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Plant of the Week
Willow Oak
Latin: Quercus phellos
Size matters. If there is room in the landscape, one should always plant
trees that will reward one with grand stature and become a lasting monument to
the person who had the forethought to plant them. One of the grandest of these
big trees is our native willow oak.
Several trees share the title as recordholder for the species, with the closest
in Memphis, Tenn., at 123 feet tall with a spread of 100 feet.
The willow oak is native to bottomland forests across a broad swath of the
southeastern U.S. from southwestern Oklahoma, across the lowlands of Arkansas to
Florida and north as far as southern New York. It is unlike most oaks in that
the leaves are willow-like in shape. The leaves are about 3- to 4 inches long
and about three-quarters of an inch across and completely lack all evidence of
lobes. The leaf is tipped with a single bristle indicating it is a member of the
red oak group. For such a large tree, the acorns are one of the smallest of the
genus and usually measure about one-half inch long and wide.
By naming things we are supposed to -- at least in theory -- reduce confusion,
but with plants, name confusion is one of the things you just have to deal with.
The name willow oak fits this tree nicely because the leaf looks more like that
of a willow than it does most oaks. But the leaf also looks like a fountain pen,
so south of the Arkansas River the tree is often called the "pen oak." This
creates real confusion because the pin oak, Quercus palustris, is also a common
landscape tree.
The species name "phellos" is Latin for cork -- apparently because old trees
have a thick corky bark. However, it should not be confused with the real cork
oak, Q. suber, which is an evergreen oak from southern Europe that produces the
cork of commerce.
People often ask for fast-growing shade trees, but that trait should be way down
on the list of criteria used when selecting a shade tree. Willow oaks are in the
medium growth rate group with trees such as pin oaks, red maples, sweet gums and
green ash. It averages about two feet of growth a year once established.
Thirty-year-old trees here in Fayetteville on upland sites are about 50 feet
tall with a trunk diameter of about 15 inches.
As a landscape tree, willow oaks are best suited to larger sites, public parks
or along roadways. It is the grandest tree in many of Little Rock’s public parks
and is used throughout the city as a street tree. Willow oak leaves are yellow
in the fall and quickly dislodge themselves from the tree, not hanging on over
winter like the pin oak. The leaves make great landscape mulch and are not as
apt to smother the lawn as other oaks if one is tardy about raking the leaves in
the fall.
Willow oaks transplant readily and will grow in a wide array of soils. However,
they grow faster and to a larger size in bottomland sites or areas with
reasonably fertile conditions. Once established they tolerate drought well.
By: Gerald Klingaman, retired
Extension Horticulturist
- Ornamentals
Extension News -
January 21, 2000
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