Quercus species


Today the Oaks are best known for their strong, attractive wood (or as the best firewood), but for most of human history they have been far more important as a source of food. Acorns (Oak seeds) have been called the ancestral food for much of humanity and have been a primary source of food for humans almost everywhere they grow; in America, Asia, Africa and Europe. 

Many Native American tribes used acorns for food, but they are probably most associated with those in California. An indication of their importance to these people was the fact that families often held ancestral gathering rights to certain groves of trees. The acorn harvest was a major annual event of their lives and (when the harvest was good) a time for celebration, feasting and dancing (even the men helped gather them). In some places one can still find mortar holes in large rocks, used by generations of women to grind their acorns. These stone mortars were too heavy to move around, so there were permanent ones at each campsite.

Nutrients: Leached acorns contain from 5 ‑ 20% fat, 2 ‑ 5% protein, 50 ‑ 70% carbohydrate and lots of minerals. The unleached nuts are inedible because they contain up to 6% percent tannin. This is quite toxic if ingested in quantity and can damage the liver.

Food: One might imagine that acorns are a subsistence food, eaten out of necessity rather than choice and not very palatable, but this would be quite wrong. Certainly they don’t taste very good in their raw state, but properly prepared acorns are a wholesome and tasty food.

Gathering: In a good year a single Oak tree may give several bushels of acorns and in early autumn it is often possible to gather hundreds of pounds of food in a single day. Watch out for acorns with holes in the shells, as these contain insect larvae and should be discarded. There is an easy test to see if acorns are wholesome, just put them in water. The good ones will sink, the bad ones will float.

Where sweet and bitter acorns grow together they should be gathered separately. Don’t mix them up, as they need different degrees of leaching. You might think its only worth gathering the low tannin White Oaks, as they need less leaching, but Native Americans often preferred the flavor of the Red Oaks.

You shouldn’t feel guilty about destroying all those potential Oak trees. The tree produces far more seeds than it needs to reproduce itself, and at best only one in a thousand has any chance of becoming a new tree. If you do feel bad, you could plant a few of the very best acorns in a suitable spot.

Storage: Prepared acorn meal can be dried and stored, but it tastes much better when fresh, so usually only small amounts were ground and leached at one time. The tannin in the whole acorns helps preserve them and deters insects such as weevils. For storage they were dried in the sun, which also kills them so they don’t germinate. In California they were often stored in granaries on stilts (to deter rodents), often with wood ashes or insect repellant herbs such as Mugwort or Sagebrush.

Preparation: Like their cousins the Chestnuts, acorns have a tough leathery skin, rather than a hard shell. This can be removed from the dried acorns, by cracking them between two rocks. You can also soak them overnight, which causes them to swell, soften and split. Removing the kernels from the shells is a rather tedious job, so it was often given to children and old people. The kernels can be leached whole, but the process is speeded up by first grinding them to meal. The easiest way to do this is with a blender.

Leaching: Though some acorns are sweet without any preparation, most need leaching to remove their tannin. There are a number of ways to do this.

  • The simplest way is to grind the shelled nuts to a coarse powder (easy to do with a coffee grinder, food processor or blender). You then half fill a large jar with the powder, top it up with water and put it in a fridge (or other cool place). The water will gradually leach the tannins from the acorns and turn brown. Carefully pour off the brown water daily and re-fill the jar with fresh water. When all of the tannin is gone (this takes a few days) it is ready to use.
  • A faster method is to boil the acorn meal in water, changing the water every time it turns dark brown. When the water no longer turns brown they are ready. An alternative is to repeatedly dip a bag of acorn meal into clean hot water. A recent innovation is to put the kernels in the blender with hot water and blend. Then drain, squeeze and add more water, repeating as necessary until the water is clear.
  • Another easy method is to put the whole kernels or acorn meal (faster) in a bag and leave it in running water (or under a dripping tap). Squeeze the bag occasionally to hasten leaching and in a few days (the exact number depends on the type of acorns) they should be sweet and palatable.
  • Probably the best way is the simplest is to grind the shelled nuts to a coarse powder (easy to do with a coffee grinder, food processor or blender). You then half fill a large jar with the powder, top it up with water and put it in a fridge (or other cool place). The water will gradually leach the tannins from the acorns and turn yellow. Carefully pour off the brown water daily and re-fill the jar with fresh water. When all of the tannin is gone (this takes a few days) it is ready to use.

Use: Acorn mush, made by boiling the leached meal, was the staple food of many tribes. It swells up considerably with cooking, so that a quart of meal may yield five quarts of mush. They often added berries, ground seeds and nuts for additional flavor.

The prepared meal was also used to thicken soup, make tortillas and to bake bread. They made bread by mixing the meal with water and forming little cakes, which were dried in the sun. It could also be made by baking the dough overnight in a fire pit. Pit baked bread was said to be sweet and dark brown, with excellent flavor and keeping qualities. John Muir often carried acorn bread on his treks and claimed it gave more strength than wheat bread.

The leached whole nuts can be used in breads, cookies, trail mixes, roasted and cereals. The leached meal can be mixed with an equal amount of wheat flour for baking muffins, bread and pancakes.

New crop: Today the oaks are almost totally ignored as a food resource, but they could become important once again. They are probably the most valuable wild food of the northern Temperate Zone. It has been said that the Oaks produce more nuts annually than all other wild and cultivated nut trees combined. It is somewhat strange that we go to exotic distant lands to find Amaranth, Tef, Quinoa and Spirulina, while ignoring such valuable native plants sitting in our back yards. I think acorn flour has the flavor and nutritional value to be a viable commercial food product.  There is a good opportunity for some enterprising individuals to produce acorn flour, breads, muffins, pancake mix and cereals.

