Along with a kaleidoscope of changing leaf colors and pumpkins, acorns are a staple of fall across the United States. The strange little nut is actually the fruit of an oak tree and is sometimes referred to as an oaknut. While they can be found in abundance all across the country, they oddly enough play little to no role at all in our diets. That wasn’t always the case, though. Acorns were once a dietary staple in numerous cultures both in the US and around the world.
No doubt you have seen the outside shell of an acorn, which sit inside a woody cup-like base called a “cupule.” Though they can vary slightly in appearance depending on the species of Oak, the cupule is always a distinguishing feature. Oaks don’t begin to bear fruit until they are around 20 years old, and peak production occurs from 50 to 80 years.
Most Oaks only bear fruit once a year and some acorns can require up to 24 months to mature. Like many trees, Oaks have irregular cycles of boom and bust but the why and how of these cycles remain a mystery. Boom times, called “mast-years,” occur every 2-5 years, with few acorns in between. However, mast-year production tends to be highly prolific with a single Oak producing nearly ten thousand acorns in a reproductive season. During a lifetime, that can add up to over 10 million acorns!
When you see squirrels and chipmunks stockpiling food for winter, chances are high that a large portion of those supplies are acorns. But a slew of other animals also depend on the nuts, including deer, bears, raccoons, mice, and a number of other rodents, as well as several species of birds, such as ducks, jays, pigeons, and woodpeckers. In Spain, Portugal and the New Forest region of southern England, pigs are still turned loose in large oak groves called “dehesas” in the autumn to fill and fatten themselves on acorns.
There’s a reason so many animals eat acorns – they are abundant and highly nutritious. Percentages vary according to Oak species, but all acorns contain large amounts of protein, carbohydrates, and fats, as well as calcium, niacin, phosphorus, and potassium. They are also loaded with something called “tannins” which makes them unpleasantly bitter to many animals, including humans. Consuming too much tannin can also make it hard for sensitive digestive systems to get any nutrients out of the other foods they eat, and can even become toxic at highly concentrated levels.
Since tannins, which are plant polyphenols, can interfere with an animal’s ability to metabolize nutrients, the animals that do eat them have adapted in different ways in order to use the acorn’s nutritional value. Oak trees are also dependent on animals. Because acorns are quite heavy, they fall close to the tree. Therefore, Oaks need animals — especially squirrels and jays — to spread these seeds to a desirable place for germination.
Although acorns are rarely featured in our diets today, they served a very important roll in early human history dating back to Paleolithic times. They were a staple food for many cultures which all developed ways to to leach out the tannins, usually by soaking them in water. Another method of removing the tannin would be to bury the shelled acorns in mud for several weeks. Acorn meal was commonly used like flour to make bread everywhere from Europe and the Middle East to Asia and the Americas.
The nuts were particularly important for many Native Americans living in California where Oak trees were an abundant and reliable resource. Funny enough, the processing required to remove the tannins was considered such arduous work that the Cahuilla people of Southern California believed that the bitter nuts were a curse from the Creator. Acorns are still an important part of modern Korean cuisine. Acorn starch is used to make a gelatin called dotori muk, which is used in salads. Acorn flour is used to make noodles called dotori gooksoo. Sources: CSUS, Daves Garden, International Oak Society, Wikipedia)
