The Cupressaceae family, includes some of the world’s most ancient trees, some dating back to over 150 million years ago. Famous members of this family include the coastal redwood, giant sequoias, and bald cypress. The redwoods and sequoias certainly have their claim to fame, but what is so special about bald cypress trees?
In addition to the bald cypress being the state tree of the beautiful state of Louisiana and being exceptionally well adapted to moist environments, these trees have unique features at their trunks. Figure 1 shows knob-like structures, called knees, protruding from the near the base of the cypress. Knees are commonly seen growing out of shallow water banks or supersaturated soil.
Christopher H. Briand published Cypress Knees: an Enduring Enigma after inspecting over 200 years of investigations. His thorough analysis can be found here (http://arnoldia.arboretum.harvard.edu/pdf/articles/2000-60-4-cypress-knees-an-enduring-enigma.pdf) ; spoiler- there is no known purpose! It’s been thought that the knees aid in collecting oxygen, nutrients, or storing carbohydrates. The knees may also provide a mechanical function, further anchoring these swamp trees into the muddy soil. Eventually, each of these theories was debunked by laboratory analysis or on-site knee removal.
These trees play an instrumental role in mitigating soil erosion and floodwaters. If they want to keep their knees a secret, will let them for now.
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