AB-Trick Or Tree?: Installation Tips - FOCUS: Tree Care

Trees have a reputation.

In the eyes of those who admire the dancing leaves on their branches or rest beneath their shade, trees bear a cathedral-like stature and endurance.

But despite their reputation, there is one moment when trees are the underdog and can be defeated: during establishment. "Planting is one of the most important cultural practices that determines the success or failure of trees," explained Davis Sydnor, professor of horticulture, The Ohio State University, Columbus, Ohio. "To get the most satisfactory performance from trees, attention should be given to planting details."

Trees must be planted at the right depth and receive the correct amount of water to flourish. Planting too deeply, using excessive mulch and forgetting to check for adequate soil drainage are just a few of the common establishment errors that can be detrimental to a tree’s future health, causing decay, promoting root rot and fungus, and weakening or even killing the tree. And, often, no amount of proper maintenance can correct a faulty planting job.

"Using quality plants and following good cultural practices, such as watering, pruning and fertilizing, will not compensate for poor planting techniques or poor plant selection," Sydnor confirmed. "As the emphasis on and need for urban plantings increases, so does the need for a better understanding of the stresses trees encounter."

PLANTING SEASON. After selecting a healthy tree (see sidebar below) and working with the client to choose a proper location for that tree, a contractor can determine an adequate planting time.

In Southern California, Ron Matranga, residential division manager, Atlas Environmental Services, Spring Valley, Calif., said the key to proper timing is to consider tree type, regional weather conditions and the tree’s possible reactions to that area’s specific climate.

Typically, the best time for tree planting is in the fall after temperatures have cooled down and before the soil freezes. "Spring growth is stressful – the tree uses a lot of energy to put out leaves and tissue," Matranga said. "Planting in fall allows the tree a chance to acclimate to the site before the rush of spring growth hits."

Fall also is a particularly favorable planting time in southern states. For instance, hot, dry summers in Austin, Texas, force Scott Harris, urban orchard coordinator, TreeFolks, to plant trees from November until March so they can get established before temperatures increase. "Trees have a much higher survival rate when they are planted during the dormant season," he said, adding that these cooler months also are easier on his employees.

Tree species also dictate whether spring or fall is more suitable for planting, added Kevin Peters, district manager for the Alpine division of the Care of Trees, New England area. For instance, birch and maple trees have a better chance of recovery when planted in the spring, while many evergreens are hardy and can be planted in the fall, Peters offered.

THE DIRT. Contractors’ opinions vary on the value of soil amendments. "Many contractors feel that soil should be amended and others feel they should use the existing soil conditions so the tree learns to grow into that environment," Peters explained.

Matranga suggested contractors use existing soil unless 50 percent or more of it is in poor condition for planting, such as on a construction site where much of the high-quality loam or topsoil has been removed or compacted by heavy machinery. "If you create a different soil condition in the hole, the tree roots will refuse to penetrate the native soil and establish themselves," he said.

Even more important than soil amendment is soil excavation. Digging the correct hole size is a crucial and commonly flawed tree planting step.

With balled-and-burlapped or container trees, measure the height and diameter of the rootball, Sydnor said. The hole should be two to three inches shallower than the rootball or container and 2 to 3 times as wide, Matranga suggested, pointing out that if the hole is too deep, the tree will settle further into the soil and the root flare won’t receive the oxygen it needs, increasing the amount of water building up around the tree base and making the tree more prone to root rot.

"Planting the tree too deep will cause soil to hold moisture against the bark, thus softening it and presenting an opportunity for insects and diseases to enter," Harris added, using a swimming analogy to explain why trees should not be planted too low. "Everybody loves to swim, but it’s very important that certain points on your body are allowed to come up above the surface."

The planting hole is wider than it is deep so tree roots have loose, penetrable material to grow into horizontally, which is vital for the tree to establish itself in its new environment, Matranga specified.

Though high planting is less severe than low planting, it should still be avoided, said David Chinery, Cornell Cooperative Extension of Westchester County, N.Y. "Plants are often planted high because the area is a wet site, the soil is of poor quality or the contractor wants the plant to appear bigger and taller," he indicated. "An unmulched, uncovered, high rootball will dry out quickly and lead to drought stress."

ROOT DOWN. Ready-to-plant trees come in three forms: bare-root, container and balled-and-burlapped. Each tree style requires several specific considerations.

In Southern California, Matranga said he only uses container trees. A contractor should never lift a container tree by the trunk, Matranga stressed. Instead, a 15-gallon container, for example, should be laid on its side so a contractor can hit it softly with a hammer to free the rootball.

Because container trees tend to have slight circling or girdling roots, scoring the rootball sides at three or four points around the ball with a sharp knife is important. "Studies on girdled and container-bound roots show that roots will continue circling because they were grown to do that," he explained, pointing out that scoring should be done with a sharp instrument in swift, vertical motions as not to rip or tear the roots. "Cutting the circling roots prevents them from strangling the tree to death later on."

