Mysterious cypress knees

Pond Cypresses (Taxodium ascendens) are tall coniferous trees that occur in wetland areas of the southeastern United-States, from Virginia to Louisiana. Shallow water dwellers, they can reach up to 25 m in height and typically live up to 1,000 years, although the oldest known specimen was 3,500 years old. Christened “The Senator”, it stood in Big Tree Park, Longwood, Florida, until a fire burned it down in 2012.

The most striking feature of this tree species is its ability to grow vertical, conical woody root extensions above ground and water levels. The role of these “cypress knees” remains a mystery, although various theories exist including aeration, methane emission and mechanical support. Their height depends on the water depth around the tree and their size is conditioned by soil type, soft (larger knees) or firm (smaller knees).

Pond cypresses were introduced in France in 1789 and the trees from the above pictures pertain to the Arboretum de la Vallée aux Loups. Situated south of Paris, this small park owes its reputation to its remarkable trees and its location adjacent to the Maison de Chateaubriand, a mansion which belonged to the eminent French writer of the same name.

If interested in learning more about cypress knees, here is an interesting and thorough article.

Location: Châtenay-Malabry, France

2 thoughts on “Mysterious cypress knees

  1. These are fascinating!
    I find myself leaning towards the mechanical support theory more, but cannot fully commit. Maybe these provide obstacles for herbivores so they cannot get close to the main trunk and eat the bark?

    Liked by 1 person

  2. Hi Le, thx for commenting 🙂 It’s pretty amazing indeed, I bet it must be great to see these trees in their homeland. Your theory sounds interesting, it does look like a natural defensive barrier. Some say another possibility is that the knees developed under some past environmental pressure and have lost their utility nowadays. Maybe they’ll figure it out one day!


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