Oak trees are critical infrastructure in the warmer, drier parts of our region, often associating themselves with pines, hickories, and many of our most prized mushroom varieties. They may seem fairly abundant in some places, but in others, they are lone merchants, providing a small, but critical supply of acorns to local deer. In some of the places I hunt in northern New England, I can walk a mile or more before coming across a stand of oaks, and often those stands consist of only a handful of trees. Knowing that deer rely on these small patches, I won’t harvest any acorns from them. Instead, I’ll wait until I’m in a forest where oaks are plentiful, and even then I’ll make sure to leave more than two thirds from any tree for the local wildlife and the oaks’ reproductive strategies. I’ll harvest the most during mast years when oaks dump many more acorns than they usually do. Haines (2011) doesn’t list any of our regional species as having a conservation status, but be courteous of local wildlife needs and general forest diversity.
- Acorns after processing (see Process section below)
- I don’t recommend using any other part of an oak tree, but Couplan (1998) mentions some other historical uses including ash for baking powder and leaves for external medical applications
Oaks are usually deciduous, especially in northern climates (Little, 1980). Like most trees, the easiest way to identify oaks is by their leaf, which is uniquely shaped. The leaves appear alternate on the stem, meaning that they are not directly across from in each other in symmetrical pairs. They are usually deeply lobed (see picture), meaning that the edge of the leaf moves in and out dramatically. The twigs of oaks have star-shaped pith (Little, 1980). Leaf edges can appear jagged or smooth, depending on the individual species.
The acorns, or seeds of the tree, are attached to the tree via a cup on the flatter side of the acorn (the other side is usually a sharp point).
Like the leaves, the acorns come in all different shapes and sizes, depending the species, but are generally between an inch and three inches long.
The two main groups of oaks in North America are white and red (Brockman, 2001). The red oaks are also sometimes referred to as black oaks (Gibbons, 1964). Although the acorns of both groups are bitter if not treated properly, the white oaks are generally less bitter (Brockman, 2001; Thayer, 2010). This does not seem to be because of a notable difference in tannin levels. In fact, Thayer (2010) shows a break-down of the tannin levels in many major species from both groups and the high and low ranges are considerable and overlap between the groups. Perhaps the easiest identifying feature separating the groups is that white oaks have more rounded, smoother edges, whereas red oaks have pointed edges, otherwise known as “bristle-tips” in the tree literature (Petrides, 1958). (Brockman, 2001). Red oaks take two years for the acorn to fully mature, often resulting in two different sized acorns on the same tree, while white oaks only take one year (Petrides, 1958). The shells of white oak are not hairy inside like they are in red oaks (Brockman, 2001; Petrides, 1958; Thayer, 2010).
Among the white oaks common in the northeast are standard white oak, Q. alba, bur oak, Q. macrocarpa, post oak, Q. stellata, chestnut oak, Q. prinus, swamp white oak, Q. bicolor, chinkapin oak, and Q. muehlenbergii. The red oaks include northern red oak, Q. rubra, black oak, Q. velutina, scarlet oak, Q. coccinea, pin oak, Q. palustris, and bear oak, Q. ilicifolia. I have not eaten all of these varieties, but Oaks are widespread throughout the northeast. They tend to be most prevalent in drier soil, in slightly warmer areas, at lower elevations and generally more moderate weather conditions than many other deciduous species in the area. In fact, climate migration studies suggest the north east will see a marked increase in oak forest types over the abundance of maple, beech, and birch forests as those species begin to move further north (Tang and Beckage 2010; Iverson et al. 2008; Treyger & Nowak, 2011).
Poisonous look-alikes for oak trees include poison oak, Toxicodendron pubescens, which has leaves which somewhat resemble oak trees. The two aren’t related to each other as oaks are part of the beech family and poison oak is a member of the cashew family. Since I don’t recommend eating the leaves of oak and since poison oak doesn’t produce an acorn, the only danger in confusing them is if you find yourself brushing up against poison oak leaves when searching for acorns. Given that poison oak sometimes shares the same dry habitat of oak trees, there is a possibility of this happening if you aren’t careful (Turner & von Aderkas, 2009). The leaves can create a rash similar to poison ivy if they are touched. Luckily, they take the form of vines and woody shrubs, so they would only be confused with small, immature oak trees. Poison oak appears shinier and has clusters of three leaves, while oak leaves appear in rows of five (Little, 1980).
Regular poison ivy, Toxicodendron radicans, may also resemble oak leaves as it occasionally produces leaves that have irregular lobes. Poison ivy sometimes grows as a vine, wrapping around nearby trees or shrubs, blending in easily with adjacent oak leaves.
Although Euell Gibbons (1962) and some other authors claim to have eaten raw or roasted acorns without leaching them of tannins; I don’t recommend this. I’ve eaten a very small amount raw and found them intolerable. Moreover, tannins are toxic to humans. According to Turner & von Aderkas (2009), eating enough tannins may cause inflammation, irritation, and even hemorrhaging of the walls of one’s intestines and can hurt the liver and kidneys. Turner & von Aderkas also claim that the young shoots and leaves of some species are poisonous, but they don’t specify which ones.
