There are at least six different species that have been identified as having diamonds, including Salix bebbiana, S. pseudomonticola, S. arbusculoides, S. discolor, S. scouleriana, and S. alaxensis. Other species may also be found with diamonding. Diamond Willow is also a common name for Salix eriocephala, also known as Heartleaf Willow.
The diamonding is usually found with a branch at its center or is found in the Y of a tree. Diamonding in willow does not seem to be specific to an area that willows grow in, and where one bunch of willow will have diamonds, the next clump of willows may have none at all. Although diamond willow is often thought of as being a northern phenomenon, of the boreal forest, there is mention of diamond willow growing as far south as Missouri.
Diamond willow is prized by wood carvers and furniture makers for its strong contrasting colors (red and white) and its sculptural irregularity of shape. Some believe the resemblance of the fungal cankers to the vulva is partially if not entirely responsible for diamond willow's popularity.
The shape of the diamonds seems to vary from one clump of willow to the next, although there may be some general tendencies within a single species. Some stems will form long narrow diamonds; others will be short and wide. Usually all the diamonds on the stems in one clump will have similar growth patterns. If the new layers of sapwood do not move back very much each year, then the diamonds will be deep bowl- or cleft-shaped. These stems will be able to survive longer than those whose diamonds are flat and open.
The bark that is left overtop of the diamond changes quite markedly from the bark over the living sapwood. Depending on the species of willow, the living bark is usually smoother and slightly lighter in color. The bark over the diamond usually becomes rougher and somewhat darker. It also becomes tougher and adheres much more to the underlying wood. The sapwood is white to cream in color--again depending on the species, but also on the location. The heartwood is reddish-brown. This color tends to darken with exposure to light over a number of years.
If one stem in a clump of willow is affected, then all of them are likely to be. However, the neighboring clump may be completely without diamonds. As a side note, Lutz reported seeing Quaking Aspen (Populus tremuloides) in Alaska that had depressions very similar to those in diamond willow.