Lutz Spruce and “hybrid vigor”

by Dr. Dave Olson

The wood of the spruce tree has been valued for centuries as an ideal soundboard for stringed instruments such as violins, pianos, and guitars.  Spruce trees thrive in cool climates of the northern hemisphere, and 5-6 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 attacted 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 resulted in the 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?

It is 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 (see figure).   We have begun, for the first time, to test 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.

A NEW GUITAR FROM TAYLOR

In January of 2016, Taylor Guitars introduced a revision of their venerable 500 series  guitar, revoiced to take advantage of the unique sound that Lutz spruce can deliver.   Taylor’s Master Luthier, Andy Powers, finds that the Lutz from PRT is similar to Adirondack spruce, in terms of its acoustic characteristics.

Although Lutz has been successfully used for decades by custom luthiers, the new Taylor 500 series represents the first time a major manufacturer has featured Lutz tops in a widely available production model.    This can thus be considered the  “debut” of Lutz spruce to the wider guitar community.