Growing & Processing Black Walnuts


Jump to:  || Squirrels || Cleaning || Extraction ||
I have two black walnut trees (Juglans nigra) and two Carpathian walnut trees. Note that English, Persian, and Carpathian, all refer to the same tree (Juglans regia.)  There are more than 400 cultivars of black walnuts. While the cultivar 'Thomas' is not suited to my midwest locale because of its susceptibility to anthracnose, it does produce very large nuts.

To select the cultivar that is anthracnose resistant, produces a very large size nut, and has a history of success in your area, it will be necessary to talk to your County Cooperative Extension Agent and the nursery you plan to purchase from.  It would be silly to save $20 at the time of purchase, only to find that the tree is unsuitable when it is old enough to bear.  If you do contemplate the purchase of any nut tree or already own nut trees, I recommend "Nut Tree Culture in North America" published by The Northern Nut Growers Association, Inc., 1979, ISBN: 0-9602248-0-7  for the best background information. Some of the information in this article was drawn from that fine book.  While I do lampoon some of the outdated advice on cleaning the nuts and extracting the nutmeats found in that book, it remains an important one in my library.

Walnut trees are attacked by some 64 diseases and 296 species of insects and mites.  I have used a fungicide in the spring as the leaves emerge, but usually just let nature take its course.  Lacewings take care of the aphids; new growth containing colonies of walnut caterpillars can be cut off for disposal; and the larvae of the walnut husk fly cause no serious damage and are destroyed during husk removal.  Walnut pests in your area may be less or more significant.

Walnut trees suffer for want of nutrients in competition with grasses and weeds.  I do add fertilizer every 2nd or 3rd year at a depth of about 8 inches around the drip line.  In addition, walnuts benefit from trace quantities of zinc.  If your soil is deficient in zinc, there are two easy remedies which can be applied on the same schedule.  One is the application of zinc sulfate (sold by Stark's), and the other is Acecap zinc implants (not in Leonard's catalog anymore, but may be available to special order).  I tried the implants one year (4 per tree), and the nut production was phenomenal.  I don't think that I ever want that many nuts again in the same year.

Nut production across the various cultivars is a bit of a mystery.  Some trees bear a few nuts every year with a major flush of nuts every third or fourth year.  Others bear only every 2nd or 3rd year. I apply fertilizer in early spring in the year in which I guess that the tree is due for heavy production. Guessing wrong about the year in which to add fertilizer does not appear to create any problem.

Harvesting Nuts:

To have nuts to harvest in the bearing years, it is necessary to know something about squirrels. Recreational gardeners with one or more trees cannot avoid a certain amount of pilferage.  Some of the methods used in commercial walnut groves simply cannot be applied in urban areas.  Tall straight trunked trees isolated from nearby jumping off points on other trees can be protected by sheet metal bands around the trunk during August and September.  Killing squirrels is fruitless because they are a part of large breeding colonies covering huge areas.  Replacement squirrels fill empty territories in a matter of days, and the population remains constant despite your best efforts; don't bother. My best defense lies in the proximity of my Carpathian walnut trees.  Their prolific annual production keeps the bushy tailed rats busy, and they prefer the less highly flavored nut.  In many cases, I have observed squirrels eating the husk in preference to the nut, early in the season. Needless to say, after losing 10 to 20 nuts per day on these trees, there are none to few left for me at harvest time.  My greatest harvest from the two Carpathian trees was 800 nuts, but that was the year in which I used the zinc implants.  The squirrels were simply overwhelmed with nuts, and therein lies the best defensive strategy, i.e. provide alternative sources of forage, especially those which ripen just before and during the period in which your nuts are ripening, or simply overwhelm the critters with more nuts than they can eat and bury.  Based on the number of Oak seedlings I find every spring, there must be a number of trees somewhere in the neighborhood.  Maturity of the acorns probably coincides with that of the Black walnuts.  Therefore, I have begun planting Oak trees.  As they begin to bear mature acorns, the squirrels will have had their fill of Carpathian walnuts prior to ripening and leave my black walnuts alone during final ripening, in preference to acorns. A less peaceful view of squirrels may be found at:  http://www.deadsquirrel.com/index.html

