Douglas Brooks recently forwarded an email from Vergennes, Vermont, with a query he had received from a New Zealand construction wood supplier who imports Japanese cedar (sugi) and cypress (hinoki). The supplier, knowing of Douglas’s knowledge of Japanese boatbuilding from a profile about him in WB No. 280 and numerous articles he has written over the years, asked about the boatbuilding potential for these woods.

“We are working with a company in Italy,” the query stated, “that caters to the design and build industry for luxury boats, both small and very large. Last month we sent samples of hinoki and sugi from Yoshino to them, which they took to a recent trade show in Milan. This in turn caused some interest, as the more traditional timbers such as teak and mahogany are now becoming too expensive and extremely hard to find in legal and traceable supplies. I have attempted to find creditable research that explains the properties of either sugi or hinoki in relation to marine use. I have found timber industry references to hinoki performing in damp and semi-wet areas such as bathrooms and kitchens, but nothing about the use of hinoki or sugi in the marine world.”

In response to this request for research findings, I corresponded further with Douglas, exchanging experiences that he and I have had in our visits to Japan, his as a scholar studying Japanese boatbuilding skills and mine as a collaborator with Japanese wood scientists.

Geography

The land area of Japan is slightly smaller than that of California, and the country has a population that is 40 percent of that of the entire United States and more than three times the population of California. As you might guess, land in Japan is an extremely dear commodity. I recall riding on rural roads that had no shoulders; carts and motorized vehicles vied for space on the roadway, and rice fields were plowed to within inches of the pavement.
Land outside of cities, shrines, or other protected areas is almost entirely used for agriculture or commercial forestry. Since much of Japan is covered with steep mountains, only about 12 percent of the land area is devoted to agriculture. A surprising 68 percent is forested, with roughly 19 percent in relatively undisturbed primary forest, including shrine areas. The rest is mostly managed for timber production, with about equal shares in natural regeneration and planted forests.

Forest Types

Most of the native trees of Japan, especially on the island of Honshu, would be immediately recognizable to anyone living in Europe or eastern North America.

Yet a drive through the Appalachian Mountains of Virginia would look entirely different from any ride around central Honshu. The U.S. trip would reveal a mix of hardwoods with occasional conifers. The Japanese trip would be dominated by planted conifers, mostly two species: sugi (Crytomeria japonica) and hinoki (Chamaecyparis obtusa). Extensive forest destruction during World War II prompted a countrywide massive tree-planting program, emphasizing sugi and hinoki, two fast-growing and revered species. Sixty years later, 70 percent of planted forests consist of just these two species, with sugi pre-dominant. The result is a surfeit of these trees, and among the solutions being explored are developing new products, such as cross-laminated timber, for the construction industry or finding new or expanded export markets for sugi and hinoki.

Wood Properties

Despite the long history of the utilization of sugi and hinoki for various products in Japan, the export market has been confined mostly to a few finished products such as soaking tubs or extracted oils. As a consequence, English-language data on basic wood properties is scarce to absent. If my Japanese wood-scientist colleague were still living, I would have contacted him at Hokkaido University. Instead, I mounted a frustrating search that finally turned up two research papers in English that provided some mechanical properties and design strength comparisons. Although their testing was limited, when combined with information on sugi that I gleaned from The Wood Database, I concluded that sugi is a moderately weak wood, comparable to Atlantic white cedar (Chamaecyparis thyoides), western red cedar (Thuja plicata), or incense cedar (Calocedrus decurrens). Hinoki is about one-third stronger than sugi and is comparable to European spruce (Picea abies), American shortleaf pine (Pinus echinata), and the weaker grades of Douglas-fir (Pseudotsuga menziesii).

What about durability in wet environments? Hinoki heartwood is consistently rated as “very resistant,” or class 1, the highest international rating between 1 and 4. Sugi, on the other hand, is quite variable and can range over the full scale from 1 (very resistant) to 4 (non-resistant or perishable). The reasons for this variability might be the soil-mineral characteristics of the growing location, growth rate, or even that sugi has evolved into different varieties or races as a result of purposeful or inadvertent breeding over many centuries.

