How to Eat an Acorn

Oak Harbor's crop of acorns

Cool weather and wind have driven most of the Garry Oak (Quercus garryana) acorns from the  trees. Time to pick them up and make food! I recently went down to Oak Harbor to gather acorns, and in the time since then, the pleasant aroma of drying acorns has inspired me to write a more comprehensive post about our native acorns.

A venerable specimen next to Sauvie Island (Oregon)

Also called Oregon White Oak, Garry Oaks are the only oak tree native to Washington and British Columbia. Oak woodlands and oak savannas are found in lowland valleys, gravely slopes, rocky outcrops, and dry plateaus from southern Vancouver Island southward, through western Washington and Oregon, and down to central California. At the northern end of the their range they are only found below about 2,000 feet, but as you move southward their range extends up to about 4,000 feet above sea level. Garry Oaks begin to mingle with Black Oaks (Quercus kelloggii) and Canyon Live Oaks (Quercus chrysolepis) at the south end of the Willamette Valley, and Blue Oaks (Quercus douglasii) and Valley Oaks (Quercus lobata) in Northern California, and then finally, Coast Live Oaks (Quercus agrifolia) near the Bay Area. You may also find Northern Red Oaks (Quercus rubra), Pin Oaks (Quercus palustris) and English Oaks (Quercus rubor) planted as street trees throughout the Pacific Northwest.

Blocky bark on an old Garry Oak

Garry oaks can reach great proportions when they grow in deep soils that are free from competing Douglas Firs. Of our western oaks, they are second in size only to Valley Oaks and occasionally reach 90 feet in height. However, on dry rocky soils and in areas with little precipitation, they take on a low scrubby form. Most commonly they are between 50 to 60 feet tall and 6 to 24 inches in diameter (See Sudworth’s “Forest Trees of the Pacific Northwest”). Garry Oak branches are often twisted and gnarled and their trunks can sprawl wildly. The mature bark is light grey with deep blocky fissures. Twigs are hairy when young. The leaves are 3.5 to 6.5 inches long, deeply lobed, and are shiny green on top and pale green below with somewhat of a leathery texture. They begin to fall around the end of September but take several months to drop all of their leaves.

The upper (left) and lower (right) surfaces of a Garry Oak leaf

  

Garry Oak acorns mature in one season. Acorns arise in groups of 1-3 and are relatively round, with the widest part at or slightly above the middle of the acorn. They are usually 1-1.25 inches long and 0.625-1 inch wide. Freshly fallen acorns will often still be green, but mature to a reddish brown. Caps are warty and only cover the upper 20% or less of the acorn.

A spectrum of Garry Oak acorn sizes (with a ruler showing cm)

Yikes, this acorn had a wriggly passenger!

The first wave of acorns begins to fall in early September, but these should be ignored by harvesters as they are almost always infected by acorn weevils. Ideally, the ground would then be burned or raked to clear away the diseased acorns in order to disrupt the acorn weevil reproductive cycle and facilitate faster picking when the mature acorns begin to drop. Typically healthy acorns fall from from late September to early November. Burning isn’t usually possible, so acorn harvesters need to know how to distinguish good acorns from bad. Sam Thayer devotes considerable attention to this topic in his book “Nature’s Garden”. To summarize, here are a few things to avoid: (1) acorns that still have caps, (2) acorns with small pin sized weevil exit holes in them, (3) acorns with shells that are separating from the disc at the top (where it attaches to the cap), (4) acorns with damaged vascular bundles in the disc (acorn weevils often enter the acorn through these soft vascular bundles), (5) acorns with dark spots, and (6) acorns that have sprouted but the sprout is dead.

I like to collect acorns with two different sized containers: a 3-4 quart basket that I keep with me (see Blog header photo), and a larger 4-5 gallon sized bucket that I keep in a central location. This allows me to devote more time to picking up acorns, and less time to traveling back and forth to my bucket.

A properly dried acorn (left) and rapidly dried acorn (right)

Once the acorns are collected, it is important to dry them at a slow but deliberate rate. Drying acorns too quickly causes the nutmeat to turn black. While the black color of the heated acorns doesn’t initially cause any problems, my suspicion is that the heat drives the oil to the surface of the nutmeat where it may go rancid more quickly. Additionally, the thin brown covering between the acorn and the shell tends to stick to the acorn when they have been dried too quickly, whereas ordinarily, it sticks to the shell. At the opposite extreme, drying acorns too slowly is also detrimental. This is because acorns contain a lot of moisture when they are still alive. As they acorns begin to dry, they also die. If the remaining moisture lingers too long, the nuts will mold. Some species of acorns in some climates only require occasionally stirring in ambient conditions to dry properly, but our species and humid climate are not so forgiving. Until Garry Oak acorns are completely dry, they should never be left in a bag.