Since container tree roots are protected, they are less vulnerable to damage during transport. But contractors should keep bare-root and balled-and-burlapped trees’ exposed roots moist prior to planting. These trees can dry out quickly if they are sitting in a storage yard and are not watered frequently.

For balled-and-burlapped tree planting success, rest the rootball in the hole’s center and reshape the soil at the bottom so the tree stands straight, Harris instructed. "After adjusting the tree, pull the burlap and any other material away from the sides and top of the rootball," he continued. "Don’t try to get the burlap material out of the hole – just let it rest beneath the rootball. Exposing the sides of the rootball to the soil will enable the tree’s roots to grow in the most important directions. Also, do not adjust or lift the tree after its ball has been unwrapped, or the rootball can be damaged."

To avoid tree strangulation, remove any twine or wire used to tie the burlap around the rootball or trunk of the plant, Chinery said. "Twine rotting should not be relied upon to prevent constriction," he warned. "A surprisingly large number of trees are killed in this way."

Bare-root trees require a slightly different planting technique than container or balled-and-burlapped trees. A wide hole is still necessary, but soil should be mounded up at the bottom of the hole and the tree roots should be laid across that mound, Peters explained. "This typically is a less expensive process," he said, pointing out that a tree requires one year of recovery after planting for every 1-inch caliper of its size. "Bare-root trees are often younger as well, so their chance of survivability is higher. For instance, a 6-inch caliper tree will go through six years of transplant shock. The younger the tree, the shorter its recovery time."

Holes for all three tree forms should be backfilled with the site’s original soil, Harris said, pointing out that the best soil for root growth has space for both air and water. "To backfill correctly, fill the hole until it is half full, flood the hole with a slow hose and then tamp it gently with your foot to firm the soil," he described. "Repeat this until the hole is full. This method will remove any large air pockets in the soil that can cause problems later on."

After adding the rest of the soil, build a small ridge of soil around the planting hole to act as a water well, Chinery advised.

LIFE AT STAKE. While staking newly planted trees is common, it can be unnecessary depending on the species, size and location of the tree, Sydnor pointed out. "Small trees up to 2 inches in diameter rarely require staking, while larger plants may or may not require staking," he said. "In research measuring the effect of rigid supports on staked trees, unstaked trees were found to have greater trunk diameter than their staked counterparts. Unstaked trees also were lower in overall height while having bigger root systems and had greater trunk taper, meaning that the trunk increased in diameter more rapidly."

Harris typically won’t stake trees unless he plants them in an area with excessive wind or traffic. Both Harris and Peters agreed that if they do stake trees, they do so only for the tree’s first growing season.

On the other hand, because nursery-grown trees tend to lack trunk strength, Matranga believes staking matters. He will keep stakes on a maximum of three years, depending on the tree’s stability, species and location. "If someone walks on crutches all his life, his legs won’t know what to do," he explained. "If staking is done properly, a tree should stand on its own after 12 to 18 months."

Typically, two stakes and one set of ties should be used as low as possible, while still supporting the top of the tree, Matranga described. Rubber tree ties are better than hoses, wires, ropes or other materials that can bite or cut into the tree, he pointed out.

The ties should fit securely around the tree, Sydnor added. "Increasingly, people are trying to provide for flexibility and movement at the tying point, not realizing that this increases the risk of mechanical injury," he pointed out.

Guying, another form of staking or supporting a tree, is done with guy wires and normally is used with trees more than 4 inches in diameter, Sydnor said. "They (guy wires) should be attached at or above the lowest branches and then affixed to stakes driven 18 inches into undisturbed soil," he indicated. "For trees more than 5 inches in diameter, guy wires should be anchored with earth anchors or deadmen."

Sydnor recommended removing guy wires after one growing season to prevent girdling.

AFTER SHOCK. Trees have immediate needs after planting to help ease the shock of being thrust into a new environment.

For at least one to two years after planting, trees should receive about 1 inch of water per week during growing seasons, Sydnor stressed, pointing out that too much water also can be a problem. "Excessive water probably kills more plants than water deficiency," he said. "To help determine when watering is needed, plant a drought indicator plant in the rootball of the tree. Indicator plants, such as impatiens, coleus and ajuga, wilt dramatically. The tree can be watered whenever the indicator plant has been in shade for at least one hour and is still wilted."

In addition to infrequent and deep irrigation, mulch should be immediately applied to the soil surrounding a freshly planted tree to help retain moisture, enhance soil nutrients, prevent weeds and protect the tree from mower damage.

Excessive mulching, or what Peters called "volcano mulching," can promote a wet environment for fungus and root decay, so he recommended spreading a 2- to 4-inch depth of natural wood-chip generated mulch sprinkled out 1 to 2 feet from the tree.

"A lot of people use pine bark or cedar mulch, but it doesn’t decompose as quickly or have the organic matter qualities that natural wood chip mulch has," Peters pointed out. "Often times we’ll use wood chip mulch and then apply a small amount of cedar mulch on top of that for the ‘look’ clients want but the benefits the tree needs."