By: Brenda Bolton, Mobile County Master Gardener
Almost one year ago, I finally road-tripped the American West. I ventured into beautiful national parks, rounding one bend to the calm gaze of a huge grey wolf. I watched in awe as a lone buffalo lumbered to our car, passing my open window so close I heard his snort. I could have reached out to rub his massive head, count the burrs in his curled mane, and watch the raw power of muscle and bone.
I brought home with me a souvenir, a photograph of that buffalo, and the unexpected gift of this epiphany: I was meant to live here, on soft, green grass under a canopy of trees in coastal rains.
The West’s moonscape drama of dust and rock and night sky, though starkly beautiful, cannot, for me, replace the simple shift of air under a live oak just before an August rain.
At the height of hurricane season, when I walk my dog, I stay in the shadows of street oaks. There are places where their old limbs swoop low, as though to offer a lift up into their embrace. I pass sunny parking lots where cars cluster like ants into any shade. Understandable, since shade reduces ambient temperatures by 10 degrees and surfaces 20-45 degrees, according to USDA urban “heat island” studies. That translates into reduced energy costs. A 2010 USDA Forest Service study (Peper, et al) claims tree shade saved Orlando citizens half a million dollars annually in air conditioning costs, and “. . . the live oak . . . accounted for 42 percent of the energy benefits although it represented only 25 percent of the [tree] population.”
The USDA lists the live oak with 80% or higher hurricane survival rates, its highest rating. In August storms, those dark, gnarled limbs, furred with resurrection fern, groan and lumber against the wind and rain like that Western buffalo’s slow, heavy, purposeful motion, head resolutely down, burly black shoulders rippling with strength.
Out West, there are hundreds of miles with no shade and no wind break. Without trees, landowners build staggered lines of oddly shaped wooden wind breaks, like disfigured fencing, to control the shift of earth. The Western sunlight, lacking coastal cloud cover and tree shade, actually stings the skin. Here, according to a 2002 study by Grant, et al, 90% oak shade can provide up to a count of 30 UV protection against skin cancer. Therefore, USDA recommends trees on playgrounds since future skin cancers develop from youthful overexposures.
In August rains, tree crowns collect, hold, then evaporate intercepted rainfall, (Peper, 2010), keeping it from ground level run off, and oak roots drink more than any of us think about. But we should. We should measure every drop. And the experts have. In an EPA study in Charlotte, N.C., the street trees there were found to absorb 209.5 million gallons of storm water annually. In Orlando, Florida, the municipal forest reduced runoff by 284 million gallons annually, (Peper, 2009b), valued at $851,291.
Live oaks are the work horses of our Southern ecosystem, reducing a vast range of the ills of modern life: excessive heat, carbon dioxide, emissions, noise/air/water pollution, UV rays, storm water runoff, erosion, compacted city soils, street flooding—while improving respiratory, skin, and even mental health, enriching soils, increasing property and commercial values, feeding and sheltering birds and butterflies, and sheltering us from winter wind and harsh August sun.
In “cost vs benefit” reports of large trees, all I’ve read comes down on the side of a net gain. Those roots that raise your sidewalk? They also burrow, aerating compacted soils so that floodwaters are better absorbed. Those leaves that shed in spring reduce erosion, aerate, and enrich soils. Experts place a net gain dollar valueon a large tree of $149 annually, almost $5,000 over a lifetime (Peper, 2010). Imagine the value of a 200-year-old oak.
We don’t appreciate the gifts of our oaks. Like that big, powerful buffalo, the oaks were here first. We invaded their territory with our concrete, underground pipes, and overhead wires. Instead of seeking ways to save them, we shortsightedly sacrifice a healthy tree with a lifespan of several hundred years to make a place for this year’s trendy fast food spot, predestined to close on their corporate ten-year business model schedule.
So plant a live oak (Quercus virginiana), or its smaller twin, the sand live oak (Quercus geminata), but don’t plant it beside your back door, under power lines, or over your sewer lines. Call before you dig. With a mature average canopy of 60-80 ft, give a wide berth so it can mature into the beauty it’s meant to be. Check into underground growth cell systems that encourage the oak’s shallow roots to stay underground. Consider a meandering walkway around trees or bridge over raised roots. Use pliable, permeable surfacing over root zones. Mulch under their shade canopy, then enjoy a container shade garden there. For Alabama Extension planting advice: https://www.aces.edu/blog/topics/landscaping/tree-selection-planting-care/
One mature live oak produces enough oxygen for up to four people daily. The text of a recent poster, author unknown, makes my point:
“If trees carried free WIFI, we would plant them in every bare spot on every street in America and never cut one down. Too bad all they do is make the very oxygen we breathe.”