San Marzano Organic Tomato Seeds 4201 Heirloom Vegetable. This classic Italian plum tomato is ideal for making sauce and canning. Large bright red fruits with few seeds and slightly flattened sides average 150 g (6 oz) in weight. The skin is quite crack resistant while the flesh is both meaty and mild. Indeterminate growth pattern (individual fruits ripen successively over many days).