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Monday, Oct 23, 2017
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As summer heats up, big trees are made in the shade

Last week I was reminded of how wonderful a shade tree can be. I was outside my daughter and son-in-law's Temple Terrace home around noon, standing in the full sun to hand-water some new foundation plants. Of course, it didn't take long before I was hot and wet with perspiration. I persevered a bit longer (as all dedicated gardeners do), but before moving on to my next task I took a break and sat for awhile under the generous canopy of a mature laurel oak. Whew, what a difference a few feet can make! The air next to the massive trunk was 10 degrees cooler than the air directly exposed to the harsh rays of the sun on this day in early June. I cooled down quickly, a gentle breeze helping to evaporate my sweat. I was in a great spot to appreciate my gardening handiwork and take in the natural sights, sounds and smells of a quiet old suburban neighborhood.
Mature shade trees are giant air conditioners. They not only help remove dust and other pollutants from the air, they cool it by dissipating heat from the surfaces of their leaves, a process called transpiration. Evaporative cooling takes place as a result of transpiration - as it also does when we perspire. So, by stepping under the big oak, I'm, in a manner of speaking, letting the tree do some of my sweating for me! Unfortunately, many new neighborhoods in our area don't have any mature shade trees. They are on former pastureland or citrus groves. Hopefully, the developers of these neighborhoods have established trees that will someday provide homeowners and their kids a pleasant respite on a sunny summer day. If they haven't and you live in one of these neighborhoods, or for whatever reason you have a shade tree-less yard, plant some yourself. There are plenty of beautiful Florida-friendly species from which to choose. Be sure to consider the tree's mature height when you plant and pick a spot where it can safely grow up. For more trees - and shrubs, vines and more - check out the handy Florida-friendly Plants Database at floridayards.org/fyplants/index.php. Winged elm (Ulmus alata) Mature height: 45 to 70 feet; Spread: 30 to 40 feet; Resistance to wind damage: medium to high; Growth rate: fast. Chinese elm (Ulmus parviflora) Mature height: 40 to 50 feet; Spread: 35 to 50 feet; Resistance to wind damage: low; Growth rate: medium. Sycamore (Platanus occidentalis) Mature height: 75 to 90 feet; Spread: 50 to 70 feet; Resistance to wind damage: medium to low; Growth rate: fast. Laurel oak (Quercus laurifolia) Mature height: 60 to 70 feet; Spread: 35 to 45 feet; Resistance to wind damage: low; Growth rate: fast. Live oak (Quercus virginiana) Mature height: 40 to 80 feet; Spread: 60 to 120 feet; Resistance to wind damage: high; Growth rate: medium. (Note: Laurel oaks have an average life span of only 40 to 50 years and can become a hazard when they begin to die. Because of their large size, removal costs are high.)

Craig Chandler is a professor emeritus of horticultural sciences at the University of Florida's Gulf Coast Research and Education Center in southern Hillsborough County.

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