3309 (Vitis riparia x Vitis rupestris)

Has very low tolerance of limestone (CaCO3); it will tolerate only up to 11% 'active' limestone (i.e. the limestone part of the soil which the vine can take up; this is very dependent on the composition and structure of the soil). Excess active limestone generally has a detrimental effect on growth and causes chlorosis (a physiological ailment, due to various causes, resulting in yellowing of leaves and other green parts of the plant).
Strength of growth is medium to weak, much less vigorous than SO4. It is particularly good for closely planted vines. It advances the vegetative cycle and has good reliable fruit-set. It is popular in France, the French always ask why 3309 is not used in England, they think it would be very good in most circumstances; however, if the soil pH is above 7.3 then it is not suitable.

www.winegrowers.info