Ask a Master Gardener: Preserve A Legacy: Mobile’s Tree Canopy

Government Street Oak Allee. Photo by Bill Boswell.

By: Brenda Bolton, Mobile County Master Gardener, www.mobilecountymastergardeners.org 

Close your eyes and imagine Mobile’s best days:  spring days wrapped in Southern sunshine, softened by cool bay breezes that are captured, lifted and carried inland on the tips of overstory trees, air made light by the play of leaves, summer days cooled by shade; winter’s windy, icy days assuaged by evergreen soldiers standing guard; or sleepy autumnal afternoons, when the drop and rustle of leaves make music, if only we will listen.

But today is high summer, and the only relief beyond the door is that shade tree in the yard.

In 1979, the Arbor Day Foundation named Mobile a “Tree City USA,” Alabama’s first.  We rhapsodize about the beauty of our trees and Government Street’s stunning oak allee, but we forget their practical value. They earn their keep:

·         One mature shade tree cools surrounding surfaces by 20-45 degrees. 

·         The earth’s trees remove about 1/3 of fossil fuel emissions annually, one mature tree reducing atmospheric carbon by 917 pounds.

·         A single mature tree can supply a day’s worth of oxygen for up to four humans.

·         A mature Live Oak will intercept and mitigate 8,161 gallons of stormwater runoff annually. (*Arbor Day Foundation statistics)

High summer means Hurricane Season, and a little quick research will tell you which trees are storm strong. Healthy Live Oaks (selected Urban Tree of the Year by the Society of Municipal Arborists in 2013) are known for their ability to withstand hurricane winds due to their deep, widespread roots that firmly anchor, their spiraled limbs and branches of strong dense wood that flex rather than snap, and even their leaves, which curl in a Fibonacci sequence form in wind, minimizing friction. Live Oaks compartmentalize after injury, slowing or stopping the spread of damage.

Visit: https://gardeningsolutions.ifas.ufl.edu/plants/trees-and-shrubs/trees/trees-that-can-withstand-hurricanes/  for a list of storm-strong trees.

While we agonize over a tree toppled by a storm, we often forget to notice all those that endured, blocking wind and guarding our homes.  It’s important to note that these benefits are those of mature trees, reminding us that a replanting program—while good—does not provide the same benefits as preserving healthy mature trees. But we are gardeners, and so we plant.  Or replant. A tree becomes a large, permanent structural element that, when properly planted, increases property values up to 19% (National Association of Realtors).  A tree is a lifelong companion, a playground for our children, the backdrop of our lives.

A good canopy tree becomes a family legacy. It deserves careful planning:  Plant in dormant season if you can, not high summer. Assess expectations: Do you want a year-round canopy?  Choose an evergreen (Live Oak-Quercus virginiana, Magnolia grandiflora, American Holly-Ilex opaca, all storm strong).  Do you want a landscape feature?  Choose a tree with arresting architecture (Live Oak), seasonal color, blooms, beautiful leaves, such as Red Maple (Acer rubrum), Magnolia, American Holly, or unique bark such as Sycamore (Platanus occidentalis) or River Birch (Betula nigra).  Select a healthy specimen with a single strong central leader and check that roots are not tightly girdled around the root ball.

Research your tree’s mature height and spread; place it to visually balance and frame your home while not crowding it. If you want a Live Oak for a small lot, try a Sand Live Oak (Quercus geminata), which resembles our treasured Southern Live Oak, but is more “yard sized.” You won’t get those graceful, swooping limbs that offer their embrace, but a Sand Live Oak matures into a quite lovely and long-lived tree.

Other good, large native trees include:  Shumard Oak (Quercus shumardii), Nuttall Oak (Quercus texana), Willow Oak (Quercus phellos), Red Cedar (Juniperus virginiana), Pond Cypress (Taxodium ascendens). See our range of beautiful native Alabama trees here: https://www.aces.edu/wp-content/uploads/2019/03/ANR-0509_KeyToNativeCommonTrees_042321L-REVISION.pdf

Trees are investments. Plant them right!

1.      Be mindful of where your underground utilities are. Call 811 to check for utilities before planting trees.

2.      Dig hole 2-3 times as wide as the root ball and never deeper than the root ball height. (Think flat Wok, not stock pot.) 

3.      Untangle roots girdling root ball and set ball on firm ground, the top slightly above grade so it doesn’t settle below grade.

4.      Fill hole with the excavated soil, lightly tamping.

5.      Stake tree. 

6.      Water deeply, 2 gallons per inch of trunk diameter, and water often the first month, tapering off to monthly, depending on rain/drought conditions.

7.      Cover root zone with 2-3 inches of mulch, never piled against the trunk, which causes insect damage.

For more detailed instructions, visit: https://www.aces.edu/blog/topics/lawn-garden/proper-tree-planting/#:~:text=   

Catch November’s Ask a Master Gardener for “Small Trees for Urban Landscapes” for your yard. Now, go hug a tree.

Oaks in Washington Square by Joe Eiland.

Live Oaks photo by Joe Eiland.

American Holly photo by Brenda Bolton.