The list of benefits that trees provide is so long you might believe it's exaggerated. But it's not. Reduced pollution, erosion control, wildlife habitat, energy saving, and enhanced human comfort and well-being are all documented, long-term consequences of tree planting. But too often the focus is on the quantity of trees to plant rather than their individual quality and proper planting. It is important to know you are planting the right tree in the right place the right way. These are the issues that determine an individual tree's health and longevity, and so are the subjects of this article.
Choose a Tree Adapted to Your Site
Use all available resources to make a list of trees adapted to your area. Many books with general information about tree adaptation are available at libraries. Also, check with your cooperative extension agent, master gardener, or parks department for a list of locally adapted trees. Factors to consider include tree size as well as shape and growth rate; whether it is deciduous or evergreen; climate adaptation; soil and water requirements; pest problems; and the amount of litter produced. Naturally, a tree's ornamental characteristics -- flowers, fall color, foliage texture, and other features are also important.
Once you have a list of candidates, check it with advisors at local nurseries. Your list will narrow quickly, and you can use factors such as flowers, flowering time, or fall color to make the final selection. Finally, locate in your area a mature tree of the species you think you want and ask the owners what their opinions are about it.
If the tree you choose is not readily available, don't hesitate to place a special order for it, or to order it from a mail-order supplier. It is more important to get a healthy specimen of the right tree than to plant right away.
Choose a Healthy Tree
It pays to be a smart shopper when buying trees. As hard as most nurseries and garden centers try to properly care for their trees, the longer a tree has been in the nursery, the greater the chance for something to go wrong. A missed watering here, not enough fertilizer there, and a tree will suffer. Such trees are likely to grow slowly or poorly once they're planted in the landscape.
Trees are sold three ways: bare-root, balled & burlapped (B&B), and in containers. What these trees look like and brief descriptions of the advantages and disadvantages of each is shown and explained below.
Examine a tree carefully before buying. The largest individuals of a group may be too large for their root-balls. The smallest trees of a group may be stunted from some type of stress. In general, select a tree of modest proportions. Look for a tree with a balanced canopy and evenly spaced branches extending out in all directions. It is best if branches are distributed along the entire length of the trunk.
The trunks of some trees have been headed, which causes several branches to grow from just below the cut. Such a tree may appear attractive and in good proportion, but for large-growing trees, the branches may be too low and weakly attached unless most are pruned out.
Foliage growth along the lower trunk contributes to its strength. The trunk should be straight and evenly tapered from top to bottom. Ideally, the tree should be able to stand up by itself without staking. If not, it will require staking for a longer time after planting.
Avoid trees with broken branches, wounds on the trunk, poorly colored foliage, obvious signs of insects or disease, or a previous season's growth of less than six inches.
If you can't plant as soon as you get your trees home, make sure you take care of them until you can. Temporarily store all types of young trees in a shady location. Partially bury the roots of bare-root trees by digging a shallow trench, placing the roots in the trench, and covering them with moist soil or organic matter. Take care to ensure that the root-balls of B&B and container trees don't dry out.
Especially if you suspect drainage problems, dig a test hole near the tree's site a few days or weeks before planting. Fill the hole with water, let it drain, then fill it again. Time how quickly the water drains. If it is less than 1-inch per hour, or if it hasn't drained completely in 24 hours, you have a drainage problem. Solutions include planting elsewhere, planting in raised beds or mounds, or installing a drainage system (consult a landscape contractor). You may be able to improve the drainage by drilling through the hardpan in the bottom of the hole. Ask your county cooperative extension office or nursery to find out about local soil conditions and probable depth and thickness of the hardpan.
How to Plant Bare-root Trees: Set bare-root trees atop a small mound of soil in the center of the planting hole, and spread the roots down and away without unduly bending them. Identify original planting depth by finding color change from dark to light as you move down the trunk towards the roots. If the tree is grafted, position the inside of the curve of the graft union away from the afternoon sun.
How to Plant B&B Trees: Handle the root-ball carefully so it doesn't break or crack. Lift the soil ball and position it in the center hole. Gently tamp to remove air pockets as you fill. Once stabilized with backfill, remove burlap. Continue backfilling and watering to settle the soil. Don't cover the top of the root-ball with backfill because it could prevent water from entering.
How to Plant Container Trees: Lift the plant out of container prior to setting the root-ball in the hole. Eliminate circling roots by laying the root-ball on its side and cutting through the roots with shears. Don't cover the top of the root-ball with backfill because it could prevent water from entering.
Water After Planting
Create a watering basin at least 4 to 6 inches high just outside the root-ball. Fill it with water, let it drain, and repeat. Recheck the planting depth. If the tree has settled below the surrounding soil level, it should be raised. For bare-root trees, gently pull up on the lower trunk. For container or balled & burlapped trees, carefully push a shovel under the root-ball and pry it upward while lifting up on the lower trunk. In each case, moist soil will settle under the roots and raise the planting depth.
Stake, if Necessary, and Mulch
A tree with a strong trunk stands on its own without staking. However, if the tree was staked in the nursery or if you are planting in a windy location, proper staking will support the tree during its first years in the ground. Drive in two stakes, one on each side of the tree and just outside the root-ball. Position the stakes so that a line drawn between them is perpendicular to the strongest prevailing wind when the tree is in leaf. Tie the tree to the stakes with wide flexible ties. Determine how high to attach the ties by running your hand up the trunk from the base. The minimum height at which the top of the tree remains upright is where to secure the ties. Use wide ties to reduce damage to the trunk, and don't tie the tree too tight. A tree that can sway somewhat in the wind will develop a stronger trunk.
Apply 3 to 4 inches of organic mulch around the base of the tree to conserve moisture and reduce weeds. Keep it at least 6 inches away from the trunk.
Watering. Bare-root trees do not need to be watered again until two to four weeks after growth resumes. Container and B&B trees need regular watering until their roots grow into surrounding soil. During hot weather, these trees may need to be watered every two to three days to keep the root-ball moist. Occasionally wetting the soil outside the basin will ensure that roots develop into the surrounding soil. Expand the basin as the tree grows.
Pruning. Most new trees need no pruning the first season other than to remove broken branches. Pruning may reduce the total growth of a young tree. These cautions noted, if large, vigorously growing branches are too low or competitive with more desirably placed branches, you can safely cut them back. This preserves some foliage but reduces competition. Eventually they can be removed.
Pinch out the tips of vigorous growth in order to stimulate side branching. If the leader is growing vigorously and no laterals are forming at a height you would like, pinch out an inch of the tip growth when it is at the height where you would like a permanent branch. Several shoots will grow from below the pinch. When the new shoots are 3 to 4 inches long, select the most vigorous (hopefully the top one) for the leader and pinch back the other shoots. If growth is vigorous, this can be repeated a couple of more times, allowing two or three main branches to be selected the first growing season.
Fertilizer. If young trees are growing slowl poorly colored foliage, they may benefit from adding a nitrogen fertilizer to the watering basin. Remove support stakes soon after the tree can stand on its own.
Lance Walheim is a citrus farmer and garden specialist living in Exeter, California
Photography by National Arbor day Foundation