Harvesting nuts is not like picking apples.  Do not pick nuts from your trees as there will be too much damage to bearing branches which will slow future nut production, and you will have to wait for the husks to soften anyway. In September, check the ground underneath your trees regularly for dropped nuts.  Collect those. By September 20th in the Chicago area, the nuts are ready to be shaken out of the trees. I use a plastic coated hook on a two piece aluminum tube about 17 feet long.  Shaking the branches (up and down rather than sideways) usually dislodges a rain of heavy nuts.  I would wear some form of head protection but they seem to just glance off the sharply pointed ridge that I call my brain- case.  Do not try to dislodge each and every nut.  The effort is not worth it, and you may begin to break some of the weaker branches.  Check the ground  three or four times every day thereafter, especially when there is a strong wind,  and pick up the balance of the nuts during the following two to three weeks.

Cleaning Nuts:

"Numerous methods have been used to remove hulls.  Where only a few bushels of nuts are involved, they can be tramped off, placing the nut with husk on a hard surface and rolling it under a heavy foot.  Light hammer blows will remove the husk; the nut can even be hammered through a hole in a piece of wood forcing the hull off. Nuts can also be driven over with an automobile to crush the soft hulls.  The use of a small trough-shaped box under a jacked-up automobile wheel is satisfactory for small quantities.  As the nuts are forced between the turning wheel and stationary trough, the husks are rubbed off. An open box or bangboard at the back of the car will catch the nuts." (1)

I don't use any of those methods, and I consider them quite hilarious, to put it kindly.  But then, I am dealing with a very large nut by comparison with many of the other cultivars.  My method requires the following tools:  a lightweight pair of plastic gloves rated for solvents (such as the Edmont Solvex glove), a jackknife with a 3 1/2" blade, a vise fixed to a workbench, a trash container for the hulls, and a 5 gallon bucket half-full of water. As with most other aspects of life, timing is everything.  Husks which don't dent easily with a thumbnail are too hard to process by this method, and should be set aside for a few more days to soften.

The first procedure I describe is much too dangerous to recommend to most people, so I will follow that with an safer alternate.  

This is what I do, and to be safe, it must be done in the absence of distractions such as telephones and other people:  First, clamp the knife horizontally in the vise so that the blade edge is on top. (Do not attempt this yourself if you do not keep your mind in the same place as your brain.) Score through the husk to the shell by rolling the nut from the front of the knife blade to the end.  This is to be done in the widest portion of the nut at a point halfway between the ends of the nut. Once the husk has been cut through, the two halves can be rotated since they are loose about the shell. Just turn them off, and drop them into the trash, while dropping the nut into the bucket.  You should be able to strip the husks off at least 5 nuts per minute.  Nothing gets stained with walnut juice except your gloves and the knife blade.  Do not be turned off by the presence of husk fly maggots.  They do not harm the nutmeat, and drown immediately when landing in the bucket.

I prefer to process 200 nuts every day until finished.  It takes 35 minutes to remove the husks, 15 minutes to scrub and rinse the nuts two times (and clean the driveway), 2 hours to dry in the sun, 24 to 36 hours to dry internally in my herb drier, and about 4 weeks for the nutmeats to cure.  This is not a big deal, even if your procedures require more time.

Here is an alternate procedure to use when more than one person is involved or when absolute safety is paramount: First, dispense with the vise. With the knife in one hand, cut through the husk by rolling the nut on a newpaper covered hard surface.  Then, you have to drop the knife in order to turn off the husk halves.  It is the same procedure, but much slower because of the extra step, and your knife may get messy.  The problem with my preferred method is the potential for injury as you run some part of your body onto the fixed blade during distractions. There is some evidence that bloodshed will interfere with your ability to garden.

