3309 C is a Vitis riparia x V. rupestris hybrid bred by Georges Couderc in 1881 and used as a rootstock. It is fairly vigorous and promotes earlier ripening. Dr Richard Smart (2015, p628) describes how Monsieur Couderc planted 18 seeds in a row of the nursery where he had added lime. Of the five which did not show chlorosis, 3309 C became the most successful. Dr Smart says 3309 C has high phylloxera tolerance and medium lime tolerance [3309C is not widely used in Champagne], and that 3309 C is better suited to humid than drought-prone soils [but does not like wet feet] adding that as rooting and grafting are easy use of this rootstock is widespread.
Some see 3309C as a universal cool climate rootstock. 3309C is Bordeaux’s most widely used rootstock. Only moderately more vigorous than Riparia Gloire, 3309 Couderc accentuates the early ripening profile of both Merlot and Sauvignon Blanc.
Dr Richard Smart in the Oxford Companion to Wine 4th edition ed. Jancis Robinson MW and Julia Harding MW (Oxford University Press, 2015, p628.