Two wooden boxes inscribed with Japanese lettering.Richard Jagels

These two masu, used to share sake while the author was traveling in Japan in the 1980s, are made of hinoki wood. They are signed by Japanese wood scientists, including the author’s colleague of many years, Kazumi Fukazawa, who has since died.

Wood Traditions

Despite the high value of hinoki for durable construction, exemplified by the long life span of temples and shrines built of this wood, tourists to Japan often have a first glimpse of hinoki wood at a restaurant dining table in the form of masu: small, square wooden boxes filled with sake, a Japanese rice wine. Originally, these hinoki boxes were produced as measures for uncooked rice or soy sauce. But a tradition emerged of drinking sake from them at weddings or other happy events. Masu are often signed by friends and saved as mementos of an event, as shown in the accompanying photo.

Japanese traditions and Shinto rituals are deeply embedded in hinoki and sugi trees. Some temples built of hinoki are over 1,000 years old, and individual trees of sugi can be over 2,000 years old. Over time, these ancient wooden temples and trees take on spiritual attributes, to the extent that younger trees growing in the area are believed to have superior properties. The highly revered Jomon sugi, located on Yakushima Island at an altitude of 1,934m (6,345′ ), is estimated to be between 2,170 and 7,200 years old. Not unexpectedly, sugi trees growing on Yakushima are highly prized, and the oldest ones are given a special name: Yakusugi. Logging of these endangered Yakusugi trees ended in 2001.

When I visited Japan in the 1980s, peeled Yakusugi poles were most prized in a traditional Japanese house for making toko-bashira, a pole installed in the corner of a tokonoma, a recessed space or alcove for ritual items and artwork. It might seem wasteful to non-Japanese to use this highly valued wood for a decorative feature in a house, yet tradition often trumps the pragmatic in Japan. An immersion in Japanese culture would be required to understand why thousands of single-use, sake-quaffing masu are produced each year when many boatbuilders are unable to afford this valuable wood. I suppose one could make a similar comparison for teak salad bowls versus boat decking.

Regional Wood

The variability in the decay resistance of sugi wood was quite a surprise to me. I have rarely seen such wide variance in another wood. If its characteristics are due to regionality, that would support the belief among Japanese woodworkers that sugi from particular regions is superior to that of other areas.

Douglas told me that Japanese boatbuilders with whom he apprenticed preferred miazaki cedar grown near the town of Obi, hence it is also known as obisugi. Obi is a historically important center for intensive forestry, dating back to the Edo period (1603–1868). Perhaps tree-selection programs begun in that region hundreds of years ago have changed the wood characteristics of sugi grown in the area.

Capitalizing on tradition, regions that have provided timber for the construction of important shrines or temples in the past now often use their history to promote the quality of current hinoki and sugi trees. Yoshino, the region mentioned in the letter from New Zealand, claims to be “Japan’s oldest man-made forest, which was planted about 300 years ago.” Hinoki and sugi from this forest were used from the 15th through the 17th centuries to build temples, shrines, and castles in Osaka, Nagoya, and Fushimi.

The Japanese timber company Sumitomi Forestry plans to build the world’s tallest wooden building (350m, or 1,148′ tall) in Tokyo to celebrate its 350th anniversary in 2041. If this structure includes cross-laminated timber made with hinoki and sugi, it could help to reduce the surfeit of sugi trees that has led to Japan’s most common disease, seasonal allergic rhinitis. About 20 million people, or 20 percent of Japan’s population, develop pollinosis from breathing sugi pollen each year, an unanticipated and unwelcome consequence of the extensive planting of this tree. The email from Douglas suggests that boatbuilders outside Japan might also get a chance to try sugi, and possibly even hinoki, as more trees reach commercial harvest age.

Dr. Richard Jagels is an emeritus professor of forest biology at the University of Maine, Orono. Please send correspondence to Dr. Jagels by mail to the care of WoodenBoat, or via e-mail to Senior Editor Tom Jackson, tom@woodenboat.com.