When finished removing husks for that day, take the knife out of the vise first. Rinse your gloves in the bucket with the nuts.  Remove the gloves.  Wipe off the knife blade.  I made a paint type stirrer from 3/8" threaded rod and a flat plate fixed to one end.  The plate has been twisted to increase stirring action.  Insert the stirrer in an electric drill with 3/8 or 1/2 inch chuck,  and agitate the nuts until all of the remnants of hull matter have been removed.  Or, you can find an old broom handle, and agitate the nuts in the bucket by stirring vigorously.  "Remove and discard any nuts that float for those have not filled out well."  That is another old wives tale that I do not believe.  Only about one out of four floaters are not well formed. Pour off the water in the street gutter.  Fill the bucket to the same level and repeat the agitation in order to clean the nuts of any excess husk debris. Do it again for a third or even a fourth time if necessary.  Do not pour off the water onto any portion of your land, as any earthworms under the runoff area will be killed at once.  For the same reason, do not attempt to compost the husks, although there will be no juglone left when fully composted.  See the note on toxicity.

Air dry the nuts on a screen in the sun for several hours.  Northern gardeners should then put the nuts into an unlit gas oven on cookie sheets for 24 to 48 hours in order to dry the nuts inside and out and prevent any mold that might form inside the nuts while they are being cured. The pilot light will usually keep gas ovens at about 110ºF, which is perfect for drying most things except fruit leathers. I prefer to use my herb dryer because excess moisture is carried off much more efficiently.  To cure the nutmeats, place the nuts in an onion sack or mesh bag, and hang up in a ventilated indoor area for 4 to 6 weeks. The nutmeats should be extracted immediately after curing.  If that is not possible, the nuts can be stored in air-tight gallon jars.  Southern gardeners may have enough sun and warmth to eliminate excess moisture levels out of doors.

In the early years, I used to further clean the nuts under a wire wheel.  But I have since found that vigorous stirring in the rinse water with the drill and paint stirrer method eliminates almost all of the husk materials, and that subsequent cracking and extraction processes are not messy.

Extracting the nutmeats:

"Walnuts should be placed in hot tap water and let stand for 24 hours.  Drain off the water and replace with hot water.  After a minute drain off water and let surface of nuts dry. When cracked the kernels will not shatter because they have picked up enough moisture to be somewhat flexible. The extracted kernels should be spread out to dry overnight." (1)

That is ridiculous.  Most solid metals are more flexible than black walnut shells. This type of pre-conditioning is unnecessary if you have a good vise.

"There are many types of nut crackers.  The universal nut cracker owned by everyone is the hammer and anvil (the anvil often being a block of hard wood, the flat surface of a vise, or a rock.)" (1)

I consider that procedure to be unsafe; it is wasteful of your time picking up the scattered projectiles.  In addition, many good nutmeats will be crushed into uselessness because this method can only be applied to the side of the nut.  This is archaic, if not actually barbaric, and does not really produce food, in my opinion.

Here is my method: while holding the widest part of the nut between middle finger and thumb, place the the nut (end-to-end) between the near end of the vise jaws  Note that I do not plan to crack the shell at the sides. Place the thumb above the nut and four fingers below the nut.  Apply pressure until the shell only just breaks, then put the shells into another container. I prefer to catch all the parts and pieces in the hand which is under the nut, but the process would not harmed by letting everything fall into a container under the vise. However, unless your thumb covers the top of the nut as well during the cracking process, pieces will fly everywhere, and there will be nutmeat losses too.  Using this method, you should be able to crack 100 nuts in eight minutes.  Compare that to the time involved in using any of the heavy duty commercially available nut crackers, and you will see that the vise is the only way to do the job. One needs only to have a vise large enough and I suggest that a 4" vise be regarded as the minimum acceptable size. With a 3" vise, or smaller, there would be no way to get your hand under the nut while cracking the shell.

