Cork Oak
Quercus suber occidentalis
Family: Fagaceae
What it is like
Quercus suber occidentalis is an evergreen Tree growing to 18 m (59ft) by 13 m (42ft) 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 and can grow in heavy clay soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers dry or moist soil. The plant can tolerates strong winds but not maritime exposure.
Height (m): 18
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.
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: 2
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. 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. Wood.
Cork: Including any plants used as a cork substitute. Cork is used for insulation (sound or heat), fire-retardant, bottle stops etc.
Repellent: Plants that are said to deter but not necessarily kill various mammals, birds, insects 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.
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. This sub-species has slightly thinner bark than the species.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. This sub-species is somewhat hardier than the type. Trees grow well in Cornwall where there are many large specimens. There is at least one large healthy specimen of this tree at Kew, it produced some seeds in the hot summer of 1989. 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 this sub-species. Hybridizes freely with other members of the genus. This species is notably resistant to honey fungus.
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: Dry, moist
Things to keep in mind
Its other names
Local names
Synonyms
Q. occidentalis.