Curious About Cork?

Much like the coast live oak (Quercus agrifolia) in Ventura County, the cork oak tree (Quercus sitbe) dominates the rolling hillsides around the Mediterranean Sea. The two trees could be twins: Both feature large, sturdy trunks; heavy, spreading branches; and a crown of dense foliage with prickly holly-like leaves. In both ecosystems, oak forests serve an important role of providing food and shelter for animals like foxes and for resident and migrating birds.

The difference between the two lies in the bark: The outer bark of cork oak, known commercially as “corkwood,” is much thicker, more deeply furrowed and more gray than the brown oaks of California.

Corkwood protects the oak from fires which keep down the understory that would otherwise crowd them out. Harvesting corkwood doesn’t hurt the trees during warm, dry weather; rain and cold in fall harms the “naked” trees.

When corkwood is stripped, cork farmers like Ricardo Cecilio in Portugal’s Alentejo take care not to damage the cambium layer that hugs the tree and delivers nutrients. With the bark removed, the pink cambium layer dries and tans, and the tree rapidly replaces the protective layers of cork, about one and a half inches of bark every six years, with wounds to the cambium quickly healing. Harvest can continue sustainably about every nine years for 100 years or more.

Corkwood becomes many products including the classic closures for wine bottles. The highest-grade corks come from the third to sixth harvest from trees 50 to 80 years old, when the corkwood is least porous and most uniform in quality. Portugal produces almost 50% of the world’s corks.

Climate change is having a huge impact, reported Cecilio, especially on young trees. After harvest, “they’re dying. … In winter it doesn’t rain enough and in summer the heat waves are more and more frequent. We had three heat waves during spring this year. It’s getting more and more serious.”

Purchasing wine with a real cork closure preserves a traditional way of life—and an entire ecosystem that helps combat climate change by sequestering carbon.

To see cork oak trees, visit Rancho Camulos on highway 126 near the Ventura County line. One is located near a large barn at the front of the property while a second stands between the grape arbor and schoolhouse. Approximately 100 years old, the cork oaks were likely planted as specimen trees, not for commercial harvest. Three cork oak trees were recently planted at Fillmore’s City Hall in honor of former City Council Member Ari Larsen. For the observant, more cork oak trees can be found throughout the Southland.