The cool shade of a big oak is a blessing for any yard. If
you’re looking
for landscape plants to put under it, don’t forget the biggest
thing out there.
"If you’ve got a 30-inch tree, you’re not going to
replace it in one
person’s lifetime," said Kim Coder, a forester with the
University of Georgia
Extension Service.
"You can replace that azalea every year for 30
years," he said.
"But if you mess up the tree, you’re not going to get it
back."
For that reason, tilling the soil under an old oak tree is
"out of
the question," Coder said.
"People will go in under a big oak and till up the place
for azaleas
or flower beds," he said. "And then they’ll wonder why
the tree starts to
decline. Tilling under an oak destroys an awful lot of
roots."
Tilling may be the worst of the things that "go
desperately
wrong," Coder said, when traditional Southern landscaping
and big oaks come together.
Other things that can be just as bad, he said, are those that
happen close
to the trunk.
"People like to put raised beds or big planting boxes
around the base
of the tree," he said. "That often opens the door for
root rot and other
pathogens to get into the tree. It tends to suffocate the roots
under the bed or planter,
too."
The most common mistake is simply overplanting.
"A typical Southern landscape may have a few tall pines
here and
there, some oaks to provide the main canopy, a midstory of
dogwoods, an understory of
flowering shrubs and some bulbs and flower beds," Coder
said. "And there’s
probably some ivy running up some trees.
"But most active roots are very shallow," he said.
"We may
have 60 feet of height in which to arrange plant parts above the
ground. But in the
ground, we’ve only got a foot to 18 inches of depth to stuff
everything into."
The key, he said, is "the ecology of the system."
Simply put,
whatever is in your yard has to divvy up the water, nutrients
and sunlight. And there’s
only so much of that stuff to go around.
"You can water and fertilize the place and increase its
carrying
capacity," Coder said. "But it still has a limit. If
we try to grow too much out
there, the whole landscape will end up looking pretty
sorry."
That doesn’t mean you can’t plant anything under big oaks.
"Lots of things will grow under oak trees and survive and
thrive," he said. "You just want something that’s not
invasive or aggressive —
something that will be polite and just sit there."
If you want grass, extension turf specialist Gil Landry said
the best
choices are St. Augustine in south Georgia and tall fescue in
north Georgia. The
second-best choice is zoysia statewide.
But don’t fertilize it as much under the tree, he said. And
don’t mow it
as short as you normally would. If two inches is the recommended
height, cut it three
inches under the tree.
There may be better choices than turf. Extension
horticulturist Mel Garber
suggests planting a ground cover such as Ophiopogon
japonicus or periwinkle (Vinca
minor).
If you want more striking color, he said, try impatiens,
which thrive in
low, diffuse light. They do need more care, though.
You may want to mulch the area with pine straw, then plant a
few flowering
shrubs and add container plants for summer color.
"Just don’t treat the tree like a big umbrella,"
Coder said.
"It’s a living thing, with needs of its own. And it’s the
most valuable thing out
there."
