January 26, 2023

The Cork Bark Lifecycle

The Cork Bark Lifecycle

Cork is one of the world's under-appreciated renewable resources. Each cork tree planted plays a vital role in reducing CO2 in our air and releasing pure O2 for us to breathe. While it performs this crucial process, the tree is hiding its biggest secret in plain sight. 

The cork oak tree is one of the few trees that can survive its bark being harvested. In fact, the cork oak tree doesn't just survive harvesting; it actually thrives. When its bark is harvested, the tree kicks on the afterburners, so to speak. The tree increases the amount of CO2 it absorbs and turns that photosynthetic energy into regrowing the bark. 


But what happens to the bark once it's harvested?


So, we need to begin by learning about what life is like as a Cork Oak Tree. Cork trees are primarily planted in the warm and temperate regions of the Mediterranean. Unlike many of the dense growth forests found in North America, the trees have plenty of space and are surrounded by vast grasslands.


A cork tree with large cows resting in the shade in a vast grassland


Once the tree is planted, it is left alone to grow and for the bark to thicken. A well-trained cork harvester will keep an eye on the tree and determine when it is ready for its first harvest. This is typically when the tree is around 25 years old. When the tree is ready, the outer bark is carefully peeled away from the tree, leaving the protective inner membrane in place. The tree is then marked with the year of its harvest and left for the bark to regrow. 


Photo of a recently harvested cork tree marked with the number 9


On average, a tree will be harvested every 9 years after its first harvest. As the number of times, its bark has been harvested increases, the tree becomes more efficient at regrowing the bark and can be harvested more frequently. 


A graphic showing the cork bark lifecycle from Harvest to carbon dioxide being absorbed and photo synthesis occurring to oxygen being released and another harvest happening


Each cork tree can live to be more than 200 years old. Its bark can be harvested more than 20 times, and it can remove as much as 20 tons of CO2 from the atmosphere. 


Now let's dig into the lifecycle of the cork bark. The first thing that you should know is that there are two types of bark harvests, the virgin harvest, and the mature harvest. The bark from these harvests is visually different and is used for different purposes. 


Virgin Cork Bark

Virgin cork bark is the bark from the first and sometimes second harvest. This bark looks the most like oak bark you might see in your backyard. This bark is grooved and pitted with lots of character, but the inner cork is thin and inconsistent. 


Virgin cork bark with plants surrounding them in a terrarium


Virgin cork bark is ideal for mounting orchids, use in terrariums, and as specialized wall coverings. When the bark is harvested, it is sorted by what bark is best suited for each product. 


A graphic showing the virgin cork bark lifecycle. From bark to being recycled to being cork granules


Mature Cork Bark 

When the bark regrows after the virgin harvest, it looks pretty different. Gone are the deep pits and grooves, with a smoother, more uniform exterior in place. The cork's spongey inner cork also looks different; it is much thicker and better developed than the virgin harvest. Ideally, the inner cork of the cork is thick enough to punch out wine corks like this. 


virgin cork bark vs mature cork bark


Cork is processed with a no-waste philosophy top of mind; this means every part of the harvested bark is turned into something, be it fabric, flooring, or the stopper in your favorite bottle. Any pieces that remain are ground into cork granules or cork dust. 


Mature bark lifecycle from bark to finished product to being recycled


One of the questions we get frequently is what happens to recycled corks once they are dropped off. Recycled cork can be turned into more things than you may realize!

Your recycled corks may be donated for elementary school craft projects or ground up and turned into everything from recycled granules to cork sheets!



Want to learn more about the creatures that share the cork forests? Read more about them here!


Have you heard that cork is going extinct? Read more about the myth here!