Blue Oak
Quercus douglasii
Family: Fagaceae
What it is like
Bloom Color: Brown. Main Bloom Time: Early spring, Late spring, Mid spring. Form: Rounded, Spreading or horizontal.
Quercus douglasii is a deciduous Tree growing to 12 m (39ft 4in) at a slow rate. See above for USDA hardiness. It is hardy to UK zone 7 and is not frost tender. It is in flower in May, 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 dry or moist soil. The plant can tolerates strong winds but not maritime exposure.
Height (m): 12
Where it is found
Dry soils in valleys, rolling hills and lower mountain slopes to 1350 metres, often forming extensive stands.
South-western N. America - California.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 3
Seed - cooked. The seed has been used as a staple food by some native North American Indian tribes. Somewhat sweet. A good size, to 25mm long and wide. 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 from some trees 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. A poultice of the ground galls and salt has been used in the treatment of burns, sores and cuts. It has also been used as a wash for sore eyes. The leaves have been chewed as a treatment for sore throats.
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.
Poultice: A moist, usually warm or hot, mass of plant material applied to the skin in the treatment of burns etc.
Skin: Plants used in miscellaneous treatments for the skin.
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. The branches have been used to make rims for twined work baskets. The acorn meal has been used to mend cracks in clay pots. The seed cups are used as buttons. Wood - hard, heavy, strong, brittle. It has a strong cross-grain and is difficult to split. Of little commercial value, it is used mainly for fuel.
Adhesive: Glues.
Basketry: Plant used in making baskets and other items such as chairs. Includes plants that are only used as an ornamental addition.
Buttons: Plants that can be used as buttons. Not including making buttons from wood.
Fuel: Usually wood, plant materials that have been mentioned as being a good fuel.
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.
Food Forest: Plants for Edible Forest Gardens and Food Forests.
How it is grown
Landscape Uses:Border, Erosion control, Massing, Screen, Specimen, Street tree. Prefers a good deep fertile loam which can be on the stiff side. Young plants tolerate reasonable levels of side shade. Tolerates moderate exposure, surviving well but being somewhat stunted. Prefers warmer summers than are usually experienced in Britain, trees often grow poorly in this country and fail to properly ripen their wood resulting in frost damage overwinter. A slow-growing but long-lived tree. Seed production is cyclic, a year of high yields being followed by 2 - 4 years of low production. The tree flowers on new growth produced in spring, the seed ripening in its first year. This species is notably resistant to honey fungus. Hybridizes freely with other members of the genus. Intolerant of root disturbance, trees should be planted in their permanent positions whilst young. Special Features: North American native, Inconspicuous flowers or blooms.
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: 8-11
Growth: Slow
Soil: Medium, heavy (clay)
Shade: Semi-shade, no shade
Moisture: Dry, moist