Cross Pollenation of Tomatoes

Tomato Flowers

• Tomato flowers are what produce the fruits, and where pollination takes place. Flowers contain the plant's reproductive system, including ovaries, stamens and pollen that work together to fertilize and form into fruit. Tomato flowers are small, about 1/4 to 1/2 inch, and yellow, with trumpet-shaped petals. A tomato plant with many yellow flowers will produce many tomatoes. The tomato plant requires full sun to grow well and produce flowers and fruit. Shade results in poor flower production affecting the number of tomatoes.

Hybrids and Heirlooms

• With thousands of different varieties of tomatoes, gardeners have a huge selection to grow. Heirloom varieties have been grown for at least 50 years, is open --pollinated and seed has been passed down through the years. Seeds from heirloom plants produce plants identical to the parent plants. Hybrid varieties have been cross-bred to create a new variety that has desirable traits from two parent plants. Seeds from hybrid tomatoes won't produce plants identical to the hybrid parent and may be sterile. Hybrid varieties are grown for their superior qualities such as disease resistance or larger harvests.

What Bees Do

• Bees, and the wind, as well as butterflies, moths, flies and other winged insects that are attracted to flowers touch the pollen inside the flowers. It clings to their bodies and legs and is transported to the next location the bees fly to and land. If that is another tomato flower, pollen from the first plant is transferred to the inner flower parts of the second plant, pollinating it and stimulating tomato, fruit, production. The wind blows pollen off of flowers and carries it through the air, moving it around, but is not as efficient at pollination as insects.

Growing Two Kinds of Tomatoes

• If you are growing two kinds of tomatoes in your garden, cross-pollination is only an issue if you want to save seeds to plant next season, especially if you are growing heirlooms that you want to preserve. If heirloom tomato flowers cross-pollinate, the seeds from the resulting tomatoes will not bear true to the parent plants' the following season. The tomato plants will grow and bear fruit, but the heirloom plant will not be preserved because a unique plant and fruit will develop from the genes of the two different parent plants. If you are serious about growing more than one kind of heirloom tomato and preserving them, you must cover flowers with very fine mesh bags before they open and manually pollinate opened flowers with a soft paintbrush. If you can plant the different varieties far apart, the likelihood of cross-pollination is much less, especially if there are physical barriers between the plants such as a high fence or tall growing plants like corn. Serious growers use small hoop houses to grow tomato varieties safely and prevent cross-pollination.