The grapevine is predisposed its genes to put all its strength into its descendants, the grapes, wich may be detrimental to the stock health. If there are too many grapes on the stock they may still become sweet enough to be eaten by birds to scatter the seeds. The vine itself may not have enough sugar (the sugar acts as an antifreeze in winter) to survive. One symptom of this problem is an insufficient lignification of the young shoots. If this is observed, some grapes should be removed and the remaining harvested early. Fewer grapes mean that the individual grapes are sweeter, and the stock is healthy - everybody gets something out of it!