F1 hybrids, which are largely annual and vegetable cultivars, are produced by crossing two stable seed lines (called inbred lines) that give rise to especially uniform progeny that possess good vigour, yield and other properties. Tomato ‘Cristal’ F1 and sunflower ‘Harlequin’ F1 are examples of F1 hybrids. It will say on the seed packet if the variety is F1