Great Design Plant: Cork Oak
Witness an incredible renewable resource being grown while lolling in the abundant shade of this expansive, ever-popular tree
There are trees that come and go in the garden — some as passing design whims, others as total landscape failures — but the majestic oak is the 100-year house of trees, worth keeping a home in the family for.
Topping my list of oaks to cherish is cork oak (Quercus suber). Cork oak has played a critical role in human history, due to its namesake bark, and as a long-lived ornamental landscape specimen, it's sure to stand out in present and future gardens.
Topping my list of oaks to cherish is cork oak (Quercus suber). Cork oak has played a critical role in human history, due to its namesake bark, and as a long-lived ornamental landscape specimen, it's sure to stand out in present and future gardens.
Distinguishing traits. Oaks are distinguished by picturesque habits and spreading branches, only becoming more appealing with age. Cork oak is no different and in many ways is a very typical oak tree — with the exception of its unique burly bark. While the deeply furrowed and ridged bark can appear forbidding at first, its texture is surprisingly soft and spongy — much like that of a wine cork.
Glossy green leaves 3 inches long cover the branches of cork oak year-round. Small and delicate male and female flowers appear on the tree in early spring. Pollinated by wind, dainty acorns follow.
Glossy green leaves 3 inches long cover the branches of cork oak year-round. Small and delicate male and female flowers appear on the tree in early spring. Pollinated by wind, dainty acorns follow.
How to use it. It's likely you'll see cork oaks planted as street trees or used in other public landscapes — which should serve as proof of their resilience and longevity.
In the residential garden, escape the hot summer sun in the shade provided by cork oak's pendulous branches. They're a garden feature that adds weight and substance to a garden design.
In the residential garden, escape the hot summer sun in the shade provided by cork oak's pendulous branches. They're a garden feature that adds weight and substance to a garden design.
While most cork oaks grown outside of Mediterranean Europe are used strictly for decoration, cork oaks are still grown for the practical purpose of harvesting cork to plug wine bottles (although that need is steadily decreasing with the introduction of synthetics and cork alternatives).
The bark of the cork tree is harvested by hand after the tree has reached 25 years of age, and this process is repeated every 10 years for the rest of the tree’s lifetime. The trees are not damaged in the process, and afterward they somewhat resemble a sheep that’s been sheared (shown here). Carbon is used for bark regeneration, so trees that are routinely harvested absorb an exponentially greater amount of carbon.
Photo by Wikimedia Commons users Fritz Geller-Grimm and Felix Grimm
The bark of the cork tree is harvested by hand after the tree has reached 25 years of age, and this process is repeated every 10 years for the rest of the tree’s lifetime. The trees are not damaged in the process, and afterward they somewhat resemble a sheep that’s been sheared (shown here). Carbon is used for bark regeneration, so trees that are routinely harvested absorb an exponentially greater amount of carbon.
Photo by Wikimedia Commons users Fritz Geller-Grimm and Felix Grimm
Planting notes. Cork oak has an extremely long life — up to 250 years — and is slow growing. When you plant, keep in mind that your tree has the potential to spread 60 feet up and out, so leave plenty of room for it to grow.
Plant in full sun to light shade and water deeply but infrequently. While cork oak is tolerant of moist soils, it prefers good drainage. Cork oaks develop a deep taproot once established, so avoid transplanting.
Gardeners in California and Oregon must be aware of and sensitive to sudden oak death. Cork oak has yet to make the list of host and associated host plants, but it's important to keep an eye on its health. With all the time and space you'll devote to this tree, it would be quite a blow to lose it.
Plant in full sun to light shade and water deeply but infrequently. While cork oak is tolerant of moist soils, it prefers good drainage. Cork oaks develop a deep taproot once established, so avoid transplanting.
Gardeners in California and Oregon must be aware of and sensitive to sudden oak death. Cork oak has yet to make the list of host and associated host plants, but it's important to keep an eye on its health. With all the time and space you'll devote to this tree, it would be quite a blow to lose it.
Common name: Cork oak
USDA zones: 8 to 10 (find your zone)
Water requirement: Light to moderate
Light requirement: Full sun
Mature size: 30 to 60 feet tall and wide
Benefits and tolerances: Drought and wind tolerant; fire resistant; slope stabilizer
Seasonal interest: Flowers in spring; ornamental bark; evergreen
When to plant: Plant seedlings in spring (protect trees from rodents until mature)