How Far Apart Should Tomato Plants Be Planted to Prevent Cross Pollination?

Tomato Vines with Ripe Fruit

Separation of flowers by distance is common to prevent cross pollination and thus, the creation of hybrid seeds. Cross pollination has no effect on the fruit grown on the plant that is cross pollinated, it only affects the seeds for the next generation.

Self Pollination

The flowers of true tomatoes are somewhat malformed and most tomato flowers self pollinate themselves as they mature. Cross pollination, therefore, is fairly rare between different varieties of tomatoes. In order to create hybrids, seed companies deliberately remove a portion of the flower to be cross pollinated. It is possible however, for certain bees to cross pollinate tomatoes if the bees visit the plants at the right time. Serious seed savers should take care to isolate plants or fruits from which they plan to save seed.

Commercial Isolation

Commercial growers should separate plants by a minimum of 400 feet to prevent cross pollination with one exception: currant tomatoes must be separated from other varieties by at least 1/4 mile. Currant tomato flowers are not malformed like other varieties and cross pollinate very easily. Additionally, this separation distance should be maintained even if the currant tomato plants are kept enclosed within a barrier such as a screened box or cage.

Garden Isolation

Saving seeds at home is fun and thrifty. Separate individual plants and rows by 5 feet. Although it is possible you might get a cross pollinated tomato or two, the consequences are a hybrid variety the following year that you were not expecting. Save seeds from a number of tomatoes from different plants in order to minimize any problems. The relative rarity with which tomatoes cross pollinate naturally is such that for home gardeners, distance isolation is rarely required. However, to ensure your seed strains remain pure, select seeds from more than one plant and always keep the past three to five years of seed selections.

Blossom Isolation

Isolate blossoms by enclosing the vine ends in a white paper bag just as the flowers begin to show. Put the vine branch into the bag and close it with a wire tie. After the other blossoms on the plant begin to grow into tomatoes, remove the bag but label the branch. Select only those tomatoes that grew from flowers that were inside the paper bag, for saving seeds. This method of isolation works well when distance isolation is impossible.

Plant Isolation

Another method of isolation is to enclose the plant in a cage made of window screen. The cage must be big enough to enclose the plant, allow it room to grow and provide support for the plant. While the plant is producing flowers, the cage must not be opened lest a pollinator accidentally gains access and cross pollinates the flowers. If you are saving seeds commercially from an entire plant, this method combined with distance isolation is preferred over the others as all the fruit from the plant will have self pollinated seeds.

References

• "100 Heirloom Tomatoes for the American Garden;" Dr. Carolyn Male PhD; 1999

Resources

• Tomato Seed Saving