Bordeaux Assemblage

Assemblage describes the process of combining separately-vinified lots into a final wine. It is not the same as field-blending (where multiple varieties are co-planted and harvested together) or co-fermentation (where varieties are crushed and fermented in the same vessel). In Bordeaux, the dominant tradition is to harvest each grape variety from each defined parcel at its individual ripening moment, ferment those grapes in separate vessels (typically stainless steel or concrete tanks for fermentation, then French oak barrels for malolactic and élevage), and then taste through the resulting lots in late winter or early spring to determine the final blend composition. This contrasts sharply with varietal winemaking traditions (Burgundy Pinot Noir, German Riesling, California single-variety Cabernet) where the wine is built around one grape and blending occurs only between parcels of the same variety.

• Assemblage = blending separately-vinified lots into a final wine; happens after fermentation and often after early malolactic conversion
• Distinct from field-blending (co-planted varieties harvested and pressed together) and co-fermentation (multiple varieties in same vessel)
• Each parcel of each variety is typically fermented separately at top châteaux, producing 30 to 60 distinct lots per vintage
• Bordeaux's tradition contrasts with Burgundy and other single-variety traditions; the multi-variety + multi-parcel structure is core to Bordeaux identity

Bordeaux AOC rules permit six red varieties: Cabernet Sauvignon, Merlot, Cabernet Franc, Petit Verdot, Malbec, and Carménère. In practice, Carménère survives in only a handful of estates (most was lost to phylloxera and confused with Merlot in 19th-century replantings). Each variety contributes distinct characteristics to the assemblage. Cabernet Sauvignon brings tannin, structure, blackcurrant fruit, and longevity. Merlot contributes plum and cherry fruit, supple texture, and roundness. Cabernet Franc adds aromatic lift, violet, and graphite minerality. Petit Verdot provides deep colour, peppery spice, and additional tannin support (usually 1 to 8 percent of a blend). Malbec adds dark fruit, body, and softness. In January 2021, four climate-adaptive varieties (Arinarnoa, Castets, Marselan, Touriga Nacional) were formally approved for experimental use in Bordeaux and Bordeaux Supérieur AOC blends, capped at 10 percent of the final blend.

• Cabernet Sauvignon: tannin, structure, blackcurrant, longevity; dominant on Left Bank gravels
• Merlot: plum, cherry, suppleness; dominant on Right Bank clay-limestone; most planted variety in Bordeaux overall (~60% of red plantings)
• Cabernet Franc: aromatic lift, violet, graphite; especially important on Right Bank cool sites (Cheval Blanc, Ausone, Lafleur)
• Petit Verdot: 1-8% of typical Left Bank blends; deep colour and peppery support; harder to ripen consistently
• Climate-adaptive varieties approved January 2021 for experimental use: Arinarnoa, Castets, Marselan, Touriga Nacional (capped at 10% of blend in Bordeaux/Bordeaux Supérieur AOC only)

The assemblage process unfolds over several months. After harvest in September and October, each parcel of each variety is fermented separately. By late winter or early spring, fermentation is complete and most lots have finished malolactic conversion. The technical director, winemaker, and consulting oenologists then taste through every lot, scoring each on its quality, intensity, balance, and compatibility with the château style. Trial blends are then constructed: typically a series of progressively more selective blends starting with broad inclusion and progressively excluding weaker lots. The first cut establishes which lots enter the grand vin pool. From that pool, the winemaker constructs the final grand vin blend, often blending and rebalancing variety proportions through dozens of trial blends over the course of two to four weeks. Lots not selected for the grand vin enter the second wine; lots not making the second wine enter the third wine (where one exists) or generic Bordeaux.

• Each parcel of each variety fermented separately (30-60 distinct lots typical at top châteaux); malolactic conversion typically complete by spring
• Tasting sessions led by technical director with consulting oenologists; lot-by-lot evaluation on quality, balance, style compatibility
• Trial blends progressively narrow the lot selection; typical process produces dozens of trial blends over two to four weeks
• Grand vin selection is the most exclusive cut; remaining lots go to second wine, third wine, or generic Bordeaux

Most major Bordeaux châteaux work with consulting oenologists during assemblage, with three names dominating the scene in recent decades. Michel Rolland, often called the most influential consultant in modern wine, has advised over 100 châteaux globally and his Right Bank style emphasises ripe fruit, polished tannins, and modern barrel régimes. Eric Boissenot, son of Jacques Boissenot who founded the family practice in the 1960s, is the dominant Left Bank consultant, advising Lafite Rothschild, Mouton-Rothschild, Latour, Pichon Comtesse, and many others. Stéphane Derenoncourt, working with both banks, is known for a more restrained style emphasising freshness and terroir transparency. Hubert de Boüard (of Château Angélus) consults extensively across Saint-Émilion. The consulting role is to advise on tasting, blending decisions, and stylistic direction; the final decisions rest with the château's technical director and ownership.

• Michel Rolland: 100+ châteaux globally; modern Right Bank style with ripe fruit and polished tannins; influential in establishing the New World 'international style'
• Eric Boissenot: dominant Left Bank consultant; advises Lafite Rothschild, Mouton-Rothschild, Latour, Pichon Comtesse, and many other classified estates
• Stéphane Derenoncourt: more restrained style emphasising freshness and terroir; consults both banks
• Hubert de Boüard: extensive Saint-Émilion consulting practice; also owns Château Angélus (resigned as PGCC-A reviewer following 2022 classification controversy)

Bordeaux's assemblage tradition has historically been a response to climate variability: the multi-variety system gives winemakers tools to compensate for differential ripening and to balance vintage-to-vintage variation. Climate change is now reshaping these dynamics. Warmer growing seasons have caused average alcohol levels to rise across the region (from 12 to 12.5 percent in the 1980s to 13.5 to 14 percent today), and the historical ripening gap between Merlot (early) and Cabernet Sauvignon (late) has narrowed. The 2021 approval of four climate-adaptive experimental varieties (Arinarnoa, Castets, Marselan, Touriga Nacional) reflects this concern: each variety is more heat-tolerant than the traditional Bordeaux varieties. The new varieties are capped at 10 percent of the final blend in Bordeaux and Bordeaux Supérieur AOC wines only (not in the named communal AOCs). The assemblage tradition itself remains the response: blending tools allow producers to balance the impact of climate-driven changes.

• Average alcohol levels have risen across Bordeaux from 12-12.5% in the 1980s to 13.5-14% today, reflecting warmer growing seasons
• The ripening gap between Merlot (early-ripening) and Cabernet Sauvignon (late-ripening) has narrowed under climate warming
• Four climate-adaptive varieties approved January 2021 for experimental use in Bordeaux and Bordeaux Supérieur AOC: Arinarnoa (Tannat × Cabernet Sauvignon), Castets, Marselan (Cabernet × Grenache), Touriga Nacional (Portuguese)
• Climate-adaptive varieties capped at 10% of the final blend; permitted only in Bordeaux and Bordeaux Supérieur AOC, not in the named communal AOCs (Pauillac, Margaux, etc.)