An Olympian effort: what comes down must go up.
If no established trees exist on the site, the contractor is required to plant trees totaling a minimum number of caliper-inches. The city itself is planting about 700 trees per year, most of them 2-1/2 to 3 in. in diameter.
The new generation of trees will improve esthetics, lower temperatures by keeping the sun off paved surfaces, provide shade and comfort for Olympic visitors, disrupt wind tunnels between downtown buildings, and stabilize the water table by retaining rain.
Lowery and other officials have developed guidelines for the ongoing planting and maintenance. Lowery works with and helps lead the Georgia Tree Coalition, a group that coordinates donations, plantings, and education programs in the private and public sectors.
Many people suggested planting magnolias because of their traditional association with the South. But, Lowery notes, magnolias were not recommended because they are hard to transplant; large numbers of birds roost in them, causing serious health problems; and they drop a lot of leaves, which tend to block catch basins because they do not degrade quickly. Likewise, the Bradford pear tree not long ago was considered an urban supertree, but professional horticulturists and landscapers are discovering that they fall apart in wind-storms after 12 to 14 years, Lowery says. City planners now are shying away from them.
Early on, willow oaks were recommended for Olympic plantings because they are hardy, drought tolerant, and easily transplanted. However, Lowery was concerned because contractors were planting so many that they. were approaching a monoculture. He worried that disease could spread rapidly through the trees and wipe them out, much as Dutch elm disease did in many cities years ago.
Crape myrtles were later used a great deal. Certain varieties are insect-resistant and heat-tolerant, and city officials note that some species will bloom during the Games. There are many existing crape myrtles on private property, but residents tend to crop the tops, mistakenly believing the cutting will promote blooming. "All it really does is give us a lot of stubby, flat-topped, seriously-shocked crape myrtles," Lowery says.
Another recommended species is the European hornbeam, which is resistant to insect and disease problems. The tree is slow-growing but strong. Bald cypress also is favored because it thrives under tough urban conditions and has very hard wood.
Lowery takes an uncomplicated approach to planting trees: dig a hole a bit wider but no deeper than the root ball, then put in the tree, fill the hole, and mulch the surface. He stresses that the wire basket, straps, ropes, and burlap often found on the root ball should be removed. Many people believe the basket will have no effect on the tree, but Lowery disagrees. "It might not kill the tree, but it will knock down its vigor as it interferes with normal root growth," he says. "In urban conditions, anything that detracts from a plant's vigor opens the door to disease and insect problems."
And Lowery avoids using root barriers, which are gaining popularity as a way to prevent tree roots from disrupting adjacent sidewalks and utility lines. In theory, the roots grow down and under the synthetic barriers, which are installed like underground walls. But Lowery believes downward growth is stopped by compacted soil and a lack of water and air. This could create a "flower pot" effect for the roots, he says, and a less stable tree.
Due to budget constraints, there is no fertilization or insect control program in place. However, starting the year after planting, the beds beneath young trees are treated with herbicides, then mulched, to eliminate competition from vegetation such as Bermudagrass. A spray mix of Roundup[R] (Monsanto Company, St. Louis, Missouri) for emerged plants and a pre-emergent herbicide, is used successfully around newly planted trees.
"We like this approach," Lowery says, "because it keeps our lawn mowers from getting too close and knocking down or damaging the new trees. And it keeps the weeds and grass down for a whole growing season. We use the same program under our more mature trees because it keeps the tractors and mowers off the root systems, which are pretty shallow or right on the surface because we have high soil compaction and so much granite in the soil in many places."
Three to four times as much trimming as usual was done in preparation for the Games. Branches that appeared weak and in danger of falling were removed. So were limbs that would get in the way of spectators and TV camera angles, Lowery says. And some cutting was done to give security personnel a clear view of the proceedings and to eliminate potential hiding places for troublemakers.
Games organizers had asked the city to improve camera coverage of cross-country and bicycle races by removing many street-side limbs of mature trees along the race routes. City officials said no; they wanted to preserve the canopy and anticipated opposition from nearby residents. They also were concerned about liability, because all the weight of the limbs would be on one side of the trees, making them unstable.
Ninety percent of the city tree planting was done by volunteers or jail inmates in community service programs. The city's tree maintenance workload will increase in five years, when, by law, trees planted by contractors on public rights-of-way will become the responsibility of the city. Lowery is recruiting volunteers through the Master Gardener program run by the local University Extension Service to help with street tree trimming and pruning.
Atlanta will benefit from the current work generations after the Olympics are over, Lowery says. "To maintain a canopy, it's good to have trees in various stages of development so they aren't all getting old at the same time, and to maintain the integrity of the city's bio-infrastructure. We're putting together a good mix right now."
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|Title Annotation:||tree management in Atlanta|
|Date:||Aug 1, 1996|
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