Wood crotch develops when a tree trunk splits up in two or more branches. The place where this happens has different shaping of the wood pattern which creates a special look in the cut pieces. It’s not easy to come across high quality crotch slabs because they are challenging to dry. During the drying process, the crotch is prone to cracking and twisting like the end of the grain. Good crotch pieces can be found depending on the type of wood. Oak and ash crotch are harder to find, while walnut is more available and is often of a good quality. In the picture below there is an example of a table that I made in walnut with a beautiful crotch pattern.

Burl wood is a type of abnormal fast growing part of some trees. This happens because the tree has experienced some sort of stress or damage; it is often caused by a fungal or insect attack. Not many trees produce burl wood which makes it rare especially when good quality is demanded. If found, it can result in magnificent pieces. 

 

The direction of the growth of the wood fibers has a lot of influence on how the wood looks.  Depending on how the tree grows and is cut this will result in different grain pattern. 

On the picture to the left we see in given order :

1. diagonal grown grain (straight grain pattern not cut along the axe)
2. irregular grain (wood fibers varys in direction of the vertical axe, arround knots for example)
3. straight grain (normal growth)
4. wavy grain (the direction of the fibers constantly changes)
5. spiral grain (tree trunk grew twisted, fibers twist constantly to left or right)
6. *interlocked grain pattern(fibers twist every grow period in different direction)

*Interlocked grain pattern comes from where the tree fibers twist during growth. In a way that results in a spiral orientation of the fibers up the trunk rather that the normal parallel to the center-line of the tree. On some of the trees that do this, the spiral changes direction from year to year, the result is interlocked grain and it is one of the reasons for such figures.

It occurs in many hardwoods, and although it often produces a visually stunning figure, such woods is difficult to work because the interlocked grain tends to tear out in planing and other operations. Also, such wood is usually exceedingly difficult to split.