Only 2% of paulownia wood distributed in Japan is domestically sourced. Faced with this crisis, Yasuo Nezu plants 400 saplings annually on abandoned farmland, cultivating the wood himself over 15 years. He revives 100-year-old paulownia chests using traditional techniques that leverage the wood's lightness and humidity-regulating properties, and is even experimenting with it as a core material for snowboards. How will his work, "sowing seeds and shaping the future," intertwine with our lives? He shared his long-term manufacturing philosophy, from its excellent insect and fire resistance to new concepts for paulownia boxes designed to protect rice and cameras.
Yasuo Nezu
The 4th generation owner of Kirisho Nezu, a paulownia product specialty store founded in 1917 in Minakami Town, Gunma Prefecture. Starting as a paulownia forester, the company has produced numerous paulownia products since its founding, including paulownia geta, paulownia chests, architectural materials, and household goods, adapting with the times.
(*Article content is based on information at the time of the interview)
#1 Paulownia wood grown from seeds
Investing for 30 years ahead. 400 trees to protect domestic wood.
―― You've been growing saplings yourself from the start?
Yes. We grow paulownia from seeds, using the "seedling" method. There are only two paulownia businesses that do this from seed: my master in Aizu, Fukushima Prefecture, and us.
Grafting doesn't really take root well. There's also a method called root division, where you cut and separate the roots, but if the original tree has a disease, it will be inherited.
However, pure paulownia that has germinated from a seed doesn't inherit any diseases or anything. So, we start paulownia cultivation from the moment the seeds sprout.
―― Can you tell us about the germination process?
After soaking the seeds in water, we manage them in a small plastic tent. We have equipment to maintain temperature and humidity, but there are still many failures.
Also, we do something called "stooling." Once it grows big, we cut it right back at the base. Originally, it's just one stem.
We cut it from the base, and then make new shoots emerge from the side. When you cut the tree at the base, the new shoots that emerge after stooling grow faster than if you just let the original one grow for a year.
After all, when something alive is cut, it feels its life is in danger, so it tries to grow faster and faster.
―― How long does it take until it can be harvested?
It takes about 15 to 20 years for it to become a large, magnificent tree.
From there, it takes another 7 years for natural drying and lye removal, and even after it's made into planks, it still takes time. So, it takes about 25 to 30 years until it can actually be used.
―― For 30 years later.
This is completely an investment in materials for our future. Currently, domestic wood is gradually disappearing.
98% of the paulownia products currently distributed in Japan are made from Chinese or foreign wood.
Paulownia products made from Japanese paulownia account for only 2% of all paulownia distributed in the world. And it is said that this will drop to 0.5% by 2035.
If that happens in 10 years, we thought we'd have no choice but to do it ourselves to consistently insist on and continue using domestic wood, so that's what we're doing.
―― How many saplings do you plant each year?
About 400 saplings per year. Currently, like Minakami Town, many regions have an incredible amount of abandoned farmland, don't they? Minakami Town has an area of abandoned farmland equivalent to 35 Tokyo Disneylands, and we rent all the places that have become overgrown and unmanageable and plant trees there.
Normally, trees shouldn't be planted directly in fields, but paulownia is the only tree that is treated as a "special forest product" that can be planted in fields, just like mushrooms. So, we can plant them immediately after renting without the need for agricultural land conversion procedures.
―― Why has the number of paulownia growers decreased in the first place?
Well, even if you grow seedlings and plant them, it's not a very profitable business, so successors kept disappearing.
Minakami Town also wanted to solve the problem of abandoned farmland, so the agricultural and forestry department of the town office searched nationwide, found my master in Fukushima, and contacted him. The town office also cooperated, as this initiative would lead to solving regional issues.
#2 The wisdom of paulownia boxes rooted in daily life
Breathing, fire-resistant, and rot-proof. The mysterious wood revealed by science.
―― Why are chests made of paulownia wood?
There are several reasons. First, it's the lightest wood in Japan. Do you even know the unit for paulownia chests?
It's counted in "sao" (rods). In the past, people would pass rods through the metal fittings of paulownia chests and carry them on their shoulders.
Also, zelkova (keyaki) is heavy, isn't it? Paulownia is one-sixth the weight of zelkova. It's that light and easy to transport. And it has the best humidity control properties among all wood types.
Because the wood breathes, it maintains a stable humidity of 40% to 50% throughout the year, which protects the contents from moisture and prevents sudden drops in humidity, thus reducing stress and preserving the quality of items well.
―― I often hear about its insecticidal properties as well.
What's interesting about paulownia wood is that it's the only alkaline wood. All other woods are acidic. And insects and germs can't eat alkaline things. Mold also can't reproduce.
But paulownia wood is inherently a wood that insects and mold can't get close to. If you make chests out of other woods, they will eventually get moldy or eaten by insects.
Insects dislike paulownia, just like how humans would feel if they drank bleach (an alkaline disinfectant).
Because of this, it has been treasured for storage and preservation since ancient times, not just for leather products and kimonos, but also for making furniture and boxes, as it maintains their condition.
―― Paulownia is also used for storing food, such as rice bins, isn't it?
Yes, it's not just that, it's also effective for food preservation.
Things like rice and bread are all slightly acidic. It's said that after milling, the quality deteriorates and the eating quality declines, but because paulownia wood is inherently alkaline, it causes a neutralization reaction inside, stopping oxidation. It's a box that preserves deliciousness.
It's hard to say how people in ancient times discovered these properties, but now the benefits of paulownia have been scientifically elucidated, and it is said that paulownia is the best wood for storing and preserving things.
―― I heard it's also resistant to fire.
Paulownia wood is said to be light because its cells and tissue fibers are shaped like styrofoam, meaning it's a porous wood with many air layers.
And when the surface is burned, a carbonized layer forms, which blocks the supply of oxygen, preventing the fire from reaching inside. Even if fire is applied to one side, the surface will char black, but the inside will not burn.
There are many stories of storehouses completely burning down in fires, but only the paulownia chests remaining, with their contents intact. This is also why old safes always had paulownia lining on the inside.
―― Paulownia inside safes too?
Yes, safes have always had paulownia lining on the inside.
Even if you buy a new safe today, it might not have it. But even in my grandfather's generation, there were orders from companies to make chests that fit perfectly inside the safes they had made.
So, even if the safe itself was damaged, the paulownia inside would ultimately protect the contents. Most old safes had paulownia lining on the inside. It's quite amazing.
