Cabernet Franc is very closely related to cabernet sauvignon; it is widely presumed that cabernet franc is just a well established mutation. It is ideally suited to cooler climates, as it buds and ripens earlier than cabernet sauvignon. Additionally, it is less susceptible to poor weather during harvest. In the Medoc and Graves region of Bordeaux, where it typically constitutes about 15% of the final blend, it is seen as a measure of insurance against poor cabernet sauvignon or merlot weather. Cabernet franc used to be planted almost as widely as cabernet sauvignon in Bordeaux well into the 60s, but cabernet sauvignon had swung into such favor that 30 years later it had twice the acreage of cabernet franc.