Thanks to the fashion for Japanese whisky, mizunara oak is highly in demand all over the world. But what makes it different from European or American oak? And is it a suitable material to make casks from anyway? Ian Buxton investigates.

Why would you make casks from a tree that takes more than 200 years to grow to a sufficient size? Which is already highly demanded by makers of luxury furniture and thus more expensive than the alternatives? And which is ill-suited to making barrels anyway, being difficult to shape into staves and prone to leakage?

Tasting barrels of whisky at Yamazaki in Japan

Photo courtesy of Yamazaki

Water oak

Even the name might put you off. Mizunara comes from the Japanese mizu, meaning water and nara, meaning oak. In Latin it’s known as quercus crispula. You’d imagine that coopers and distillers would take the hint. But no, mizunara casks are the hottest name in wood and, splashed across a whisky’s label, almost a guarantee of a premium price and a rapid rate of sale. Some, in fact, are so keenly sought after that they become the subject of a lottery.

So what makes this timber quite so desirable? Is it, in fact, Japan’s secret weapon in the world whisky wars? It’s all about the taste, of course, the best mizunara casks offering the distiller delicate hints of sandalwood, agarwood, rich coconut, and a marked fruity note that characterizes the finest Japanese whiskies. The unique sweet and spicy flavour is apparently thanks to – science alert – the oak’s high level of lactones.

Rumour has it, though, that the use of Mizunara oak for whisky casks was an accident of history and due more to the lack of availability of other barrels due to import restrictions into Japan following the second world war than to any recognition of the native wood’s distinctive qualities. Time was also a critical factor. Extended aging of whisky is a relatively recent phenomenon but it appears that it takes time – some commentators maintain as long as fifteen to twenty years is required – for the initially more forceful mizunara wood impacts to dissipate and the full benefit be obtained. In a market where most whiskies were destined for, by today’s standards, rather youthful blends this was a problem.

Scottish distillers take an interest

Thus, with Japanese whisky rather looked down on in world markets until recently, it took the award-winning progress of Yamazaki in important international competitions to draw the attention of the larger global industry.

But even though Western whisky distillers came to appreciate mizunara’s unique qualities they still faced the problem that the wood was difficult to work and casks near impossible to source. So initially, to find sufficient casks, significant resources were needed which explains why early Scotch whisky releases such as Chivas Regal Mizunara and Bowmore came from companies with financial muscle and Japanese connections.

Yamazaki Mizunara 18

Yamazaki Mizunara 18 year old. If you have to ask the price, you can’t afford it

A unique flavour

Now smaller companies are getting in on the act. Kaiyo is a small Japanese blender specializing in mizunara-matured whiskies and they claim to have discovered an interesting shortcut to reduce the aging necessary for the full flavour impact. 

According to the company’s Jeffrey Karlovitch, while conventional American and European oak are at their best during the first fill, mizunara improves with time. “The second and third use: that’s where the magic really happens,” he says.

Another example from Japan comes from the Kurayoshi Distillery with their Matsui Mizunara Cask – the lack of an age statement suggesting finishing to me. Mind you, there’s something clearly different about Kurayoshi, whose website claims that “Kurayoshi’s water is soft and it has a condensed taste”. Condensed water – definitely a whisky first!

Buyer beware

Like ‘Japanese whisky’ in general my final point is, as ever, caveat emptor. There is a danger that mizunara is falling into the hands of over-enthusiastic PR and marketing types, eager to associate their product with this magical, mysterious wood borrowing some of its mystique and brand allure without allowing it the time essential to work its undoubted magic.

So, look carefully at your planned purchase and expect to pay handsomely for the real thing.