Indeterminate. 80 days Heirloom Tomato Seeds. Many consider the San Marzano Heirloom Tomato to be THE plum tomato for making sauces. It has exceptionally good flavour. In some Italian towns it is said to be against the law to use any other variety for their pizza sauces. Ensure even watering and add eggshells to the soil for a bumper crop.