 3" into the ground to test for proper moisture levels. Soil at the level of the rootball should be kept moist but not wet. The soil's surface should be allowed to begin drying in between waterings. Initially, watering may have to be done every few days or at least once a week, depending on local conditions, during drier weather, but after the first few weeks, watering should be done less frequently. Longer (deeper), less frequent watering is much better than shorter (quick), frequent watering. Check the soil around and inside the rootball to ensure proper moisture levels. If rootball or backfill soil texture and/or structure is significantly different than the planting site's native soil, improper drainage can be an issue. In such cases, it is possible for the rootball to remain soggy while the surrounding soil dries out or for the rootball to dry out while the surrounding soil maintains adequate moisture.