Tree Notes is about trees -- especially native trees, trees for wildlife, and trees in history.

Tuesday, June 12, 2007

Leaves of blackjack oak (maybe)

Adventures in leaf identification


I have long-term confusion about some small oak trees along our lane. They grow in tangled thickets of underbrush where it's impossible to even guess how many separate trees there are.

Several times, I've tried to look up their leaves in my books. Every time, I think that they look a lot like bear oak. However, bear oak isn't native here, so I always reluctantly decide on blackjack oak.

Here are leaves from two of these trees, growing near each other. The top row of leaves are from the first tree and the bottom row of leaves are from the second tree. Notice the variation just between the two leaves of the second tree (bottom row.)

The two leaves in the bottom row resemble the two types of leaves I find attributed to the blackjack oak in my reference books. The leaf on the left looks like the blackjack oak leaf in my Audubon field guide*. The leaf on the right is similar to the blackjack oak leaf in Trees and Shrubs of Kentucky*. Thus, the tree from which the bottom two leaves came is probably a blackjack oak -- but I'm still not sure about the other tree.

The books I've consulted also mention a yellowish color and some fuzz along the veins on the underside of the leaf, and bristles. None of the leaves in my photo are fuzzy underneath. And, though they are paler on their underside, I wouldn't call them yellowish. Also, I don't see any bristles on them. But perhaps they'll develop fuzz, color, and bristles as the season advances.

Here's a summary of what I've read about blackjack oaks while once again researching their leaf shape. Blackjack oaks are small scrubby trees with crooked, sturdy branches. Their height is usually less than 40 feet, and often much shorter. They grow in thin soil and dry conditions. They don't like shade, so they are usually found at forest edges or on slopes. All of this is a perfect description of the trees I'm calling blackjacks.

Blackjacks are found throughout much of Kentucky, including my county. They are native to every state in the Southeastern U.S. from eastern Kansas to the Atlantic Ocean. It is interesting to note in a map of their distribution that they do not grow in the Mississippi River valley. I suppose the soil is too rich and damp for them.

Like all oaks, blackjacks have great wildlife value. The acorns are eaten by a wide range of animals and birds, and the leaves, twigs, and bark may be nibbled in some seasons as well.

For biographical info on books I've mentioned in this post, please see the bottom of this column.

2 comments -- please add yours:

drhender said...

Although Blackjack Oaks are native to Kentucky, the leaves you show are definitely not blackjack leaves. Blackjack leaves have less distinct lobes and generally have only 3 of them.

That leaf looks more like a Post Oak leaf, which is also a smallish oak and native to Kentucky.

If you want to know if it is a blackjack oak, here's a suggestion. Blackjacks are a member of the red oak... one of only a few reds that have rounded lobes. Red oak acorns typically take 18-24 months to come to maturity before falling from the tree. They are also quite high in tannins when they first fall, making them very bitter in flavor.

Post oaks are in the white oak family. Their acorns mature in the first summer.

Take a freshly fallen nut and taste the meat inside. If it is bitter, it is a red oak and potentially a blackjack. If it isn't bitter, you can be sure it's a white oak, such as a post oak.

rex said...

yes, the blackjack leaves are bell shaped....

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"The power to recognize trees at a glance without examining their leaves or flowers or fruit as they are seen, for example, from the car-window during a railroad journey, can only be acquired by studying them as they grow under all possible conditions over wide areas of territory. Such an attainment may not have much practical value, but once acquired it gives to the possessor a good deal of pleasure which is denied to less fortunate travelers."

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Print references I frequently consult

Benvie, Sam. Encyclopedia of North American Trees. Buffalo, NY: Firefly, 2000.

Brockman, C. Frank. Trees of North America: A Guide to Field Identification. Ed. Herbert S. Zim. New York: Golden, 1986.

Cliburn, Jerry, and Ginny Clomps. A Key to Missouri Trees in Winter: An Identification Guide. Conservation Commission of the State of Missouri, 1980.

Collingwood, G. H., Warren David Brush, and Devereux Butcher. Knowing Your Trees. Washington: American Forestry Association, 1978.

Dirr, Michael. Dirr's Hardy Trees and Shrubs: an Illustrated Encyclopedia. Portland, Or.: Timber, 1997.

Elias, Thomas S. The Complete Trees of North America; Field Guide and Natural History. New York: Book Division, Times Mirror Magazines, 1980.

Grimm, William Carey. The Book of Trees;. Harrisburg, PA: Stackpole, 1962.

Hightshoe, Gary L. Native Trees, Shrubs, and Vines for Urban and Rural America: a Planting Design Manual for Environmental Designers. New York: Van Nostrand Reinhold, 1988.

Little, Elbert L. National Audubon Society Field Guide to North American Trees. New York: Chanticleer, 1996.

Martin, Alexander C., Herbert S. Zim, and Arnold L. Nelson. American Wildlife and Plants. New York: McGraw Hill, 1951.

Mitchell, Alan F., and David More. The Trees of North America. New York, NY: Facts On File Publications, 1987.

Randall, Charles E. Enjoying Our Trees. Washington: American Forestry Association, 1969.

Settergren, Carl D., and R. E. McDermott. Trees of Missouri. Columbia: University Extension, 1995.

Sternberg, Guy, and James W. Wilson. Native Trees for North American Landscapes: from the Atlantic to the Rockies. Portland: Timber, 2004.

Wharton, Mary E., and Roger W. Barbour. Trees and Shrubs of Kentucky. Lexington: University of Kentucky, 1973.

Wyman, Donald. Trees for American Gardens. New York: Macmillan, 1965.

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