There may be no better symbol of Japanese whisky’s spirit of resilience than Mizunara oak. And the narrative of Suntory’s historic Yamazaki Distillery itself is interwoven with the history of Mizunara oak.

When founder Shinjiro Torii established Yamazaki Distillery in 1923, it was the nation’s first dedicated whisky distillery. Torii’s vision was not to merely replicate Scotch, but to make a whisky that was authentically Japanese, attuned to the Japanese palate which values balance and subtlety. But one major challenge was the distillery’s isolation, with no nearby peers and – unlike Scotch distilleries – no opportunity to trade knowledge or spirit with rival producers.

The fledgling whisky distillery had to innovate internally and become entirely self-reliant, developing a versatile production to create many whisky styles in-house. This necessity and resourcefulness became a virtue. The House of Suntory today describes this philosophy as “Tsukuriwake”, or artisanship through diversity of making. In essence, Tsukuriwake is a single distillery creating the illusion of a multi-distillery blend through diversity of production. This means producing an astonishing variety of whiskies by varying every conceivable parameter – from the mash ingredients (barley varieties) to the still shape (8 pairs of different stills) to the cask type.

One of the greatest canvasses for Tsukuriwake’s diversity is cask maturation (also explored in this review of the 2024 Tsukuriwake Collection), where each cask imbues the spirit with different aromas and flavours over years of maturation. These include ex-bourbon barrels and hogsheads made of American white oak (imparting vanilla, coconut and oak lactones), Spanish oak sherry butts (bringing dark fruit, chocolate and spice notes), French oak wine casks (which add ripe berry and tannic nuances), as well as puncheons and port or brandy casks on occasion. And, of course, there is Japanese oak – Mizunara – the hallmark “instrument” in that orchestra which lends a distinctly Japanese melody.

And yet, despite Mizunara’s importance in Yamazaki’s history, its role arose as an accident of history.

Mizunara (Quercus crispula), was not the first choice for Japanese whisky makers – it was in fact the last resort. During and after World War II in the 1940s, Japan faced dire shortages of American and European oak. At the same time, domestically-made whisky was in high demand (bolstered by occupying Western troops thirsty for whisky).

In this bind, Japanese distillers turned to what they had: a local timber called “water oak”. Named after its high moisture content, Mizunara was known for fine furniture and temple construction, but no one had seriously used it for maturing whisky. Out of sheer necessity, early postwar Japan began coopering Mizunara barrels – and quickly discovered why nobody had before.

Working with Mizunara was frustrating for coopers (barrel-makers). Unlike European or American oak, Mizunara grows slowly, often with a wild, gnarled form. This means that it might need to live 200 years or more before it is large and straight enough to yield staves for a barrel. By comparison, American white oak is harvestable in less than half this duration.

True to its “water oak” name, the wood’s cellular structure holds a lot of moisture, and this must be slowly dried. It has to be air-seasoned for at least 3 years (versus 1–2 years for other oaks) to reduce its moisture and tannins. And when the cask is assembled, it’s notoriously leaky. The grain doesn’t seal as tightly as European or American oak, meaning whisky can seep through the seams and evaporate at higher rates.

Were Mizunara’s challenges outweighed by its flavour?

Suntory later noted, the first attempts were “not palatable”. Younger whisky aged in Japanese oak was described as overly woody or tannic, with unusual aromas that didn’t mesh with the lighter Scotch-style malt of the era. However, patience was the key. It took Suntory years (and some serendipity) to understand that Mizunara’s magic only emerges with time. Fill them for a short time and you get aggressive woodiness. But let a whisky sleep in Mizunara for 15, 20, 25 years and something remarkable happens: the sharp edges smooth out, and the whisky takes on a rich coconut sweetness, with scents of sandalwood and temple incense. Suntory's Chief Blender Shinji Fukuyo describes this as "the aroma of walking onto the wooden beams of a temple and deeply breathing incense-filled air right as the rainfall ends."

