Why is cork so thick and spongy? © Getty Images

Why is cork so thick and spongy?

Cork oak trees, or Quercus subers, are commercially stripped from their spongy, durable coats - but what gives them this property?

Asked by: Anonymous

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Cork comes from the cork oak tree Quercus suber. The cork is just the very thick outer layer, called the cambium, and is mainly composed of a waxy rubbery substance called suberin. Although the cork is waterproof, unpalatable and insulating, cork trees can survive perfectly well without it. Commercially, cork trees are stripped of their bark every 9-12 years and can be harvested up to a dozen times in their lifetime. It seems that in the wild, the cork is an adaptation against fire. By protecting the trunk and the large branches, the cork oak can immediately resprout its leaves and continue growing after a forest fire. This gives it a selective advantage over other species that must grow back from a stump or regenerate from buried seeds.


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