My homemade nut dehydrator

I think the easiest way to dry Garry Oak acorns is to spread them out one layer deep on baking sheets and place them next to a fireplace or forced air heat register. Rotate your trays occasionally and the acorns will dry in a couple weeks. My balanophagous friend Melissa from Oak Harbor recently told me about her success drying acorns in a food dehydrator. If possible, set the temperature of your food dehydrator to a low setting. With a little elbow grease and inexpensive materials you can manufacture your very own nut dehydrator out of a box, some hardware cloth or metal grating, and a small fan. Simply cut a hole in the side of your box near the bottom, suspend the hardware cloth horizontally above the hole, and dump your acorns into the box. The hardware cloth keeps the acorns from interfering with the fan as it forces air through the acorns. I got fancy and riveted together a box from sheet metal and used a partially disassembled thrift store hairdryer for my fan. The hairdryer is nice because I have the ability to blow hot air on the acorns. However, this particular hairdryer is a little too hot and blackens my acorns if left on “hot” for too long. I wish I had used one with variable temperature settings. The hair dryer is also noisy. CAUTION: If you make your own nut dehydrator with a hair dryer, I strongly recommend using fireproof materials and a GFCI outlet to power the hairdryer. It is probably also best to only use a home-made dehydrator in a fire safe area (like a concrete patio).

A Davebilt in action

Once dry the acorns shrink considerably in the shell and have a very hard texture, making them easy to shell. The best tool for shelling acorns is a Davebilt Nutcracker. These run about $150 and can be mail ordered from the small town manufacturer in California. If you are a serious acorn harvester, they are definitely worth every penny. The beauty of a Davebilt is that it operates on a continuous process (rather than a batch process) so you don’t have to stop until you are out of acorns. They work by squeezing the acorn between a wheel and a solid plate. You can adjust the distance between the wheel and the plate to accommodate different sized acorns (or other nuts). I have easily cracked 40 pounds of acorns in an hour! And most of the nutmeats come out as wholes or halves, which makes separating the shells from the nutmeats much easier. Other shelling methods (in ascending order of effectiveness) include the use of your jaws, conventional nutcrackers, and hammers, or better yet, Sam Thayer’s “towel method," which involves using a large piece of wood to crack rows of clustered acorns placed under a towel. Special mention will go to any 2 people that can pitch acorns at each other and get them to crack against each other mid-flight....

Separating the shells from the acorns is a time consuming process. There are many methods to speed up the chore including winnowing, floating, sieving, and shaking, which all rely on the fact that acorn nutmeat is more dense than the shells. Currently, my favorite method is to put the mixture of acorns and shells in a bucket (without water) and shake it back and forth vigorously. The lightweight shells slowly rise to the top and can be scooped off. I then sieve everything through ¼ hardware cloth in order to create two size categories that can be further winnowed and hand-sorted. The fines (which pass through the hardware cloth) are the most tedious to sort. If I have done a good job with the Davebilt, the bulk of the nutmeat will not pass through the sieve and the remaining large shell fragments are easily removed by hand. Though tedious for the eyes and hands, my nose gets a great deal of pleasure from separating acorns. They smell fantastic!

In order to enjoy acorns as food, they must first be leached to eliminate the bitter tannins. Tannins can be removed with hot water, cold water, or chemically (with wood ash, lye, or possibly ammonia). I will write about cold leaching, since that is how I process my acorns. Tannins are water soluble and relatively easy to remove with a little patience. The time it takes to leach tannins with cold water depends on the size of the acorn pieces. The Chinook living on the lower Columbia River buried whole acorns in artesian springs and left them to leach for an entire winter (for more information, read Bethany Mathews fantastic paper on the archaeology of acorn leaching pits on Sauvie Island published in Northwest Anthropologist 2009: Traditional Resources- Terrestrial). Native Americans in California take the opposite approach and pound their acorns into a very fine flour that leaches in less than an hour (albeit a different species). Someday I would like to try and leach whole acorns in an underground spring, but for now, I leach pulverized acorns. I put about 2 cups of acorns into a Vitamix Blender, add another 2 cups of water and then grind them (with earplugs on) for several minutes until I get a fine flour solution. I pour this slurry of acorn flour and water into a gallon sized glass jar, fill it the rest of the way with water, and then put the jar in the refrigerator or outside (if the weather is cool).

Acorn water after the first (left) and fifth (right) day leaching

Over the course of several hours, the acorn flour settles to the bottom and the tannins slowly dissolve into the water. Once a day I decant the tannin laden water (carefully pour it off the top of the settled acorns). Then I add fresh water and stir up the flour, and let it sit for another day. I repeat this process for 3-5 days, until the water nolonger has a reddish brown color and the acorn slurry doesn’t taste bitter. When it is done leaching, I pour off as much water as possible, and then use the product immediately, or store it damp in the refrigerator for up to 10 days.

Frying my Totally Tree Bread

A-Corn Bread ready to be eaten

Once my acorns are leached, I usually make one of two kinds of acorn bread. Totally Tree Bread is made with about 2 cups of wet acorn flour mixed with 1/4 cup maple syrup, spread out on a frying pan with some olive oil. Simply fry it on low heat for 30 minutes, flip it over, and fry it on the other side for another 30 minutes. You can make a savory version without maple syrup and a pinch of salt. Serve with mustard. Currently, my favorite is A-Corn Bread, which is basically a corn bread recipe that substitutes acorns for corn meal. I usually use about half wheat flour and half acorns. However you decide to cook acorns, be aware that the flavor of your dish is primarily determined by the thoroughness with which you have leached your acorns. Garry Oak acorns will always have a hint of bitterness, but properly leached acorns should primarily have a nice nutty flavor with a hint of molasses. Yum! I have some leaching now and I can't wait to eat them!