15 Sep Tree of the Year 2021: Cork oak on Fourth Street
Where do wine bottle corks come from?
Photo essay published in 2022.
Where do wine bottle corks come from? From Cork oak trees, of course! In fact, about three-quarters of cork bark harvested goes into making wine bottle stoppers. You will know a lot about Cork oaks by the time you finish this photo essay.
Ashland Trees of the Year
I decided to skip ahead to the 2021 Tree of the Year, announced at the April 7, 2022 Tree Commission meeting. It is a Cork oak tree located at 233 Fourth Street in Ashland.
The wisdom of arborist Casey Roland
I met arborist Casey Roland at the tree on July 1, 2022. He told me that Quercus suber (Cork oak) is one of his favorite trees. He said, ” There are only a few in the valley, and only a couple in town. The cork oak on Fourth Street is probably the biggest and maybe the oldest I can recall locally. They aren’t really stately until they reach maturity. Like most oaks, they tend to be gangly puppies, but are beautiful dogs! The name comes from the bark of course, and yes, that is where wine bottle corks come from.”
As we looked up at the tree, he pointed out where a major limb had been cut off due to the power lines above the tree. Aside from this, the tree appears to be very healthy.
How old is our Cork oak?
Our new Tree of the Year is located in the park row on Fourth Street. Since Fourth Street was laid out around the time the first train arrived in Ashland May 1884 (138 years ago), I wondered how old this tree might be. Based on the size of the tree, Casey thinks it is about 80 years old. This means it may have been planted in the early 1940s.
The most surprising fact about Cork oaks
The biggest surprise for me was learning how Cork tree bark is harvested. The photo above shows a Cork oak forest after harvest. After a tree is more than 25 years old, the bark is stripped off using a traditional axe and a simple manual process that has been the same for hundreds of years. Does this kill the tree? No!
Cork oaks are unique in that they regrow their bark, which may be 5 inches to 10 inches thick. Not only that, the bark can be harvested again after 9 to 12 years. Not only that, the quality of cork from the bark improves as the tree gets older. Amazing. Since Cork oaks commonly live to be 200 years old, each tree may be harvested for its cork bark between 14 and 19 times!
Oldest and largest Cork oak tree
The oldest and largest Cork oak known grows in Aguas de Moura, Portugal. Planted in 1783 or 1784, it has been harvested for wine corks every nine years since 1820! The 2009 harvest, for example, yielded 825 Kg (1,818 pounds) of raw cork. When processed, this one tree produced enough wine bottle corks for 100,000 wine bottles! That’s about 25 times as many as an average cork oak produces from one harvest of its bark.
This Cork oak is called the Whistler Tree because of the countless songbirds that fill its canopy.
It is fitting that the world’s oldest Cork oak grows in Portugal. This country has the greatest area of Cork oak forests and is the world’s leading producer of cork products. Spain is second to Portugal in forest area and cork production. The North African countries of Morocco and Algeria are also large producers of cork.
The “average” Cork oak tree
Most Cork oaks grow to 50 feet to 60 feet in height, and live up to 200 years. As mentioned above, the bark is first harvested when the trees are at least 25 years old. It comes off in large strips, which are first dried in the sun for about six months and then boiled so they can be flattened for further use.
Cork is filled with air cells – the majority of cork is actually the air trapped within the cell walls. Cork is light, watertight and flexible. According to the WE Cork website, “Every cubic inch of cork has more than 200 million completely enclosed air cells, each measuring 1/1000 inch in diameter. These minute cells have 14 sides, virtually eliminating empty spaces between the cells. Since 50% of cork is filled with air, it essentially acts as an “air cushion”, absorbing vibrations and direct impacts. This makes it an excellent acoustic and soundproofing material for floors, walls and ceilings.”
Other than wine bottle stoppers, there are many other uses for cork: natural building insulation, natural flooring, acoustic and soundproofing material – and some of you may remember cork in the footbed of original Birkenstock sandals, which were introduced into the U.S. in 1966.
A short history lesson
According to the Cork Quality Council website, “Natural cork has been associated with the storage of valuable foods and beverages for thousands of years. Ancient Egyptians, Greeks and romans referenced cork as a preferred material for stoppers used with wine and olive oil.”
Especially for ham lovers
Laura Lukes writes, “In addition to providing cork bark, cork oak groves in Portugal and Spain support another form of agriculture: their acorns provide sustenance to sheep, cattle, and especially hogs. A superior type of ham with a distinctive sought-after flavor is obtained from the Iberian pigs that feed on the fallen acorns.”
And finally, a short ecology lesson
According to the Word Wildlife Fund, “Cork oak landscapes are one of the best examples of balanced conservation and development anywhere in the world. They also play a key role in ecological processes such as water retention, soil conservation, and carbon storage.”
Anon. “Cork Oak, Quercus suber.” September 15, 2012, Rainforest Alliance website.
Anon. Cork Quality Council website. [accessed 9/9/2022]
Anon. “12 Facts about Cork Trees,” February 13, 2015, Ganau America website. [accessed June 2022]
Lukes, Laura. “Local Trees: The Cork Oak,” The Real Dirt Blog, August 9, 2019.
Roland, Casey. Interview and personal communication, May-July 2022.