Outer Trunk

Continuing outwards from the central pith, past the heartwood and sapwood is the cambium, a thin layer of cells that divide to cause secondary growth, i.e. trunk thickening.

As these cells split they replace both the sapwood (xylem) cells on the inside and the inner bark (phloem) cells on the outside.

Cell growth in the cambium is triggered by hormones called auxins that originate in springtime buds and travel through the leaves and inner bark.

The inner bark’s main job is to distribute sugary sap and other organic compounds produced during in leaves during photosynthesis. It has a short life before becoming part of the outer bark’s cork.

Outer bark is a bit like skin, shielding the sensitive inner tree by regulating temperature and moisture levels while providing protection from insects, other wildlife and the elements.

Bark’s use is incredibly varied, including in the production of rope, baskets, capes, mats, latex, cinnamon, certain poisons and even canoes.

Most inner barks are safe to eat too, making it a good emergency food. Apparently bark bread is a thing. Who knew?

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Image: ScienceFacts.net