I love fidgeting — it helps me concentrate while I work, while I read. My favorite way to fidget is to pick at things: old stickers, layers of cardboard, paper wrappers. While I’m out and about, I like to fidget with acorns.

I pick acorns off trees, ideally with the cap on. Sometimes I find acorns on the ground, still intact, reminding me of when I used to collect dozens of chestnuts every fall as a kid. When I find an acorn, I take off the cap of the acorn first, pick through the thick outer layer, then peel the covering of the acorn “meat,” which easily splits into three parts with an entirely different, softer texture. 

I pick acorns off trees, ideally with the cap on. Sometimes I find acorns on the ground, still intact, reminding me of when I used to collect dozens of chestnuts every fall as a kid.

I must have dissected hundreds of acorns this way, but it wasn’t until I was gifted a bag of incredibly sizable — and I mean huge — acorns that I started asking myself if I have a problem. But whether or not I have an obsession with acorns is not really the question I want to write about here. 

Instead, I want to write about some of my unresolved questions about acorns. What are these different parts of the acorn that I’ve been picking apart? What are they called and what function do they serve? To answer these bigger questions, I must first start with a simpler question: Where do acorns come from? Do they come from oaks? Acorns are, after all, the “oaknut.” Or do oaks come from acorns?

Oaks are trees belonging to the genus Quercus whose native range covers a lot of ground: most of North America (not you, Northern Canada), all of Europe, parts of North Africa, all of Southern Asia and Asia’s Pacific Coast. Oaks are often a keystone species, meaning that they have an outsized impact on their environment.

Oaks are often a keystone species, meaning that they have an outsized impact on their environment.

Looking at the wide range of oaks, both spatially and with regards to environment, it makes sense that this genus is huge. The Royal Botanical Gardens website lists well over 400 accepted species, from Quercus acatenangensis to Quercus yongchunana. 

Of these species, 10 oak species are considered native to California, including Oregon Oaks, Coast Oaks, Canyon Oaks and the Island Oak which only grows on the Channel Islands. The oak family includes shrubs in addition to trees. 

California is basically littered with native oaks — I should know, I lived in Thousand Oaks for ten years. Oaks cover around a third of California’s forest acreage, and tend to dominate the environments they inhabit. The oak is also the national tree of the United States, Germany, France and Poland. Oaks are also the symbol of the city of Oakland, where oaks can be seen on the street signs. 

Oaks are mast-producing trees — mast is the fruit (the ripened ovaries of a seed-bearing plant, which contain the seeds) of woody forest trees, which brings us back to the beginning of this article: Acorns! Acorns are a type of hard mast, meaning they have a hard outer shell. 

Acorns tend to grow in bursts. Some years, very few grow. Other years, they grow in abundance. These are called “mast years” because oak trees produce tons of mast.

This way, more nuts tend to get buried, and they get buried further away — which is needed for the oaks to disperse. Many animals depend on these seeds for nutrition, so if a lot of acorns and other seeds are produced at once, more are likely to survive as their hungry predators get full. Full squirrels tend to bury acorns, not eat them.

Many animals depend on these seeds for nutrition, so if a lot of acorns and other seeds are produced at once, more are likely to survive as their hungry predators get full. Full squirrels tend to bury acorns, not eat them.

But what makes acorns such an appealing source of food? Acorns are rich in energy — needed to feed the soon-to-grow trees — because they contain high amounts of starch. These starchy reserves, which are encased in the hard, sometimes green or brown outer pericarp of acorns, are called cotyledons. These cotyledons are separated from the pericarp by the thin, papery seed coat. In acorns, the cotyledons are hypogeal, meaning that they only serve as a nutrient reserve, and will not move above ground as cotyledon leaves, which perform photosynthesis for energy. 

The little hat that acorns wear that the tree grabs onto is called a cap or cupula. It is connected to the branch by the stalk. At the very center of the acorn, surrounded by the cotyledon, is the payload: the embryo that will grow into a mighty tree.

Now to the really big question. If you’re asking, like I initially did, if it might be safe to nibble on acorns off the tree — maybe don’t. Acorns contain bitter, and toxic, tannins, also called tannic acids. Tannins tend to decrease efficiency in the conversion of nutrients to substances usable in the body. They have also been associated with cancers such as esophageal cancer. 

Acorns can even be poisonous for animals. Some animals habitually eat acorns raw and might over consume them during mast years. Overconsumption of tannic acid can lead to renal failure. Interestingly, some tannin associated compounds can be beneficial, and they have antimicrobial properties. Here, the dose once again makes the poison. 

Despite their toxicity when raw, acorns were a staple food for many California Indigenous people, including the Chumash people, whose ancestral lands include Thousand Oaks. The Chumash word for acorn is misi. Misi was collected in the fall and stored throughout the year. To prepare them for eating, the acorns are shelled, dried and then ground into a meal. In order to remove the bitter tannins from the meal, it has to be washed. This can be done by placing a tea cloth in a cone, adding in the meal and pouring water through the meal until it no longer tastes bitter. The final product is acorn flour. Acorn flour was also produced by the Ohlone people in the Bay Area. 

Despite their toxicity when raw, acorns were a staple food for many California Indigenous people, including the Chumash people, whose ancestral lands include Thousand Oaks.

Among other things, this flour can be mixed with water and cooked until it thickens, making Wiiwish, to which flavorings such as bay or mint leaves may be added. However, acorn flour, like other flours, has a pretty neutral taste and can be used in place of wheat flour to make pancakes.

I have been interacting with acorns so consistently in my specific way that it felt like the way I encountered acorns was the only way to see them. But, like all other phenomena in nature, acorns form parts of much larger ecosystems and food systems. My attempt to situate this small piece of nature in its greater context made me appreciate it so much more and I would highly encourage you to do the same. Take a piece of the world that you interact with daily — maybe the bird you see every day on your way to school, or the grass you sit on to eat your daily lunch in the summer — and interrogate it.