There are 21 different types of walnut trees in the Juglandaceae family, here are some of the most common
American or Black walnut (Juglans nigra)
English or Persian walnut (Juglans regia)
White walnut or butternut (Juglans cinerea)
California Black Walnut (Juglans californica) - Mostly too small for proper wood
Northern California Black Walnut (Juglans hindsii)
Arizona Black Walnut (Juglans major)
Andean Walnut (also Columbian, Ecuadorian walnut or Cedro negro) (Juglans neotropica)
Japanese Walnut (Juglans ailantifolia)
Little Walnut (Juglans microcarpa) - Mostly too small for proper wood
Manchurian Walnut (Juglans mandshurica)
American walnut trees grow in the eastern and central United States. The English or Persian walnut trees grow across Europe, Iran and parts of Asia. White walnut or Butternut grows in the north eastern parts of the United States. Japanese walnut mainly grows in Japan.
The walnut tree is a hardwood. Hardwood trees like walnut, oak and maple are deciduous, that means they have leaves that fall off in winter. Softwood trees like pines and firs are coniferous/evergreen, with needles that stay on during the winter.
Compared with softwoods, hardwoods are generally
- Harder. Hardwoods generally are more scratch resistant and harder wearing than softwoods. They usually are higher on the Janka Hardness scale.
- Heavier. As hardwoods are denser than softwoods, they tend to weigh more.
- Darker. Hardwoods in general are darker than softwoods.
- More grained. Hardwoods have a stronger and more distinctive grain than softwoods.
- More expensive. Hardwood trees grow slower, so the wood is usually more expensive than softwoods.
- Harder to work. As hardwoods are denser, they require higher quality tools to work the wood.
In general, you want to use hardwoods for cutting boards or serving boards, as these woods are more durable and resistant to wear and use.
American black walnut trees are plentiful, but they grow slowly. Because of their beautiful wood grain and colour, there is a large demand for this wood.
When selecting a wood to use for a serving or cutting board, it is very important to choose a wood that is not toxic. A general rule is that if a tree has edible fruits or sap or similar, it is likely not toxic. However, walnut trees contain a toxin called Juglone (5-hydroxy-alphanapthoquinone). The largest quantity of juglone can be found in American or white walnut, while English walnut contains slightly less. Juglone is released by the walnut trees to limit the growth of a number of other plants near the tree and to protect its fruit husks from parasites, and it can be harmful to horses.A quality provider of cutting boards will make sure their walnut wood has been dried properly so that the Juglone will not be an issue. As long as you buy your product from a quality supplier, you should not worry about Juglone toxicity. Please note that a very few people are highly sensitive to Juglone, and they might break out in a rash when holding a walnut board, even if it has an extremely low level of Juglone.
To find the perfect type of wood for a cutting board, we can use a measure called the Janka Hardness scale. This looks at how much force it takes to press a 7/16 inch metal ball halfway into a piece of wood. The wood should have 12% moisture content and be free of knots. It is measured in pounds-force (lbf). In general, a wood with a low Janka Hardness number (e.g. balsa wood) is not very dense. It will be very soft on your knives, but knives will rapidly damage the surface of a cutting board made from such soft wood. If a wood species has a high Janka Hardness score, like bamboo, the surface will be very dense and resist knife damage. However, your knives are likely to blunt much faster. So the perfect Janka Hardness score for a cutting board is around 1000 pounds-force, just in the middle. Some of the most common walnuts: American Walnut: 1010 lbf.
The texture of walnut wood is one of the main selling points. In addition to beautiful grained wood, it can be burled and patterned in a million different ways too. If you imagine a plank of walnut wood, the largest side is the side grain. The shorter side is the side grain, and the end of each planks has the end grain. Some planks are featuring a side that is not straight, typically one that faced outwards where the bark has been taken off. This side is called a live grain.
Walnut wood comes in a large variety of colors, from almost black to almost white. The American walnut is the darkest, typically ranging from brown to black. It can sometimes have a bit of a purple tinge to it, too. English walnut has dark heartwood (the wood in the middle of the tree), but lighter brown sapwood (the wood on the outside of the tree). White walnut/butternut and Japanese walnut is usually light brown, but can be almost white to a deeper brown in color.
Walnut wood is a sustainable choice. There is a big demand for walnut wood, due to its beautiful colour, but the American black walnut and English walnut are not threatened. The White walnut or butternut is listed as vulnerable in some States and in Canada.