Use Bagging to Prevent Cross-Pollination in Vegetables

One of the most valuable things open-pollinated and heirloom vegetables offer gardeners is the ability to save seed that will breed true to the parent plant. However, many times the home garden houses different varieties of the same species – or members of the same vegetable family which are capable of cross-pollinating.

The problem with vegetable varieties cross-pollinating is that the seed is no longer pure as far as the variety is concerned. When varieties cross, they create a hybrid plant. Vegetables will certainly grow if the seeds are planted, but the gardener won’t necessarily know what the hybrid plant will produce.

In a home garden environment, it may be impossible to be sure that varieties are kept far enough away from each other to be certain that pollination has been pure. Physical barriers or mechanical isolation are one of the best ways to keep plants from cross-pollinating and one of those physical barriers is called “bagging”. Caging and hand-pollination are also used for this purpose.

The Bagging Technique

Plants that are insect-pollinated such as broccoli, cucumbers, watermelon, and pumpkins can be protected from cross-pollination by using the bagging technique. It also works well for self-pollinating plants such a tomatoes and peppers.

Bagging is exactly what it sounds like; covering the female flower with a bag so that pollinators can’t pollinate it. In this case, you would hand-pollinate the female flower using either the paintbrush or flower-to-flower technique. Then the flower should be covered with a paper or light material bag like muslin or a commercial product called Reemay. Don’t use plastic bags for bagging flower heads as they can cause the flower to fry as well as get slimy and are therefore unsuitable for seed production.

For veggies that self-pollinate, cover the blossoms with a bag as soon as they appear. You’ll need to secure the bag to the stem without hurting the plant. You can use a cotton ball under the edge of the bag and then tie it with thick thread or a twist-tie. You want the tie to be secure, but do this gently.

The cotton ball will also thwart determined bugs from reaching the flower. When you see fruits forming, you can take the bag off with no further worries. Remember to tie an identifying string or ribbon onto the stem after the flower has set fruit before you remove the bag! This way there’ll be no question about which flower you pollinated.

Using physical barriers such as bagging doesn’t take much time to perfect and in the end, you’ll have pure pollinated seed to save for your personal seed bank and next year’s garden.

For more information on pollination and open-pollinated plants, check out Use Caging to Prevent Cross-Pollination Between Vegetables, Hand-Pollinate Cucumbers, Pumpkins, and Squash, and The Definition of Heirloom Vegetables.