Nantes Coreless Carrot Seeds Heirloom Vegetable. Roots are a rich bright orange and average 15 cm (6″) in length and up to 4 cm (1.5″) in diameter. Consistently cylindrical, smooth skinned and blunt ended, Nantes is a great tasting, tender but crisp, almost coreless carrot…even when the carrots are harvested late in the season!