Editor’s Note: This week we feature another tree from Emina Darakjy, a very knowledgeable tree enthusiast we are lucky to call a Buzz contributor. When we started this feature, we had just reported on the latest loss of a mature street tree. We hope these columns, featuring trees that will do well in our neighborhoods, will inspire readers to plant new trees. Planting a tree is a simple step we can all take to combat climate change and improve the quality of life in our neighborhoods. Please feel free to email at [email protected] us if you have any tree questions for Emina!
The cork oak is a member of the Fagaceae family and is native to Southern Europe and Northwestern Africa.
The botanical name “Quercus suber” is derived from the Latin words: “Quercus” for oak tree and “suber” for cork. This is a medium-sized evergreen tree that can reach a height of 40 to 50 feet with a spreading canopy up to 60 feet wide. It can live for more than 200 years.
The trunk is very unusual looking, with a light grayish-brown thick layer of spongy bark with vertical fissures that are white on the outside and reddish-brown on the inside. The trunk is the main characteristic feature of this tree.
In some countries like Spain, Portugal and Morocco where very large forests of cork oak exist, this tree is grown for the sole purpose of producing, harvesting and commercially selling cork which is a natural product used to make wine bottle stoppers as well as all types of flooring, insulation, and household articles.
The harvesting of the cork begins when the tree is about 20 years old and continues in intervals of 9 to 10 years. This is done by making a cut to the layer of bark that covers the trunk and stripping it away. This does not kill the tree or cause any damage to it. After the stripping is done the trunk looks smooth and reddish brown then turns darker and starts growing another layer of bark. This process continues for more than 100 years.
The leaves are alternate, ovate, serrated, and glossy dark green on the top. Also, the leaves are very pale gray with distinct hairy veins underneath.
The acorns of the cork oak are oblong with beautiful cream-colored frilly caps that cover as much as one third of the acorns.
Once established the cork oak is considered drought-tolerant but can benefit from occasional deep watering. It does well in most types of soil with good drainage and prefers full sun but can tolerate some shade.
The cork oak in California is grown as an ornamental tree, and requires a larger parkway/cutout of 7-feet. It can be planted as a street tree, in a park or in one’s garden with ample space. Damage to the sidewalks from its roots is minimal.
Pest to worry about are root diseases, California oak worm and the polyphagous shot hole borer (PSHB).
When using mulch, please make sure to keep it away from the tree trunk and redirect your sprinkler heads away from the trunk. Using drip irrigation is the preferred solution to watering trees. Lastly, never put decorative arroyo boulders or stones underneath the tree as this tends to cause compaction to the soil and keep it very moist which is not a good thing for any tree and especially not the oak species.
On a side note, I was fortunate to grow up near one of the largest cork oak forests in the world called the Mamora Forest, outside of Rabat, the Capital of Morocco. I have very fond memories of piling up in the family car every Sunday to go for a picnic underneath these remarkable trees and surrounded by carpets of beautiful flowers.
Emina Darakjy is a past president of Pasadena Beautiful and its present Tree Program Chair. Darakjy says she has always had a passion for trees and that she is involved with several other tree organizations such as California Re-Leaf, the Arbor Day Foundation and American Forests. She is a past president of Street Tree Seminar Inc. and the present president of the California Urban Forests Council.
One thought on “Meet This Tree: Quercus suber – Cork Oak”
Many thanks to Emina Darakjy for upping our arboreal IQs.
I can’t recall seeing a cork oak in the neighborhood. Can anyone point me to one?
Our leafy neighborhood cries out for tree knowledge. What are the five best, and five worst, trees to plant in the parkway? What trees stand out as multi-stems? What trees are ideal for lawns? What trees are lowest maintenance? What trees look best in particular seasons of the year? What trees are the best and worst for root damage? What trees are currently in vogue with landscape designers? What trees are especially drought tolerant? When is it time to think about replacing an old tree? Persons of average intelligence are starving for information.