Nantes Organic Carrot Seeds Heirloom Vegetable. This is the variety made famous by market gardeners. Nicely shaped cylindrical roots about 17 cm (7″) long are blunt ended, sweet and crunchy with almost no core. For those looking for a fast crop, Nantes matures relatively early in the summer. Due to its smooth textured skin, Nantes is an easy carrot to clean.