Claro Walnut Characteristics
From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Claro walnut is called Juglans californica. It is native to the USA. Common names include California black walnut, California walnut, claro walnut, southern California walnut. I do believe that this is the species you were offered. Claro walnut lumber would most often come from walnut orchard trees, so grain and color can be variable indeed. Note that it is a species all by itself, grown in Western U.S., and produces claro walnut lumber.
Sometimes, claro walnut is grafted to the root stock of English walnut. This might be the source of information on the previous posting. This would be rare in the U.S. Sometimes claro root stock has English walnut grafted to it because the roots are resistant to decay and the top produces tasty sweet walnuts.
From contributor F:
Being out west and having worked extensively with Claro walnut, I can tell you that English walnut is often grafted on to claro root stock and I have never seen the opposite. The reason for the grafting is that the claro root is heartier in this climate and soil and the English nuts are preferred because the shell is thinner and the yield of nut meat is much higher than from the black/claro which have thick shells and smaller nut meats. Although the trees the stock comes from are most often orchard trees, the trees grow rather large and the lumber is available in very long lengths and many thicknesses. Other than that, I can only say that this wood is beautiful and often figured when from a large tree. A real pleasure to work with. The English is different entirely and very pale in comparison.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor S:
Today, however, many refer to all western walnut as Claro to differentiate from its eastern cousin Juglans Nigra (which is a commodity hardwood and the western species is not, which means a big money difference). It is my understanding that the root stock used in orchards is a native walnut species Juglans Hansii. English walnut has a tendency to rot so using the native species adds life of the tree.
In Oregon, it is not uncommon to find Juglans Hansii in whole tree form. It is apparent by its small, round, quarter sized, thick shelled nut (also stated above). They typically do grow to be large trees but I suspect that some of the difference between it and the eastern species has a lot to do with environment. I say that because there are occasions when we have harvested an eastern walnut tree and the lumber turns out with less color variation but still beautiful colorful wood. The Claro color has to do with the species but in my opinion it also has much to do with how it is dried. The entire process of harvesting and drying is different making western walnut lumber a unique and independent product from eastern walnut. We air dry our lumber one season (summer to summer) per inch. After that we can use our dehumidifying kiln to extract moisture getting the wood down to 6-8%. It is most common to find eastern walnut dried in a steam kiln. Steaming bleeds the tannins from the heartwood into the sapwood, which allows a higher grade of lumber.
Many believe that Claro is a California species but we have seen many Juglans Hansii as far north as British Columbia. Harvesting Claro logs allows us to cut lumber in standard lengths (6’, 8’, 10’ and sometimes 12’). It is not usual for the butt cut to yield a log over 20 feet long.
In the Pacific NW walnut trees often stand alone either in a field, yard, along roads or in a parking lot. Point is they have room to grow and in very good soil and climate conditions. In the east, however, while you do get the occasional stand alone tree, most are harvested from a forest. In a forest, trees grow up rather than out.
Comment from contributor A:
We have been harvesting and selling western walnut for 33 years here in Oregon. I think the correct description of our walnut is that it is a hybrid of Juglans Nigra and Juglans Hindsii. It is similar in color and figure to the "California Claro" but is denser with the strength characteristics of American black walnut. Most of the trees we see are not orchard graft stock and are from 24" to 72" in diameter with useful logs up to 25' long.
A typical mill log would be 36" in diameter and 12' long. We air dry 1" per year and use a DH kiln to complete the process and take lumber down to 6% - 8% moisture content. Western walnut typically sells for a 30% to 50% premium over American black walnut.
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