After cracking, 25% of the nutmeats are completely free of the shell of small nuts, but only about 5% with the largest nuts.  That is because larger nuts have expanded lobes at each end of the quarters, and the nutmeats are not easily freed by exposing only one end of the chamber. Extracting the balance from the shells is easy, but time consuming.

I never pick or force out the nutmeats as that leads to too many massacres and mutilations.  I prefer whole pieces.  The openings in black walnut shells are too small to make picking and prying feasible.  I use electrician's diagonal wire cutters to cut the shell at the strategic point which releases the nutmeats in whole solid pieces into my hand (see note below). Half of the shells require but one strategic cut, and others perhaps two or three.  After the first ten minutes, you will discover that certain kinds of cuts never work.  All of the shells are constructed similarly but when cracked open, they break differently.  For each piece of shell, you will soon learn that there is exactly one cut which should always be performed first.  Half of the time, that first cut is sufficient to release the nutmeats intact.  When second or third cuts are needed, you will soon learn where they are to be made for each type of shell piece.  Most of your cuts will be to the outer portion of the shell from the blunt end of the nut.  Don't waste any time at the pointed end of the nut.   Small nuts are very easy to work with as the nutmeats practically fall out when one end of the chamber is exposed.  Larger nuts require quite a bit more work because of the odd lobe shapes. Because of my arthritic hands, I can extract only about 50 large nuts per day, but I can do 100 of the small ones, as they are so easy. I have mostly large walnuts, so it is a struggle to finish by Christmas.

Note:  I have recently switched to the use of a wire cutter made by the SevenStrand Company.  It is a heavy duty instrument, some 9 1/2 inches long with rubber grips, and capable of applying more pressure than standard wire cutters. The SevenStrand Company manufactures fishing wire and compression sleeves, so this tool is easily special ordered from your local fishing tackle shop. I find it much easier on the hands. This device is also available from American Fishing Wire,
1-800-824-9473, but they sell only to dealers.  The stock number of the 8 1/2" version is TPCRP8.5 at $18.27, and the 9 1/2" version is TPCRP9.5 at $24.99.

As the nutmeats are released, toss them into a container which is at least two feet away from you so that little bits of shell and shell powder clinging to your hand are either too light weight or too heavy weight to follow the same path, and both end up in the discard bin immediately below.  No one likes to find bits of walnut shell in food. I like to vibrate the nutmeats on a screen to be sure to eliminate small debris prior to storage.  And, while on the #8 screen, I check them very carefully to make sure that no bits of shell remain (#8 means eight squares to the inch in every direction.) This step is very important because I find at least one small bit of shell in every batch, despite my best efforts.

Nutmeats that are to be used in the next few months can be stored in plastic bags or mason jars. The nutmeats from 250 small nuts will easily fill a quart mason jar, whereas those from 150 large nuts may not easily fit into the same jar.  Long term storage requires freezing of the nutmeats to prevent rancidity  --  remember they are filled with oil.  

The methods described above have been employed by me for processing as many as 2,000 nuts per season.  Above that amount, the use of mechanical equipment (or a larger family) might be preferable, though I am not aware of any commercial processor of black walnuts.  

The flavor of black walnuts is about five times stronger than that of the carpathian walnut meats you purchase at the supermarket.  One teaspoonful of these nutmeats can usually flavor an entire cake  --  at first.  As you get addicted to the flavor, you will begin putting them into cookies, then salads, and desserts.  I once found a recipe for champagne and black walnut salad dressing, and it was delicious. Call the Nursery, you are going to need more trees.

Footnotes:  In the year 2001, I harvested 2660 nuts from one tree.  That quantity put all of my procedures to the extreme test, successfully, and I must say that I have no wish to explore other methods.  For those who find the use of a vice a bit tricky, check out the Crackerjack Nutcracker http://www.nutsncorks.com/ from England. They are not responding to inquiries or orders from the USA (last checked in 2002).

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I read somewhere that a full sized black walnut tree close to your house will attract lightning away from your house better than any other type of tree.  

For a list of plants which will grow under black walnut trees follow this link.