A Natural Home for Cabernets, Merlot and Shiraz

The heat summations of Bordeaux on the Atlantic Ocean in the south west of France, the home of Cabernet Sauvignon, Merlot and Cabernet Franc, and Hermitage on the Northern Rhone in France, the home of Shiraz, are nearly identical and warmer than either Coonawarra or Whalebone Vineyard through the growing season.

Being close to the ocean, Bordeaux has warm nights and moderate days which measured as the average difference between the night-time minimum and the daytime maximum temperatures over the growing season is 8.4ºC (diurnal range), whereas Hermitage has cold nights and hot days and has a diurnal range of 12.8ºC. Typically the Bordeaux climate is described as “maritime” and suits Cabernet Sauvignon, Merlot and Cabernet Franc. Hermitage is described as "continental" and is suited to Shiraz. Unusually, even though they are close to the coast of the Great Southern Ocean, both Coonawarra and Whalebone Vineyard have large diurnal ranges, Coonawarra 14.1ºC and Whalebone Vineyard (Struan) 14.8ºC. Being continental and similar to Hermitage, ostensibly Coonawarra and Whalebone Vineyard should be better suited to Shiraz than Cabernet Sauvignon.

Because of their relatively low heat summations compared to Bordeaux and Hermitage it might be concluded that Coonawarra and Whalebone Vineyard are marginal terroirs for the full ripening of Cabernet Sauvignon and Shiraz and especially Cabernet which has a greater heat requirement than Shiraz.

Both Coonawarra and Whalebone Vineyard are capable of ripening both varieties to full and opulent maturity because April is warm and dry and usually allows fruit to remain on the vine to achieve optimum ripeness, whereas October in Bordeaux and Hermitage is much cooler and wetter and the harvest window is much shorter.

Finally Struan and Whalebone Vineyard have much lower wind speeds during the growing season than Coonawarra and I am convinced this above all factors allows Whalebone Vineyard to ripen both Cabernet Sauvignon and Shiraz earlier and to a slightly more opulent style and this applies especially to Shiraz. Whalebone Vineyard in particular and Wrattonbully in general are peculiarly suited to the production of Cabernet Shiraz blends, an Australian traditional blend and once common in France when the practice of "Hermitaging" was used to bolster the wines of Bordeaux in deficient years.