Petit Verdot
Petit Verdot is a variety of red wine grape, principally used in classic Bordeaux blends. It ripens much later than the other varieties in Bordeaux, often too late, so it fell out of favour in its home region. When it does ripen it adds tannin, colour and flavour, in small amounts, to the blend. Petit verdot has attracted attention among winemakers in the New World, where it ripens more reliably and has been made into single varietal wine. It is also useful in 'stiffening' the mid palate of Cabernet Sauvignon blends.
When young its aromas have been likened to banana and pencil shavings. Strong tones of violet and leather develop as it matures.
History
Petit Verdot probably predates Cabernet Sauvignon in Bordeaux, but its origins are unclear. There are records of it in the eighteenth century, but its characteristics suggest an origin in much hotter climes than the Gironde.
It is one parent of Tressot, the other parent being Duras, a grape from the upper Tarn valley near Toulouse. It's possible that both were brought to the region by the Romans as they moved inland from the Mediterranean.