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Plant of the Week
Blackjack Oak
Latin: Quercus marilandica
This summer’s drought has been tough on trees. The drive
between Fayetteville and Little Rock is punctuated with whole hillsides of brown
and seemingly lifeless trees.
While these trees - mostly oaks, hickories, dogwoods and elms - look bad from a
distance, most will survive the rigors of the 2000 drought without much problem.
Summers like this help one appreciate the really tough trees such as the
blackjack oak.
A kid I knew in my youth was scrappy and always getting into fights. His
favorite saying was, "When you’re ugly you gotta be tough." Mother Nature has
applied this simple truism to the blackjack oak because it is one ugly, but
tough tree.
Blackjacks are found throughout most of the eastern woodlands, occupying sites
with soil too poor or dry for oaks with more stature and substance to flourish.
It was one of the few tree species to venture onto the Great Plains before white
settlement, occupying a region from central Texas northeast through Oklahoma
known as the cross timber region.
The blackjack is a small, gnarly tree usually under 35 feet tall with a round
crown and leathery, three-lobed leaves. It is a member of the red oak tribe and
has the characteristic leaf spine at the end of each lobe. The leaves hang on
the tree through the winter to be pushed off by new leaves the following spring.
It’s trunk is often deeply furrowed and black, giving it a brooding wintertime
appearance.
The Rodney Dangerfield of oaks, blackjacks are given but one use - firewood - by
most authors who seem overly hung up on the notion that all oaks reach the
pinnacle of their glory at the saw mill.
It might be instructive to speculate on the long term effects of this summer’s
drought on the survival and health of the forest. As bad as the trees look, most
will survive the drought because they have been forced into an early dormancy to
conserve water.
Unfortunately, that is not the end of the story. The oaks of our eastern forest
are systemically infected with a fungus called Hypoxylon canker - sort of the
athlete’s foot of the oak kingdom.
Survey work conducted by Dr. Pat Finn at the UofA following the severe drought
of 1980 showed that about 80 percent of the oaks of northwest Arkansas have this
systemic infection. This fungus is usually benign and does no apparent harm, but
droughts cause it to flare up. Certain trees -- with no discernable pattern --
are killed by the multiplying hyphae of the fungus as it produces its spores on
fungal mats under the bark of the tree. These fungal mats push the bark off
which accumulates at the base of the tree like a rain of deadly dandruff.
For the health of the forest, Hypoxylon is a beneficial fungus because it thins
the stand of trees. In 1980, the disease killed about 12 percent of the oaks in
some areas, thus allowing the survivors more opportunity to obtain water.
Unfortunately most of us that build our homes in the woodland have difficulty
taking the long view on ecology when the tree in front of our house is the one
that dies. About all that can be done to ward off the effects of this problem is
to keep the drought at bay by watering before conditions become too severe.
Blackjacks are not in the nursery trade and many who have them on their property
treat them with little respect. But, before dismissing this tough tree as a
scrub oak and relegating it to the woodpile, reflect on its toughness and
adaptability under adverse conditions.
By: Gerald Klingaman, retired
Extension Horticulturist
- Ornamentals
Extension News -
September 22, 2000
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