This distinctive temple incense-like note was unlike anything from American or European oak. The revelation was clear: Mizunara, for all its difficulty, could give Japanese whisky an identity all its own. What had begun as a desperate wartime improvisation was now a secret ingredient in crafting world-renowned Japanese whisky.

Obtaining and coopering Mizunara remains a careful undertaking for Suntory today. The ancient oak is sourced from protected forests in Hokkaidō and other northern regions, and sourcing can involve complex negotiations and auctions. Japanese law even limits how much Mizunara can be felled – trees in national forests must fall naturally before they can be milled.

Once acquired, the logs begin their slow transformation at facilities like the Oumi Cooperage, a family-run cooperage not far from Yamazaki Distillery. There, seasoned craftsmen painstakingly saw and air-dry the wood, seeking staves with perfectly straight grain to ensure a watertight seal for the barrels. Oumi’s CEO lamented that “one could be forgiven for not wanting to work with this difficult material.”

The numbers put this rarity in perspective. Out of Suntory’s approximately 1.6 million whisky barrels in storage, less than 1% are made of Mizunara oak. This scarcity means that Suntory treasures every Mizunara barrel and uses each to its fullest potential. A new first-fill Mizunara cask yields the most intense flavours – akin to a strong first brew of tea. This might have to be blended or further aged to tame it. The second and third fills, however, are golden opportunities: by now the wood has “broken in” and can cradle a whisky for a long maturation. A fourth or fifth-fill Mizunara cask, having given much of its strong spice already, might then be used more sparingly – for instance, to finish a batch of whisky and lend a delicate top-note of incense.

Even when a Mizunara barrel seems “exhausted” after many decades, Suntory can rejuvenate it instead of discarding it. In a process similar to practices in Scotland, the cooperage may shave off the inner layer of oak and re-toast or re-char the staves, exposing fresh oak beneath the surface for the spirit to interact with. This essentially gives the venerable cask a new life.

Even though Mizunara casks represent a small fraction of the blend, you can still sense their influence in the familiar Yamazaki 12 if you know to look for it. The familiar Yamazaki 12 itself embodies the Tsukuriwake philosophy and the fruits of Suntory’s diverse production. It was not made of a single cask – it was a complex composition drawn from Yamazaki’s multifaceted stock, made with a blend of spirit aged in American, Spanish, French and of course, Mizunara oak.

Just this year, Yamazaki further ingrained Mizunara‘s legacy in the limited edition Yamazaki 25 Year Old Mizunara Edition. Whereas core range Yamazaki expressions and even the Yamazaki 55 Year Old only contain a component of Mizunara-aged spirit, the Yamazaki 25 Year Old Mizunara is 100% matured in Mizunara oak. This is the oldest fully Mizunara-aged Yamazaki whisky in history yet!

Last month, I had the eye-opening opportunity to join Andrew Pang, Suntory’s Southeast Asia Brand Ambassador, at a special luncheon to learn all about the influence of Mizunara oak in Yamazaki’s whiskies.

We tasted through a special range of component malt samples that showcase individual cask styles of Yamazaki – including a special expression that contains a portion of Yamazaki 25 Mizunara. Let’s start our tasting journey!

Sample 1: Yamazaki American White Oak 12 Years Old

Nose: Distinctly creamy, with a honeyed sweetness sitting with a light oak presence. Sweetness here isn’t heavy, coming through as bright and almost airy, with threads of vanilla softening the profile. A light dusting of toasted coconut flakes at the edges.

Palate: Opens clean and bright, driven by a malty core that feels both crisp and rounded. Plenty of ripe orchard fruits with fresh apple and pear at the forefront, joined by citrus zest and flashes of candied dark fruits. Some ripe bananas adding a gentle tropical depth, and some sweet touches of maltose hard candy and a soft layer of butterscotch.

Finish: Medium in length, turning toward vanilla, coconut, butterscotch and warming spices. A faint orange peel bitterness cuts through the sweetness.

Impressions: 

This distillery sample of Yamazaki 12 matured in American white oak sets a good baseline for the whiskies to come, as it leans into its neutral puncheon cask character with that clear thread of honey, orchard fruits and creamy vanilla tones. This is less dramatic and more about a clean, integrated showcase of Yamazaki’s orchard fruit-influenced spirit against the neutral backdrop of American oak influence.

