By Bob Gander ©1997, revised 1998-02-20
Diamond willow is not a species of willow, but rather it is apparently the result of attack by one (Valsa sordida) or possibly more types of fungus on several species of willow (Lutz). I have used the word "apparently" because, although this is the accepted explanation, Mr. Lutz is careful in his wording since he relied on evidence for this from another source (see below). From my own search of the scientific literature, I have not found a second reference to confirm or refute the fungal explanation. The article by Mr. Lutz seems to be taken as the definitive statement on the subject. Cankers, or diamonds, form as a result of the tree's response to the fungus. The diamonds are actually more like elongated ovals with pointed ends. In my observations, if one stem in a clump of willow is affected, then all of them will 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.
In my experience there are 4 or 5 species of willow that grow cankers in response to the fungus. The cankers seem to result from the tree "growing away from" the site of attack. This usually happens at the crotch of a branch on a larger branch or main stem. If the branch is relatively small it seems to die very quickly. If the branch is larger, it may continue to grow and the "diamond" is formed on the branch and the stem. By growing away from the fungus, I mean that new layers of growth occur further and further away from the site of the fungal attack. Thus the affected area gets larger and deeper. If the tree has been affected in several places close together, then the diamonds "run into" each other. This can result in pronounced ridges if some sapwood continues to survive, or it may "strangle" the small ridge of sapwood, which then dies.
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 over top 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.
Lutz identified six species that he identified that had diamonds. Apparently Baxter and Wadsworth identified a seventh species. One of my future projects is to get some training in willow identification. From my reading, there are over 100 species of willow in North America, and some of these hybridize in the wild. Thus proper identification can require careful observation not only of bark and leaves, but also growth habits, flowering and seed development. The oldest sample of Bebb willow that Lutz reported was 146 years old! It had a diameter (inside the bark) of 6.6 inches. It should be noted that both Lutz and Baxter and Wadsworth made their observations in Alaska, with the exception of Salix discolor which was seen near Edmonton, Alberta. [Lutz states it was from near Pigeon Lake, which is where my parents' had a cottage, and thus where some of my earlier willow hunting "expeditions" were mounted.]
Salix bebbiana Bebb willow Lutz Salix bebbiana var. perrostrata smooth Bebb willow Lutz Salix pseudomonticola park willow Lutz Salix arbusculoides littletree willow Lutz Salix discolor Lutz Salix scouleriana Scouler willow Lutz Salix alaxensis feltleaf willow Baxter and Wadsworth
Where to find diamond willow
Diamond willow is found throughout much of Alaska, the Great Plains, the parklands, and the boreal forest. I have personally observed some in the Canadian (or Laurentian) shield in Ontario and Quebec. When I lived in New Brunswick for five years, I did not see any growing there. However, via the woodcarver listserve, I have received reliable reports of its being in New York State. My understanding is that Bebb willow is one of the most prevalent species of willow found on the Great Plains of North America. From my backpacking in the Canadian Rocky Mountains, it does not seem to occur at elevations above those of the foothills.
Willows, in general, like low lying, wet areas. My rule of thumb is: where the mosquitoes are worst, there you will find willow! Good diamond willow can be found along riverbanks and lakeshores, beside sloughs and farm dugouts, and in bogs and swamps. Beware of people who say, "the best diamond willow grows at [insert their particular location]". They obviously haven't seen MY willow. <wink, wink, grin> I know that when I came to Saskatoon, I was told the best diamond willow was at a lake about 45 minutes west of the city. However, the best that I have ever found anywhere is on the riverbank right here in the city. That is not to say that there isn't even better diamond willow somewhere else; maybe right near you!
Working with diamond willow
Two pieces of very good diamond willow from west of Saskatoon are shown in the following image. The color is a bit misleading; they should be gray rather than bluish gray. (These two pieces will be featured in a later WWWoodcarver Ezine article on making ridges in diamond willow.) They are approximately 1.5 m (5') long and 5 cm (2") across at the base (depending where you measure). The bottom ends are darker as there was a thick layer of leaf mold around them, and I cut them as close to ground level as I could. Although they came from the same grove of willows, they were not close together. The right hand one has deep diamonds with pronounced ridges between them, whereas the one on the right has flatter, more open diamonds. At the top of the right hand one, you may be able to notice a patch of a slightly different color. This is lichen which very frequently grows on the willow, particularly on the bark over the diamonds. Both pieces were dead when harvested. Once the bark was removed the sapwood was found to be in good condition and creamy in color. If the willow is cut green, or has died recently, the sapwood is white. Some day when I own a bathroom scale, I am going to weigh a piece before and after debarking it. My estimate is that a large fraction of the weight (perhaps as much as a quarter) is in the bark.