Oil: Some tribes apparently extracted oil from the acorns (they contain about 20% fat), by boiling and skimming as for Hickory (See Carya).

Medicine: An astringent decoction of Oak bark has been used as a douche, enema, gargle and to wash smelly feet. It is emetic so is not taken internally.

Native Americans used the mold that grew on old acorn mush to treat wounds and open sores. This sounds a lot like an antibiotic to me.

Tannin: Oak bark has long been an important source of tannin for tanning leather. In Britain this was one of the main products of Oak coppice. The tannin from an acorn food processing plant might be sold for this purpose. It has been said that the acorns with a high tannin content might be preferred by such enterprises, because the leached tannin is a valuable commodity in its own right.

Animal food: Oak trees provide food and shelter for innumerable creatures, from insects to wild turkeys, woodpeckers, jays, rodents, raccoons, peccaries, deer and bears. The acorn crop is an important factor in determining the population levels of many of these animals. Acorns are also valuable feed for livestock and Europeans have allowed cattle and pigs to forage in Oak woods for centuries.

Wood: The Oak genus supplies more hardwood lumber than any other, though the quality of wood varies enormously with the various species. Quite a few species tend to have short trunks and gnarled branches and are useless as lumber.

The White Oak (Q. alba) is one of the best North American hardwoods. It has an unsurpassed combination of toughness, durability, hardness and ease of working and is widely used for cabinetmaking, flooring, veneer, paneling and millwork. In earlier times it was also the first choice for building construction. Unlike most other Oaks, White Oak wood is non‑porous and was prized for whiskey barrels and shipbuilding. It was once commonly used for roof shingles and siding.

Coppice: Oak sprouts readily from the stump and in Europe the trees were once widely coppiced for poles, fenceposts, basket materials, tanbark, charcoal and firewood (for more on coppicing see Hazel ‑ Corylus).

Baskets: White Oak splits were a favorite material for making baskets. Saplings up to six inches in diameter were cut in spring or summer, trimmed to length and then split into strips of the desired width. These strips were split along the growth rings to make thin supple splits, ideal for weaving.

Fuel: The Oaks are the most important firewood trees in North America, as they are excellent fuel, giving from 22‑27 million Btu per cord and are widely available. I mentioned timber rustling under Walnut (Juglans), but most timber rustling is of Oak, cut for firewood. In California even the legal cutting of the slow growing native Oaks is a problem and native Oak woodlands are shrinking rapidly in many areas. Part of the solution to this problem could be Oak fuel wood plantations, as the trees coppice well.

Ink: Oak galls (swellings caused by insect larvae) were used for making ink, notably that used for printing money.

Propagation: Oaks are easily grown from seed. Select ripe acorns from the most suitable parent trees and plant immediately under a mulch, with protection from rodents. Acorns die if they dry out, so keep them moist. You can plant them in containers, for planting out at a later date. The seeds naturally germinate almost as soon as they fall to the ground, their strategy being to use up their food reserves up as quickly as possible and so reduce their attractiveness as a food source. Seedlings are often abundant under Oak trees and these can be transplanted successfully when very young. There are species of Oak for all soil types and growing conditions.

Fertilizer: Chopped Oak leaves (run them over with a power lawnmower to shred them) are invaluable as a soil building  mulch or soil amendment. Sifted leaf mold from the forest is often used in potting soils, or for mulch. Contrary to popular belief Oak leaves don’t acidify the soil very much, though you might want to add lime if your soil is already acid.

New crops: Oaks improve the soil, encourage wildlife and provide timber, fuel, fodder, fertilizer and tannin, as well as an edible crop. Such useful trees could be an important component of a future farm, which relies on a mix of trees, shrubs, herbs and grasses, rather than a single species monoculture. Some of the best food species are adapted to hot arid climates and could be potentially valuable as multi‑purpose crops for third world countries. There are already a number of improved cultivars that bear sweet acorns with a low tannin content (notably of Q. alba and Q. macrocarpa).

Species include:

These trees are divided into two groups, the White Oaks and the Red Oaks. Species in each group may hybridize, in which case it may not be so easy to tell which species you have. Fortunately this doesn’t matter, as any acorns can be eaten if leached properly.

White Oaks:

These species are distinguished by the rounded lobes on their leaves. They take only one year to produce acorns and generally produce the sweetest types. A few species produce acorns that can be eaten without any leaching at all. The best species include:

Q. alba ‑ White Oak        

Q. douglasii ‑ Blue Oak

Q. dumosa ‑ California Scrub Oak  

Q. emoryi ‑ Emory Oak

Q. gambelii ‑ Gambel’s Oak     

Q. prinus ‑ Chestnut Oak      

Q. macrocarpa ‑ Bur Oak

Q. michauxii ‑ Swamp Chestnut Oak

Q. lobata ‑ California White Oak

This big tree can be very productive (one very large tree was observed to yield a ton of acorns) and its large acorns are of high quality. Consequently it was one of the most important Oaks to Native Americans. At least one improved cultivar is available (Ashworth).

Red Oaks

These species can be identified by their pointed leaf lobes. They take two years to form their acorns, and these contain a lot of tannin. Some bitter ones contain so much tannin as to be quite toxic. One benefit of a high tannin content is that they stay wholesome for a longer period. The best species include:

Q. agrifolia ‑ Coast Live Oak

Q. kellogii ‑ California Black Oak 

These are two of the best tasting and most nutritious Acorns and were among the most important species for Native Americans

Q. chrysolepis ‑ Canyon Live Oak  

Q. rubra ‑ Northern red Oak

Q. wislizenii ‑ Interior Live Oak 

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