Bald Cypress Trees and Their Enigmatic “knees”

May 07, 2021

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Photographer: Patti Weeks 

Summary Author: Patti Weeks 

The Bald Cypress tree (Taxodium distichum), native to the southeastern United States, thrives in the humid climates of the eastern coastal plain from Delaware, down through Florida, over to eastern Texas and up the Mississippi River to southern Illinois. It’s a long-lived, water-loving symbol of the swamp that grows to typical heights of 35–120 feet (10–40 m), with average trunk diameters of 3–6 feet (0.9–1.8 m). However, records list the tallest cypress tree in Virginia at 145 feet (44.11 m), the stoutest in Texas at 39 feet (~12 m) and the oldest living tree in southeastern North Carolina at 2,264 years old. As a testament to their longevity, an underwater bald cypress forest was discovered in 2012 several miles off the coast of Mobile, Alabama, 60 feet below the surface of the Gulf of Mexico. Likely uncovered by Hurricane Katrina in 2005, the well-preserved forest contains trees that are about 52,000 years old and thus most likely lived in the early glacial interval of the last ice age.

The trees pictured here, more average in dimensions, are seen in their normal water level in the Cypress-Gum Swamp area of the 324-acre River Park North, which is adjacent to the Tar River in east-central Greenville, North Carolina. The water level can rise several feet higher after a heavy rain along with the rise in the river level. (If you look closely, you can see the water level mark on the largest tree, made by the 500-year flood of the Tar River as a result of the 1999 Hurricane Floyd.)

Peculiar growths of cypress trees in swamps are “cypress knees” that grow vertically from their roots above the normal water level. Their actual function is unclear, but it’s speculated that they may provide oxygen to the roots (as a possible pneumatophore), allow nutrient accumulation or that they add stability to the wide, buttressed bases of the trees in the soft, muddy soil. While the function of cypress knees continues to be researched, the aeration theory seems to be the most popular.

Photo Details: Top - SONY DSC-RX10 IV camera; 33.51 mm focal length; f/3.5; 1/640 second exposure; ISO 800. Bottom - Same except 90.45 mm focal length; f/4.