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

Thursday, April 26, 2007

Bald cypress : Trees with knees

Taxodium distichum, baldcypress


Young baldcypress at Land Between the Lakes, KY

The three young bald cypress trees in the photo above should thrive at the lake's edge. They are already developing the buttressed trunks that are typical of the baldcypress. Before long, their roots will grow beneath the water and begin sending up the woody projections that are called "knees".

Scientists aren't sure what function the knees have. One theory is that the knees are a mechanism to supply oxygen to the roots. Another theory is that the knees help stabilize the tree when it's growing in mucky conditions.

The possibility of knees should be considered when planting a bald cypress in your landscape. If you are planting the tree in a boggy area, knees will almost certainly develop. This could be a problem if you want to mow around the tree. If you are planting the tree in a moist, well-drained area, it will probably never develop knees.

Baldcypress roots don't send up knees unless they are submerged in water at least part of the time. However, bald cypress roots are attracted to moisture and when they find a boggy place, they will send up knees there, even though it may be far from the trunk.

Here's an example of distant knees. I saw a baldcypress tree growing on a riverbank, probably 30 feet above the water. Down at the bottom of the river's little canyon, in the shallow water at the river's edge, the bald cypress roots had grown a little forest of knees.

Wherever you plant your baldcypress tree, keep the soil moist during dry weather. They won't tolerate hard dried-out soil. This is one tree that it will be hard to overwater!

Check out this beautiful, massive old baldcypress, growing in an Arkansas swamp. (Scroll down to the second photo on the page.) Its knees are huge!

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Enrich your life with the study of trees.

"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."

Charles Sprague Sargent (1841-1927)

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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