Sample 2: Yamazaki Mizunara Oak 12 Years Old

Nose: Creamy yet more overtly spiced than the American oak sample. The aroma is bright and malty, but showing a distinctive resinous character that certainly derives from the Mizunara. Toasted coconut comes through very clearly, supported by crisp apple notes and a gentle layer of light caramel that comes closer to smooth crème caramel beneath the spice and fruit.

Palate: Wow, this is unexpectedly tropical! A surge of coconut leads the first impression, layered with spice, most notably candied ginger lending both sweetness and heat. It feels very generous and expressive, full of wood spice aromatics balanced against creamy coconut. Honeyed sweetness runs through the middle, joined by candied pineapple and the grainy presence of toasted barley. It’s bold, with spice and fruit woven tightly together.

Finish: The finish holds onto that resinous edge that feels tied to the Mizunara wood and has a lingering warmth. A light drying oak sensation follows, tapering off into a hint of mild sandalwood note.

Impressions:

This Mizunara-matured Yamazaki 12 sample already shows the hallmarks of the cask, with that faint sandalwood note beginning to appear alongside a resinous texture in the aftertaste. Andrew pointed out that at 12 years of age, some rough edges still remain, with the resinous quality still prominent, and a structure that could still be fuller (compared to a core range Yamazaki 12 which is made with a large component of Golden Promise Barley, this distillery sample is pretty light in texture!).

Even so, the flavours are strikingly tropical, with coconut and candied pineapple standing out, supported by ginger spice and honeyed sweetness. Compared with the American oak sample, this definitely feels more exotic and generous, with spice and tropical fruit carrying more weight. It’s beginning to show promising complexity with that the bright malt core of Yamazaki layered with Mizunara’s signature aromatic spice – even if this youthful expression still needs time to fully refine its character.

Sample 3: Yamazaki American White Oak 18 Years Old

Nose: Immediately richer and more rounded than the 12 Years Old American oak sample, with a deeper honeyed sweetness at its core. Light wood spice weaves through, along with a faintly musky or slightly musty malt note that gives the aroma a bit more maturity and heft. It’s both very spiced and honeyed, with the vanilla notes playing a stronger role.

Palate: It turns creamy and full, the texture thick and viscous, almost oily, showing layers of rich vanilla and coconut that expand across the tongue. It feels concentrated and cohesive, with the sweetness of the oak-driven vanilla firmly anchoring the palate.

Finish: Smooth and extended, leaving behind soft vanilla and cream tones. Delicate orange blossom floral notes appear to lift the tail end of the experience with a gentle brightness after the richness.

Impressions:

This Yamazaki 18 Years Old matured in American white oak is very much about richness and texture. The nose appears to show great maturity, with honey, spice, and a faint musky depth, while the palate is all about creaminess and viscosity. The flavours themselves are fairly straightforward, with tons of vanilla, cream and honey – with tons of sheer weight and decadent mouthfeel.

While not the most complex of the distillery samples, it has a clear role to play in adding a sense of depth and weight to the bigger picture of Yamazaki’s blending philosophy. As Andrew explained, this richness forms the base canvas and structure on which an older core expression like the Yamazaki 25 Years Old could be built upon.

Sample 4: Yamazaki Mizunara Oak 18 Years Old

Nose: Opens with sweet brown sugar, honey and golden syrup, layered over a more earthy impression of raw barley and a mild fired clay note. It feels deeper and more integrated compared to the younger Mizunara sample, with the earlier resinous quality pretty much rounded out

Palate: Light coconut and vanilla, with a strikingly delicate texture and refined. Golden syrup and coconut cream notes make a return, along with a very soft and supple body. Everything feels rather smooth, delicately sweet and understated. It is much less forceful than the 12 Years Old, and instead leans into restraint and subtlety with perhaps a nutty edge of sweet roasted coconut around the mid-palate section.