Acorns can be harvested between August and November whenever they are ready. I follow the tip that if the caps detach easily from the acorn, they are ripe (Thayer, 2010). They can either be removed from the tree or picked off the ground, though bear in mind that a higher proportion of the ones on the ground will be rotten or grub infested unless there was a recent storm. There is a whole science behind finding acorns that are not rotten and with enough practice, foragers can become adept at picking out the good ones. Thayer (2010) has the best overview of this science. Strategies include examining the top of the acorn, or flatter area for small holes, discoloration, or an uneven disk (meaning it looks like part of it has fallen inward or is being pushed out). You can also look for dark streaks or splotches on the sides of the acorn. All of these characteristics are indicative of a rotten or grub infested nut. Finally, you can squeeze the acorn or tap it against something hard to see if it appears firm or mushy on the inside. The mushy or soft ones are definitely rotten.
After visual inspection, I always check for rotten ones by filling a pot with water and then dropping in handfuls at a time. Acorns that float are probably bad. This test is not full proof and I often still find rotten ones that sink and sometimes good ones that float.
Acorns from most oaks (Quercus) can be eaten, though some are much better than others, and all have to be processed to remove their tannins. Sorting and processing acorns is not for the faint of heart. It requires a lot of patience and a lot of energy, not just human energy but energy from natural resources as well. In Nature’s Garden, author Samuel Thayer dedicates 50 pages to identifying, harvesting, processing, and cooking acorns. I strongly recommend purchasing this book to learn the techniques. No other books or websites I’m aware of cover the topic as well as Thayer does.
My preferred method is one of several cold water leaching techniques. I prefer this particular method because I live in a small apartment without access to a woodstove and I want to use as little energy as possible for sustainability reasons.
After weeding out as many bad acorns as I can (see above in Harvest), I spread them on a baking sheet or other flat surface until I’m ready to crack them (but no more than a couple days). Without proper conditions for drying, the nuts will go rancid rather quickly.
Then I run them through my Davebuilt Nutcracker (which is one of the only nutcrackers on the market that can crack acorns efficiently).
Without access to a nutcracker like this, you can use Thayer’s (2010) towel method or my pizza box method (I recommend Thayer’s towel method over the pizza box method). The pizza box method involves placing the nuts in a pizza box, closing the top and smashing them with a hammer against a hard surface, like a stone walkway, driveway, or barn floor (some surface that you don’t mind scuffing up and denting). I also use this method for butternuts and black walnuts in a pinch. The box will prevent the nut shells and meat from flying everywhere at least until the box begins to degrade, which doesn’t take long. Whenever you smash nuts with a hammer, I would recommend wearing safety glasses because it’s really easy to get hit in the eye by sharp pieces of shell. After the nuts are cracked, the meat has to be removed from the shell. You can scrape it out with a lobster pick or jackknife. Extreme patience is required, unless you’ve used a nutcracker, because the nutcrackers will separate half the meat for you and the other half will be relatively easy to pick from the shell. Don’t be frustrated when you find that many of the acorns appear to be rotten even if you tried your hardest to separate the rotten ones earlier on in the process.
Next, I try to remove as much of the fuzzy skin as possible from the nut meat. I use a combination of my finger nails and a small paring knife to scrape off the skin. I don’t try too hard to get it all because it will take forever and some of it will work its way out through the leaching process. If you’ve extracted your nut meat by a hammer cracking method, you’ll find that it’s almost impossible to remove this skin because most of your nut pieces are already in small fragments.
Next, I put the nuts in my 8-inch wide mortar and smash them with my heavy duty pestle. They are hard to break because they are a perfect combination of tough, but pliable. I do my best to get them into small pieces ranging in size from cornmeal to five times bigger than corn meal (the smaller the better).
I then put the pieces into a jar and cover them with water, put a top on them and put them in the fridge.
Every day for the next 6-7 days I decant the water off the top of the jar (which includes some of the fuzzy skin and more importantly, the tannins). You can see in this image how the water on top is brown with tannins.
Then I pour fresh water in the jar, stir it and let it sit another day before repeating. When the fresh water is first poured in, it will look more like the jars on the left. After given a chance to settle fully, it will look more like the jar on the right.
I prefer this cold water leaching method to the heating methods because my fridge is running regardless of the acorns, so I might as well take advantage of the energy being expended rather than run my stove-top for the hours upon hours it takes to leach them by boiling. Moreover, there is some energy efficiency benefits to retaining cold in your fridge through the thermal mass present in jars of water. This is also a very passive exercise that only takes three minutes a day to carry out, making it the easiest method in my opinion.
At the end of the leaching process, I decant the water one last time and then dump the acorn meal into a jelly bag or cheesecloth to strain it of water. The jelly bag technique featured below is much easier and less messy.
But, in a pinch, cheesecloth will work fine if you double or triple the layers and secure it to the rim of the jar with an elastic or hair band, as shown below.
Squeeze the meal in a ball surrounded by the cloth and it almost instantly loses most of its water. Then you can take this ball of damp acorn flour and add it to any recipe requiring flour. If the particles don’t look small enough to you, you can always throw it in a blender with some water and pulse it a few times. This tends to work pretty well to get it as small as possible.
Just remember that it doesn’t rise like normal flour, so it’s best to mix it with real flour in whatever recipe you’re using. A 50% mixture does fairly well for pancakes. Cookies and brownies are much more sensitive and need to be less than 20%, unless you want to experiment with changing the other ingredients in the recipe. I should emphasize that cookies and brownies are a real trick, but worth the effort if you can master it. Don’t give up if your first attempt at making them is a disaster. You’ll have to experiment with small batches until you get one that works. I’ve also used the flour to make fudge with great success. I recommend treating the acorn like you would nuts in a nut-fudge recipe rather than treating it as a core ingredient that goes in earlier in the process. You’ll find that the acorn has a strong flavor and color even when used in small quantities. It is absolutely delicious!