Blue Oak

Quercus douglasii

Physical Characteristics

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.

Distribution

South-western N. America - California.

Habitats

Woodland Garden Canopy;

Edible Uses

Edible Parts: Seed Edible Uses: Coffee Seed - cooked[257]. The seed has been used as a staple food by some native North American Indian tribes[257]. Somewhat sweet[62, 4, 105, 161]. A good size, to 25mm long and wide[82, 200]. 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.

Medicinal Uses

Astringent Dysentery Poultice Skin Any galls produced on the tree are strongly astringent and can be used in the treatment of haemorrhages, chronic diarrhoea, dysentery etc[4]. A poultice of the ground galls and salt has been used in the treatment of burns, sores and cuts[257]. It has also been used as a wash for sore eyes[257]. The leaves have been chewed as a treatment for sore throats[257].

Known Hazards

None known