Herb: Blue Oak

Latin name: Quercus douglasii

Family: Fagaceae (Beech Family)

Medicinal use of Blue Oak:

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.

Description of the plant:


12 m
(39 feet)


Habitat of the herb:

Dry soils in valleys, rolling hills and lower mountain slopes to 1350 metres, often forming extensive stands.

Edible parts of Blue Oak:

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.

Other uses of the herb:

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.

Propagation of Blue Oak:

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.

Cultivation of the herb:

Dry soils in valleys, rolling hills and lower mountain slopes to 1350 metres, often forming extensive stands.

Known hazards of Quercus douglasii:

None known

Plant information taken from the Plants For A Future.