F1 hybrid seed production involves the crossing of two different inbred lines. Either line can be the female or male parent, but normally the best seed yielder is selected as the female parent.

Both parents should be pure, preferably being self-pollinated for more than 6 generations (this is called inbreeding). Parents are selected for their desirable traits (high yields, disease resistance, fruit quality, earliness, etc.).

It is important to have plenty of pollen available for making hybrid crosses. Since tomato vines bloom profusely, a ratio of 1 male for every 4 female plants is recommended.

Seeds of male plants are sown 3 weeks earlier to ensure that pollen is available from the beginning of breeding operations.