While percent kernel is important, the most important trait of all is total kernel produced per acre expressed in whatever ratio you choose such as pounds/acre or kilograms/hectare or pounds per square inch of tree trunk area. The problem with black walnut is that no variety to date has produced enough pounds/acre to be profitable for commercial production. With that said, the most consistently productive walnuts for me are Thomas, Neel #1, and Football meaning they produce the most pounds of kernel per acre on a regular basis. Varieties adapted further north are at an obvious disadvantage in this measure due to season length and temperature. Cranz nut size is small but the tree makes a lot of nuts and makes them just about every year. It is still less pounds of kernel per acre than the others. Cranz will mature nuts in Iowa and similar far northern climates where Thomas and Neel #1 would fail. Bowser is an example of a superb nut but the tree makes so few of them it is not worth growing.
Taste changes from year to year, but overall, Thomas wins for taste almost every time. McGinnis has an unusual flavor that is really good if harvested and cleaned promptly. The nuts I sent were not harvested promptly. I was not able to harvest until nearly a month after they fell from the trees. When black walnut stays in the husk too long, the nutmeat darkens and flavor suffers. Neel #1 is especially liable to darken under these conditions. If they had been promptly harvested and cleaned, Neel #1 would have been as good or slightly better than Thomas. This brings a critical trait into focus. Shell density determines how easily the husk pigments can penetrate to the kernel. Thomas is obviously denser than Neel #1. Put this down under the overall trait of kernel quality which can be affected by many other things such as leaf density and disease resistance of the tree.
Crackability is obviously important. Neel #1 and Thomas both fall short on this measure. I would love to have a walnut that cracks as easily as a pecan. The cracking and shelling process could be much simpler. It is worth noting that the method used determines how easy a walnut is to crack. I watched Wilbur Donoho crack some Stoker walnuts at the Kentucky Nut Growers meeting in 2005. He used the spur on one of Fred Blankenship’s crackers to split the nut in half on the suture line, then put each half in a specific position in the jaws of the cracker and popped the end off of the nut. Using this method, he got 100% perfect quarters. I might add that Stoker cracks the prettiest kernels I’ve ever seen in a walnut. It obviously does not darken the pellicle of the nutmeat like other black walnuts.
Some nuts fall free of the husk very easily where others are so firmly attached it is nearly impossible to get a clean nut. Thomas is one of the best I’ve seen with Emma K as the worst. You will find this mentioned in some of Bill Reid’s articles. In my opinion, this is not as important as other traits but should be considered in breeding efforts with black walnut. A high pressure water spray system can remove even the most recalcitrant husk. This trait is more important if low tech methods of husk removal are used. It rolls up under the trait of ease of harvest. I washed the Thomas and Neel #1 walnuts in a 5 gallon bucket using a shovel to stir. This does a fairly good job cleaning these two varieties. Farrington and Cranz were not washed.
Some nuts tend to shrivel as they dry. Football makes so many nuts some may not be filled very well so the kernel shrivels. This can be important to crackability since a shriveled kernel is loose and more easily removed from the shell.
Number of unfilled nuts is important. Surprise is a pretty good walnut overall, but it tends to produce about 10% pops. Thomas is at the other extreme almost never producing pops. Neel #1 is in the middle typically producing 2 or 3 percent pops in a given year. Tree care is important to this trait. Fertilizer applied during growth reduces the number of pops. Wider tree spacing has a similar effect.
- How much does a variety produce in kernel pounds/acre?
- How good does the kernel look and taste?
- How easy is it to crack
- How easy is it to harvest and husk?
- What percent kernel to shell ratio?
- How good is disease and pest resistance of the tree?
- What percent pops does it produce?