Quercus engelmannii

What to Eat

Edible parts: Gum, Seeds

The acorn, up to 25mm long and 12mm wide, must be cooked and was used as a food source when better options were scarce. It can be dried and ground into flour for thickening stews or mixing with cereals for bread. The seeds contain bitter tannins that need to be leached out by washing thoroughly in running water, though minerals are also lost. Whole seeds may take several days or weeks to leach properly; a cloth bag placed in a running stream is one traditional method. Ground meal leaches faster. A taste test confirms when enough tannin has been removed. Traditionally, seeds were buried in boggy ground over winter and dug up in spring once most of the astringency had gone. The roasted seed serves as a coffee substitute. The bark gum can be pounded, washed, and chewed like chewing gum.

Where to Find It

It is a temperate plant. National Arboretum Canberra.

Australia, Mexico, North America, USA,

How to Identify

Quercus engelmannii is a frost-tender evergreen tree reaching 10 m tall, growing at a medium rate. It maintains foliage year-round, flowering in May with seeds maturing in October. The species is monoecious and wind-pollinated. It thrives in loamy or clay soils across mildly acidic to mildly alkaline pH ranges, tolerating semi-shade or full sun. It prefers moist soil and withstands strong winds but not salt spray exposure.

How to Grow

We have very little information on this species and do not know if it will be hardy in Britain, though judging by its native range it should succeed outdoors at least in the milder areas of the country. The following notes are based on the general needs of the genus. 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. Intolerant of root disturbance, trees should be planted in their permanent positions whilst young. Hybridizes freely with other members of the genus. Plants in this genus are notably resistant to honey fungus.

Propagation: Acorns lose viability quickly if allowed to dry out. They can be stored moist and cool over winter, but are best sown as soon as ripe in an outdoor seed bed with protection from mice and squirrels. Small quantities can be sown in deep pots in a cold frame. Because plants develop a deep taproot early, they should be moved to permanent positions as soon as possible — seed sown in situ produces the best trees. Do not leave trees in a nursery bed for more than 2 growing seasons, as they transplant very poorly after that point.

Medicinal Uses

Any galls that form on the tree are strongly astringent and have been used in the treatment of haemorrhages, chronic diarrhoea, and dysentery.

Other Uses

A mulch of the leaves repels slugs and grubs, though fresh leaves should not be used as they can inhibit plant growth. Oak galls, produced by the larvae of various insects, can be harvested after the insect pupates and leaves — they are a rich source of tannin that also serves as a dyestuff. The wood is very heavy, hard, strong, close-grained, and brittle. It has no commercial value and is used only as fuel.

Quercus engelmannii, the Engelmann oak or Pasadena oak, is a species of oak in the white oak section (Quercus sect. Quercus), native to Southern California and northwestern Baja California, Mexico.

Notes

There are about 600 Quercus species.

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