Cork Oak
Quercus suber
Family: Fagaceae
What it is like
Quercus suber is an evergreen Tree growing to 20 m (65ft) by 15 m (49ft) at a slow rate. See above for USDA hardiness. It is hardy to UK zone 8 and is frost tender. It is in leaf all year, in flower from May to June, and the seeds ripen in October. The species is monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and is pollinated by Wind. Suitable for: medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil. The plant can tolerates strong winds but not maritime exposure.
Height (m): 20
Where it is found
Siliceous hills on the littoral.
S. Europe to N. Africa.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 2
Seed - cooked. A famine food. It can be dried, ground into a powder and used as a thickening in stews etc or mixed with cereals for making bread. The seed contains bitter tannins, these can be leached out by thoroughly washing the seed in running water though many minerals will also be lost. Either the whole seed can be used or the seed can be dried and ground it into a powder. It can take several days or even weeks to properly leach whole seeds, one method was to wrap them in a cloth bag and place them in a stream. Leaching the powder is quicker. A simple taste test can tell when the tannin has been leached. The traditional method of preparing the seed was to bury it in boggy ground overwinter. The germinating seed was dug up in the spring when it would have lost most of its astringency. The roasted seed is a coffee substitute. One reader noted the Q. suber population of the Mamora forest in Morocco contains only sweet acorns and can be eaten raw, it has a similar taste to raw chestnuts. The skin removes quite easyl Quercus ilex also exists with tannin-free acorns in the moroccan forests, the locals say around 20 percent are sweet.
Seed: includes nuts, cereals, peas and beans.
Coffee: the various substitutes that can be used instead of coffee.
Medicine
Rating: 2
Any galls produced on the tree are strongly astringent and can be used in the treatment of haemorrhages, chronic diarrhoea, dysentery etc.
Astringent: Produces contraction in living tissue, reducing the flow of secretions and discharges of blood, mucus, diarrhoea etc.
Dysentery: Used in treating dysentery - an infection of the intestines that causes diarrhoea containing blood or mucus.
Other
Rating: 4
A mulch of the leaves repels slugs, grubs etc, though fresh leaves should not be used as these can inhibit plant growth. Oak galls are excrescences that are sometimes produced in great numbers on the tree and are caused by the activity of the larvae of different insects. The insects live inside these galls, obtaining their nutrient therein. When the insect pupates and leaves, the gall can be used as a rich source of tannin, that can also be used as a dyestuff. A fairly wind-tolerant tree, it can be used in shelterbelt plantings. Good on dry banks. Shade tree. Bark is the source of cork, it is much used for heat and sound insulation, flooring, floats etc. Trees are first harvested when they are 25 - 30 years old, and then harvested every 6 - 12 years. The bark must be removed carefully so as not to harm the tree. A large tree can yield up to 1 tonne of cork. On a 10% moisture basis, the bark contains 16.9% tannin. Wood.
Cork: Including any plants used as a cork substitute. Cork is used for insulation (sound or heat), fire-retardant, bottle stops etc.
Fodder: Food given to the animals (including plants cut and carried to them) rather than forage for themselves.
Repellent: Plants that are said to deter but not necessarily kill various mammals, birds, insects etc.
Shelterbelt: Wind resistant plants than can be grown to provide shelter in the garden etc.
Tannin: An astringent substance obtaied from plants, it is used medicinally, as a dye and mordant, stabilizer in pesticide etc.
Wood: A list of the trees and shrubs that are noted for having useful wood.
Fodder: Mast: Fruits and seeds of shrubs, woody vines, trees, cacti, and other non-herbaceous vegetation available for animal consumption.
Industrial Crop: Cork: The inner bark of a tree. Uses include bottle stoppers, insulation, soundproofing, shoe cushions.
Industrial Crop: Tannin: Occur generally in the roots, wood, bark, leaves, and fruit of many plants. Used in tanning leather, dyeing fabric, making ink, and medical applications.
Management: Standard: Plants grow to their standard height. Harvest fruit, seeds, or other products. Non-Destructive management systems.
Other Systems: Dehesa: A fodder tree silvopasture system with livestock grazing on tree crops - nuts, fruit, acorns, woody pods, fodder.
Other Systems: Strip intercrop: Tree crops grown in rows with alternating annual crops.
Regional Crop: These crops have been domesticated and cultivated regionally but have not been adopted elsewhere and are typically not traded globally, Examples in this broad category include perennial cottons and many nuts and staple fruits.
Fodder: Mast: Fruits and seeds of shrubs, woody vines, trees, cacti, and other non-herbaceous vegetation available for animal consumption.
Industrial Crop: Cork: The inner bark of a tree. Uses include bottle stoppers, insulation, soundproofing, shoe cushions.
Industrial Crop: Tannin: Occur generally in the roots, wood, bark, leaves, and fruit of many plants. Used in tanning leather, dyeing fabric, making ink, and medical applications.
Management: Standard: Plants grow to their standard height. Harvest fruit, seeds, or other products. Non-Destructive management systems.
Other Systems: Dehesa: A fodder tree silvopasture system with livestock grazing on tree crops - nuts, fruit, acorns, woody pods, fodder.
Other Systems: Strip intercrop: Tree crops grown in rows with alternating annual crops.
Regional Crop: These crops have been domesticated and cultivated regionally but have not been adopted elsewhere and are typically not traded globally, Examples in this broad category include perennial cottons and many nuts and staple fruits.
Carbon Farming: Plants that can be a critical part of the solution to climate problems. The Carbon Farming Solution - Eric Toensmeier.
How it is grown
Prefers a good deep fertile loam which can be on the stiff side. Lime tolerant. Young plants tolerate reasonable levels of side shade. Tolerates moderate exposure, surviving well but being somewhat stunted. Cultivated for its bark in Europe, it is the main source of cork. Trees are first harvested when they are 25 - 30 years old and are then harvested on a 10 - 12 year rotation. Only hardy in the milder areas of Britain, it is not very frost resistant. Trees grow well in Cornwall where there are many large specimens. Trees grow quite well at Kew. Transplants badly unless it is moved regularly, it should only be moved in September or as growth commences in late spring. Does not fruit well in Britain. Most of the trees grown in Britain as Q. suber are in fact Q. suber occidentalis. Hybridizes freely with other members of the genus. This species is notably resistant to honey fungus. Heat Zone: 9-7.
Propagating it: Seed - it quickly loses viability if it is allowed to dry out. It can be stored moist and cool overwinter but is best sown as soon as it is ripe in an outdoor seed bed, though it must be protected from mice, squirrels etc. Small quantities of seed can be sown in deep pots in a cold frame. Plants produce a deep taproot and need to be planted out into their permanent positions as soon as possible, in fact seed sown in situ will produce the best trees. Trees should not be left in a nursery bed for more than 2 growing seasons without being moved or they will transplant very badly.
Best place to grow: Woodland Garden Canopy;
Habit: Tree
Hardiness: 7-10
Growth: Slow
Soil: Medium, heavy (clay)
Shade: Semi-shade, no shade
Moisture: Moist