Barolo wine is produced from the nebbiolo grape variety with the Lampia, Michet and Rosé clones authorized. The clusters are dark blue and greyish with the abundant wax that dresses the grapes. Their form is lengthened, pyramidal, with small, spherical grapes with substantial peel. The leaves are of average size with three or five lobes. Compared to the annual growth cycle of other Piedmontese grape varieties, nebbiolo is one of the first varieties to bud and last varieties to ripen with harvest taking place in mid to late October. In some vintages, other Piedmontese producers are able to pick and complete fermentation of their Barbera and Dolcetto plantings before Barolo producers have even begun their harvest. According to DOCG regulations, Barolos are to be composed of 100% nebbiolo. Historically producers would blend other grapes such as a Barbera and today there is speculation that modern Barolo producers may be blending in Barbera, Cabernet Sauvignon, Merlot and Syrah but there has been no conclusive proof of this practice.(cn) In the 1990s producers in the Barolo zone petitioned that the required nebbiolo content be lowered from 100% to 90% but this petition was eventually defeated.