As a woodturner, my favorite hardwood is cascara buckthorn, Rhamnus purshiana, a small nondescript tree native to the Pacific Northwest. The cascara buckthorn tree has long been known for the laxative properties of its bark. Stripped in the spring, dried, bottled, and marketed as Cascara Sagrada, the bark was in such high demand in the early-to-mid 20th century that the small trees were severely overharvested. Sadly, harvesting cascara bark kills the tree, and so throughout much of its native range, primarily the western side of the Cascades in the Pacific Northwest, cascara, never very abundant, became quite scarce. After a 2004 ice storm, several of the larger, more exposed trees on my property were severely damaged, with their branched tops bent 90 degrees with the wood splitting at the bend. I cut these trees into long sections, sealed them, and put them aside to dry. I stored the 4-to-6-foot long pieces in an old leaky barn near a creek, so there was plenty of humidity year-round. Two years later, I found that more than half of the wood had developed some color, and all of it was totally sound and dry enough to turn.
When freshly cut, cascara sapwood is a pale yellow, and the heartwood, which makes up about a third of the diameter of the trunk and larger branches, is almost a pumpkin orange. As the wood dries, the sapwood seems to get paler, and the heartwood color becomes more muted. The wood undergoes color changes that range from a ring of pale blue just under the cambium to pink or purple streaking through the sapwood. Some pieces will develop bluestain all the way to the heartwood. These color changes seem to be related to having bark and lichen – remain on the wood — debarked pieces do not change color, at least in my experience.
Even without the color band, cascara can be very beautiful. The fine-grained sapwood displays a subtle chatoyance, almost like the moire patterns in fine curtains. On one of the larger trees I took down, the cross-section revealed that every growth ring was finely rippled, like the edges of paper cupcake pan liners.
I am most careful not to put my hands near my mouth when working this species. Otherwise, I take only normal precautions against dust and chips when turning cascara, and I have experienced no side effects from the bark, even when turning it green.
Dry cascara turns easily. The wood is fairly hard, about like big-leaf maple, and shows little tendency to chip. It polishes up beautifully. I have used only clear shellac or, on the weedpot, just beeswax, to avoid darkening the colors. A fascinating and unexpected fact about cascara, which I only learned recently, is that it is closely related to pink ivory, Rhamnus zeyheri. Pink ivory, which grows in southern Africa, is considered one of the most rare, expensive and beautiful woods in the world. In my opinion, cascara, its humble North American relative, is also deserving of some respect.