In Bordeaux they will tell you that Merlot is the perfect partner for Cabernet Sauvignon, because the Cabernet doesn’t always ripen reliably on the left bank, and the fleshier tones of Merlot complement it by filling in the mid palate. In Napa they will tell you that Cabernet Sauvignon ripens so fully and reliably here that there is no need for Merlot; it makes a complete wine in itself. In Chile they used to follow the Bordeaux model by blending the Cabernet Sauvignon with Merlot; but then it turned out that most of the Merlot wasn’t Merlot, it was really Carmenere; they did not throw up their hands with horror, tear out the Carmenere and replace it with real Merlot; now instead they make a point of producing varietal Carmenere or of blending it with Cabernet Sauvignon. In Argentina, if they blend Cabernet Sauvignon, it’s usually with Malbec, which is the predominant black variety. In nineteenth century Bordeaux, Cabernet Sauvignon was usually blended  with Malbec and Carmenere as well as Cabernet Franc: the Malbec was replaced by Merlot, and the Carmenere disappeared after phylloxera struck. The blend everywhere is as much a matter of historical accident as a deliberate search for what varieties best complement one another. So the question is whether Cabernet Sauvignon still needs to be blended, given that the climate is warmer  in Bordeaux than it used to be, and that the other areas where it is planted are mostly warmer than Bordeaux anyway.  And if it does need to be blended, what other varieti(es) really give the best complexity, and are they necessarily the same in every region.

Even though Bordeaux has experienced warmer temperatures in the past decade, tastings of barrel samples have convinced me that the Cabernet Sauvignon makes a more interesting wine when it is blended. As a single varietal wine, it tends to have very pure, precise, but more linear flavors: it broadens out to become more interesting when blended. I believe the same is actually true in Napa, but not for the conventional reason. Young Napa Cabernets can be so bursting with fruit that you really do not see any need for any other variety to round out and complete the flavor profile. But wait a few years. As those primary fruits drop out, the wine begins to become more linear, more austere, the bare bones of Cabernet show more clearly, and you feel that by ten years of age it would very often be improved by some Merlot, which brings more interesting savory development.

A recent visit to Chile left me wondering about the rationale for blending Cabernet Sauvignon with Carmenere. If you think you have difficulties ripening Cabernet Sauvignon, try Carmenere – which usually harvests about one month after the Cabernet Sauvignon. That alone shows you why it became untenable in Bordeaux. Even in Chile, where the Cabernet ripens quite reliably, Carmenere can be questionable; it needs to be grown in the warmer sites. When it ripens fully, it develops a smooth, elegant palate, with tannins that seem more supple than Cabernet Sauvignon, and it brings elegance to a blend. When it does not ripen successfully, it has something of the same herbaceousness as Cabernet Sauvignon itself, so it’s something of a double or quits game.

Malbec is somewhere between Merlot and Cabernet Sauvignon: not as fleshy as Merlot, but certainly smoother and more supple than Cabernet Sauvignon. Under peak conditions, Malbec may be a more interesting blending partner for Cabernet Sauvignon than Merlot, because the tannic structure is complementary: the more supple character of Malbec adds smoothness to the tighter structure of Cabernet Sauvignon. It doesn’t fill in on the mid palate in quite the same way, so the wine tends more to elegance than fruit-driven power.

For roughly a hundred years, from its rise following the phylloxera problem in the 1880s until a couple of decades ago, Merlot was the perfect blending partner for Cabernet Sauvignon. This is not true in the warmer climates of Napa and Chile, where the “Merlot collapse problem” describes the situation in which Merlot goes straight from green, herbaceous character to over-ripe jammy character, with too narrow a chance to catch it at the right point. I sometimes wonder whether Napa’s concentration on varietal Cabernet Sauvignon isn’t due as much to their difficulties with Merlot as to the attractions of the Cabernet. I am inclined to wonder whether Syrah would be a good choice, since it has richer tannins than Cabernet and can add a touch of aromatics that increases complexity, but Napa seems fixated on a bimodal view: it’s either Cabernet or it’s a Bordeaux blend. Syrah  might also do well in Argentina and Chile, but the accidents of history mean that Malbec and Carmenere are well entrenched. Come to that, it may be time for Bordeaux to reconsider, because in the 2009 and 2010 vintages, the Merlot became so ripe and alcoholic that in many cases it was impossible to blend it into the Grand Vin and it was relegated to the second wine. (An amusing paradox here, since that can make the second wine higher in alcohol than the Grand Vin, and the concept that higher alcohol goes with wines at higher appellation levels is well entrenched in the French hierarchy.) How about going back to Malbec or Carmenere in the Medoc – or maybe Syrah.