This image shows a piece where some of the bark has been removed. The right hand fork was alive when this piece was harvested. Each fork is only about 2.5 cm (1") in diameter. The bark over the living sapwood is relatively smooth. The inner bark is no longer green, because the piece was stored for over a year before I started to work with it. The fork on the left had already died, so the sapwood is a darker shade with some spalting already apparent. Immediately below the crotch, I have exposed some heartwood from a "diamond". The shine from the photo somewhat masks the light reddish brown color. Just below the bare heartwood is a strip of inner bark. Over the heartwood this inner bark is hard and shows a "grain" almost like wood; over the sapwood the inner bark is not quite as hard and more fibrous in texture and behavior. Below the debarked area there is a diamond. There is also a diamond in the crotch that isn't visible in the image. For some reason the fungus had "bridged" between the two diamonds to create the strip of heartwood. On the left-hand fork, the brown parts are actually heartwood not associated with a diamond. This often occurs. My guess is that as the stem started to die (perhaps over several years), the sapwood wasn't built up or was converted to heartwood as normally occurs in trees. For some reason the left-hand fork died even though there was a large part of it unaffected by diamonds, and therefore, presumably still able to carry sap. And yet other stems will grow for several years along only a very narrow ridge (as was the case for the right-hand piece in the first image).
Diamond willow is an excellent wood to work with, in my opinion. For carving and making craft objects, the irregularity of shape can greatly add to the esthetic appeal of the item. The species that form diamonds seem to grow quite slowly, so the grain is closely spaced. The heartwood is similar to basswood in terms of how it feels to carve and the amount of detail that can be achieved. I mostly carve with knives and gouges, so I can't comment on power carving. However, I do use ruby carvers on a "Dremel" to sand some of the hard to reach parts or to contour the base of a branch. This works well and doesn't seem to create undo amounts of "fuzzing". The sapwood tends to be somewhat harder than the heartwood. If the stem has been cut green, then this is more pronounced. If you try to carve while the sapwood is still "wet", it can be quite stringy. Your tools will have to be very sharp to avoid tearing the wood fibres.
Because the piece of wood is inherently at least partly dead, there are almost always some "standard" fungi at work causing some rot. One of the characteristics of diamond willow is that it weathers very well. It was used extensively on the prairies for fence posts. This is true of the heartwood only. The sapwood is quite susceptible to rot; so most choice pieces will have small parts of the sapwood that is at least spalted if not completely rotted. Also at the base of a main trunk, the center part may be weakened from rot. The bark over the sapwood also tends to fall away more readily than that over the diamonds. Although the rotting can substantially weaken a piece of wood, it can also greatly add to the visual effect of the diamonds. I have worked with several pieces where all the sapwood was so rotten that I cleaned it off and was left with diamonds that are raised above the surface of the underlying heartwood. Badly spalted wood can be hardened with one of several products now available. I use cyanoacrylic (Super) glue. This can be purchased from hobby stores in larger bottles (8 oz) than is usually available at a hardware store. Be careful when applying it--I can never get the stuff to bond something I want bonded, but I can readily bond my fingers together! You should also use a mask with organic vapor filters, particularly if liberal amounts are applied. Cyanoacrylic glue is exothermic; that is, it gives off heat as it sets. This leads to a lot of vapor also being given off.
Another common "feature" is the presence of boring insects and their tunnels. Most of the insects seem to live in the bark, so once that is removed the insects should be gone. The "tunnels" created between the bark and the wood will now be fully exposed, and they create some interesting patterns. The holes that have been eaten directly into the wood are usually black; so they can add some tonal quality and some mystery to a piece. If the piece is to be used outdoors, I usually try to fill all the cracks and holes. I often use a two-part clear acrylic epoxy to fill the holes. To do this, try to determine if the holes are interconnected, and, if so, which orientation is best to fill them as the epoxy flows in. I cover the downstream exits with masking tape until the epoxy has cured.
Carved pieces can be left with tool marks, or the wood can be sanded to good effect. For pieces that will be used inside and will not see rough duty, I usually sand to 400 grit. For outside pieces or those that will be handled a lot, I usually sand to about 320 grit. My personal preference is for a matte or low lustre finish, and I really like the feel of finely sanded wood. Therefore, my finish of choice is oil, Varathane Natural Finish, tung oil, or Watco oil. I think that Danish oils tend to enhance the effect that light has on darkening the heartwood. This, however, is only anecdotal--I have never done a careful comparison. For items that will be handled or be outdoors, I prefer to use a satin gloss urethane. Any number of craft items can be made from diamond willow.
H.J. Lutz, "Observation on 'diamond willow,' with Particular Reference to Its Occurrence in Alaska", The American Midland Naturalist 60(1): 176-185, 1958.
Mr. Lutz cites a report by D.V. Baxter and F.H. Wadsworth ("Forest and fungus succession in the Lower Yukon Valley", University of Michigan, School of Forestry and Conservation, Bul. 9. 52 pp.). This report apparently is the only evidence of Valsa sordida being the fungus responsible for forming the diamonds. I would be greatly indebted to anyone who may be able to send me a photocopy of this report. I would also appreciate any other references you may have to the cause of the diamonds.
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