John recognised the potential of Margaret River for high-quality grape-growing before a single vine was planted, and is the pre-eminent interpreter and recorder of the climate of all Australia’s wine regions. He has also divided climate into four categories: hot, warm, moderate (or temperate, only a linguistic difference), and cool. He records the mean January temperature, biologically effective degree days, altitude, sunshine hours per day and rainfall for the seven-month growing season.
In so doing he has collected research dating back to Swiss botanist A. P. de Candolle, who in 1855 showed that active growth in the annual cycle of budburst to harvest ceased as long as the temperature was less than 10˚C. One hundred years later, the American researchers Amerine and Winkler propounded a detailed summation of five temperature groups from very cool to hot. Australian research by Peter Dry and Richard Smart significantly refined the Amerine and Winkler system, and from 1965 through to the present, Gladstones has taken the broader issues of climate (including climate change) onto another level altogether.
An so to Australia and its most important variety, shiraz, which is grown in every region, its 418,000 tonnes harvested in 2019 a tad under a quarter of the total crush of 1,729,000 tonnes.
This newsletter covers shiraz grown in regions with a mean January temperature between 23˚C and 25.9˚C, which is hot, the foremost in quality and reputation Brokenwood, and close behind Mount Pleasant and Tyrrell’s of the Hunter Valley. These wineries break all the rules, as most of their best shiraz wines are medium-bodied (not full-bodied) and 14% or less alcohol (not 15% or more), the result elegant wines of finesse.The Swan Valley and Rutherglen are two other hot regions growing and making full-bodied shiraz, with the alcohol typically 15% or more. In these regions, the best are polished and balanced, but they have little finesse.
In the next newsletter, I will cover warm climate shiraz.