Tree myths: So much of what you've been told is wrong

By Joel M. Lerner
Saturday, February 6, 2010; E04

Many planting practices that were thought critical to the health of trees are simply myths. Some ideas that have long been accepted by experts have proven to be incorrect. This is understandable because it can take generations to comprehend the sophisticated systems of these magnificent plants. While you're enjoying the warm and cozy indoors this winter, let's examine some tree myths.

Myth 1: Newly planted trees need to be staked or guy-wired.

This is generally incorrect. Balled-and-burlapped and large-container trees are bottom-heavy, so they can stand on their own. Wiring them in place kills far more trees than it helps because in most cases the wires are never removed. As trees grow, living layers of tissue called cambium, just under the bark, grow around guy wires, interrupting the vital flow of nutrients that travel through the vascular system. Trees will ultimately die when guy wires cut off circulation.

It's not staking and using guy wires that kill trees, but the lack of stewardship. This is a common problem, especially for street trees that are planted in holes and never given care again. Without removing stakes within one year of planting, and without enough water, trees die. Some homeowners continue to believe that unless trees are staked into place, a tree hasn't been professionally installed. Yet the latest advice from arboriculturists and horticultural researchers is to plant trees in the ground properly, allowing them to bend in the wind, which will help them grow stronger. If a tree is a little crooked, you can easily straighten it the next growing season.

One exception to this rule is if you are planting a bare-root tree or one that is a poorly rooted plant from a container. In those situations, staking might be necessary. Drive stakes outside the root ball, using ties that can be fastened loosely around tree branches. Old hosiery is effective as tree ties. But no matter what you use, closely monitor trees to make sure they are not being cut into.

Myth 2: When planting a tree, dig the hole twice as wide and twice as deep as the root ball, installing it so the tree trunk is planted at ground level and making sure you have properly prepared the soil.

Install root balls about 25 percent higher than ground level. Place the tree or shrub, and then fill the hole with a mixture of one-third compost and two-thirds native soil. Pack the soil mixture firmly so that any air pockets are filled in. Water the tree well, making sure the soil stays moist, but not wet, while the plant establishes itself, or until the ground freezes, if you've planted in fall or winter.

Research indicates that newly planted trees do best on a solid platform of soil. Planting trees and shrubs too deeply is a common mistake that can lead to killing the plant. Avoid allowing the root collar (the flare just above the point where the roots join the main trunk) to be covered with soil or mulch. The roots need moisture, but the bark and root collar need air. If you cover them with soil, the bark will rot, causing the same girdling effect as wire. The plant won't die right away; it might decline over a period of years. If you have trees balled in burlap, be sure to remove any ties that are holding the burlap to the trunk. If ties are inadvertently left, they will girdle the tree and eventually kill it. I have seen this occur a number of times.

Myth 3: Newly planted trees should be "fed" regularly.

Trees don't eat. They absorb nutrients and can be fertilized in fall with a general-purpose dry fertilizer using a broadcast spreader over the surface of the root zone. Use a product with an analysis of about 10-6-4 (nitrogen-phosphorous-potash). Trees receive their nourishment through osmosis and need moisture to absorb these minerals through their cells. They require a balance of properly moist soil that has been prepared to allow enough air space for the roots to grow and absorb the minerals that the soil contains. Clay is loaded with minerals, and if it's mixed with enough organic matter, it will be easy for trees' roots to reach out and take what they need.

Container trees that come from nurseries are often planted in soilless potting mixes. Because there is no soil in the mix, there will be no soil nutrients released from the medium. You will want to pay special attention to these and be sure to use a general-purpose dry fertilizer for the first couple of years while they are establishing. Never put fertilizer into the planting hole when installing.

Test soil before planting. The pH, or acid-to-alkaline balance, needs to be correct. Some trees, such as hickories and oaks, like a more acidic soil. Others prefer "sweeter" soil. Have the soil tested through the local County Cooperative Extension Service in your area. The USDA's National Institute of Food and Agriculture,, has a listing of offices.

Myth 4: Trees need to be watered constantly.

Trees need to be watered when they need water -- not before or after. This is not rocket science. Stick your finger in the soil and if it's dry, water. If it's moist, don't. Most plants do not like to be over-watered, and can die from constant watering. Rain gauges, moisture meters or other soil-moisture indicators can make things more complicated. You should be careful if you have an irrigation system that runs on a regular schedule. These systems can be fine for lawns, but deadly for trees that don't like constant moisture. Ascertain the moisture requirements for trees you choose to plant or those you already have.

Myth 5: Drought-tolerant trees don't need to be watered.

Yes they do, especially when they are becoming established. Xeriscaping -- the practice of using native plants to minimize watering -- doesn't mean not watering. The key to any xeriscape or water-efficient landscape is proper water management. Drip irrigation and spray heads should be used where necessary. A couple of trees that tolerate dry soils are paperbark maple (Acer griseum) and lacebark elm (Ulmus parvifolia). During establishment of trees, during the first couple of seasons, they still must be watered, but only when necessary.

Finally, one requirement that is not a myth is the most critical guideline to keep in mind. Before you plant even one tree, know what's below it. Have your utility lines located by calling 811, the federally mandated "call before you dig" phone number.

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md.

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