The wood of the spruce tree has been valued for centuries as an ideal soundboard for stringed instruments such as guitars, violins and pianos. Spruce trees thrive in cool climates of the northern hemisphere; five to six species in Europe and North America are commonly used for instruments.
A natural hybrid
Under the right environmental conditions, certain species of spruce will naturally hybridize, and the resulting hybrids can themselves cross with each other in subsequent generations. Each of the offspring are thus a unique and very diverse mix of physical (and acoustic) characteristics of each parent species.
One such hybrid that has attracted the attention of the guitar world is known as Lutz spruce (Picea x Lutzi), a hybrid of Sitka spruce and White spruce. Lutz occurs naturally in a relatively small area in Central British Columbia and the Alaskan panhandle. Such areas lie between the natural ranges of Sitka spruce along the damp coast, and White spruce, found in the drier and colder interior of Canada.
White spruce often grows with its close cousin, Engelmann spruce, and shares many of its acoustic characteristics.
Forest geneticists have determined that the crossing and backcrossing of these spruce species over thousands of years have interesting results. Hybrids growing near the coast having a higher proportion of Sitka spruce in their genetic makeup, and the trees further inland having a higher proportion of White spruce.
Why is this important to guitar makers?
Hybrids are important because certain Lutz trees combine the positive traits of both of its parent species. This is a well-known phenomenon known as “hybrid vigor.” Sitka spruce is a large tree, with strong and stiff wood, but it tends to have a relatively high density. White spruce (and Engelmann spruce) tend to have smaller trunks, and are lower in both density and stiffness than Sitka. The best Lutz spruce trees have the size and stiffness of Sitka, and the lower density of White/Engelmann spruce. The combination of high stiffness and low density can yield a superior tonewood for certain guitars, depending on the design and build.
Pacific Rim Tonewoods has been sourcing Lutz logs from some truly spectacular mountain landscapes along the Skeena and Nass Rivers in Central British Columbia. They are now testing the logs (and the soundboards resulting from these logs) for physical characteristics such as stiffness and density, in an attempt to provide the best possible tonewood to the lutherie community. Another goal is to determine whether there is a “sweet spot” within the hybrid zone, where the best combination of Sitka and White spruce grows.
Author: Dr David Olson, MD, MS