Finish: Medium in length, defined by a delicately lingering temple incense smokiness that is very soothing, quite unlike the brash assertiveness of Scottish peat. A lasting sense of calm spice and light sandalwood.

Impressions:

This Yamazaki 18 Years Old Mizunara Oak sample is a clear evolution from the 12. The palate is creamier and far more delicate in texture, showing how six additional years of maturation have mellowed the wood spice and resinous qualities into something very integrated and subtle. While the nose still carries familiar sweet and earthy tones of barley, sugar, and honey, the palate leans into elegance, with roasted coconut and cream giving a gentle richness without heaviness.

The most evocative moment is certainly the finish, where the Mizunara character fully reveals itself in the sandalwood-like incense note. Compared to the boldness of the 12 Years Old, this expression is more about refinement and restraint, showing how time really allows Mizunara to smooth out its rough edges.

Sample 5: Yamazaki Mizunara Oak 18 Years Old (Enhanced)

Note: This Yamazaki 18 Years Old Mizunara sample has been blended with a small portion of 25-year-old Mizunara.

Nose: Much more musky malt notes than the other samples of Yamazaki Mizunara, layered upon deep sweetness of honey and golden syrup once more. A delightful ripe persimmon note blends into the confectionary character of the aroma. Overall, this feels sweeter and richer, with a more distinctive malt and some fruitiness harmonising into the honeyed profile.

Palate: Very balanced and rounded, with a significantly thicker and richer texture. Sweet vanilla and toasted coconut cream set the tone. The wood character is far more layered here, and soft tannins provide structure while spice and deeper agarwood-like aromas emerge. Over time, the aromatic wood flavours slowly expand and evolve in depth, offering up notes of carved agarwood furniture, burnt sage and Chinese incense.

Finish: Long and aromatic, leaving behind rich temple incense. As the incense fades, there’s a faint mineral edge with a note of petrichor (the smell of rain)– truly evocative of visiting a Buddhist temple after rain– that adds a refreshing counterpoint to the wood’s richness. Toasted coconut notes extend well into the aftertaste of the final sip.

Impressions:

This special Yamazaki 18 Years Old Mizunara sample clearly demonstrates how a small addition of older 25-year-old stock can transform the profile. The nose impresses immediately with its sweetness and dried fruit depth, and the palate feels markedly richer than the standard 18, with temple incense aromas becoming prominent from the start. The mineral-petrichor character also adds a surprising dimension, keeping the richness from feeling heavy.

It's incredible to witness how just a modest share of 25-year-old Mizunara could make this so evocative, elegant and complete.

Final Thoughts & Yamazaki 25 Years Old Mizunara

Tasting through these Yamazaki component malts was an eye-opening journey into what makes Mizunara such an iconic, almost mythical element of Japanese whisky that transforms oak into an experience of place and memory. What stood out was how profoundly Mizunara-aged whisky evolves with time.

Mizunara demands patience, but it rewards it by giving Japanese whisky an identity unlike any other in the world. In its youth, it can be resinous, almost brash, with edges that feel woody and raw. By 12 years, however, it begins to reveal tropical flashes of coconut and pineapple. At 18 years, the wood mellows further into a subtle creaminess, carrying notes of roasted coconut and an unmistakable sandalwood-like incense that evokes Kyoto temples. With even older stock folded in, the oak becomes truly exotic, now really layered with agarwood, petrichor, minerality and fruit.

It is in this context that the newly launched Yamazaki 25 Year Old Mizunara Edition feels like a watershed moment. This is Yamazaki’s oldest malt that has been matured entirely in Mizunara oak. This is the culmination of decades of learning how to coax beauty from a notoriously difficult wood.

It's said that its aromas offer a sweetness of apricot compote, cacao latte-like smoothness, and spiciness of nutmeg and cardamom, along with a palate of bittersweet, spicy flavours with orange notes and nuances of cream, and finally a complex woodiness of Mizunara oak with bittersweet hints of oriental herbal medicine.

This expression is now available globally at a suggested retail price of US$7,500.

@CharsiuCharlie