I have 1.5 acres (about 160 trees) of black walnuts planted 12 to 14 years ago. I grafted them to good nut producing cultivars so they would be a bit easier to shell than wild nuts. Here are a couple of suggestions that would help folks wanting to grow their own.
1. Northern Nut Growers is an excellent resource for info about nut growing.
www.nutgrowing.org/2. The easiest way to harvest walnuts (or pecans!) for home growers is with a nut wizard.
www.nutwizard.com/3. Black Walnuts should be harvested just after they fall from the tree, while the nut is still green. They can be shelled by running over them with a car in the driveway (very very messy!) or by running them through a corn sheller (better, but still messy). Commercial hullers can be made if you are good at shop work by modifying the front wheel assembly from a front wheel drive car with a 3 point hitch for a tractor and running it off the PTO.
4. Using high pressure water is a good way to clean walnuts. You can wash them in a 5 gallon bucket full of water by stirring them with a shovel. This is not very effective, but it does work. When clean, lay them out to dry in trays or on wire screen trays for at least 2 weeks. Test crack a few to see when the moisture is at the right level.
5. Cracking black walnuts is tough. A hammer and stick of hardwood is one way but a bit slow. There are several walnut crackers listed at the NNGA website above. I use a Master nut cracker purchased from Gerald Gardner several years ago. He lists them on Ebay for about $75 under the user name nutty-nuts. He is a great guy with tons of know how about growing walnuts.
6. I personally will not harvest wild walnuts except from a few select trees. They tend to not fill well, have dark nut meats, are difficult to extract, etc. I have found exactly 2 wild trees in north Alabama that are worth collecting nuts. One of those trees can be seen on the north side of the road here.
maps.google.com/?ll=34.160999,-86.488589&spn=0.000587,0.001321&t=h&z=20 The tree is almost exactly dead center of that google map on the north side of the road to the left of the small dirt road.
7. For good producing grafted walnut trees in Tennessee, Alabama, and further south, I suggest Thomas, Neel #1, Pounds #2, and Surprise. For Iowa and other midwestern climates, look for earlier maturing varieties like Mintle, S127, Mcginnis, and Sparrow. There are some varieties that I refuse to grow because of significant cultural problems. Emma K is one such variety. The hull is so tightly stuck to the nut that it is almost impossible to remove. Other named varieties were selected solely because they produce a huge nut or a very pretty kernel. These should be avoided because they produce such a small crop. I would put Ridgeway and Bowser in this group. A good source for grafted trees is Nolin Nursery.
www.nolinnursery.com/ You might also check out their hickory, hican, pecan, and other nut producing trees.
You will find a ton of good information and a nearly equal amount of mis-information about growing black walnuts, particularly with respect to the value of the wood. The trees can be pruned to form a high quality saw or veneer log if you want to do the work involved. Don't expect to get rich, it takes at least 40 years to get a small harvestable tree and up to 75 years to grow a premium veneer log.
A couple of warnings should be included. The juglone the tree produces is highly effective at suppressing competing plants including tomato and potato. Don't use walnut leaves or debris as horse bedding, it can cripple horses. Tea properly made from the husks of walnuts is highly effective at killing abdominal worms. I would not recommend it, but it was a remedy used in years past. And last but not least, Black Walnuts will stain your skin dark brownish black. Wear gloves when harvesting if you want to keep your skin color.
If you want to put your walnuts to good use, make a black walnut cake or some black walnut fudge. The flavor is incredible!
DarJones