If you're growing a particularly great heirloom tomato in your garden, chances are you will want to grow that tomato again, or maybe even share your tomato seeds with gardening friends and family. Saving tomato seeds is easy, but there is one step that you, as a new seed saver, may not know you should take. Make sure you isolate tomato flowers for true seeds.
Gardeners with large yards are at an advantage when saving tomato seeds because they can isolate tomato plants by placing them far enough apart from each other that they won't accidentally cross-pollinate and create seeds for a hybrid tomato. There is absolutely nothing wrong with hybrid tomatoes, but if you're growing an heirloom tomato, chances are you're doing so because of some unique characteristic to that particular tomato plant. Maybe it's the color, shape, taste or history behind the plant that calls you to grow it. Whatever your reasons, you are now a steward of the history of a tomato and you want to continue the line.
Small-space, and urban gardeners, like myself, don't have the luxury of being able to grow several tomato varieties and plant them far apart to keep the seeds true. Our cramped gardens may require us to either grow one heirloom tomato variety a year, or get creative and find a way to keep the blooms from being accidentally cross-pollinated by bees and other garden pollinators.
The same year I grew OSU Blue tomatoes I was growing other tomato varieties all on the porch garden. The porch garden is smaller than a jail cell so I needed a way to protect the OSU Blue tomato flowers from being cross-pollinated. Tomato flowers are self-fertile and unless you're really serious about ensuring your heirloom tomatoes remain true, you won't need this step. But if you want to be as close to 100% sure as possible that your heirloom strain is pure, you should isolate the blooms. Somehow I found myself with a number of teabags in my backpack after a camping trip and realized that the little bags were perfect for enveloping a tomato flower or two and protecting it. What you're creating is a little tomato flower chastity belt.
After you have isolated as many tomato flowers as you want. Give your tomato plant a good shake or two every morning for about a week. What you're doing is mimicking the vibrations caused by honeybees and bumblebees when they visit the blooms and dislodge the pollen that fertilizes each flower.
After a week you should see the little tomato fruit starting to form at each of the flowers. Don't forget to tie a string or plant tag around the tomato flower you isolated to help you remember which one was protected if you don't isolate each and every bloom on a tomato plant. Also, you want to place your tomato chastity belt on the flower(s) before it has a chance to open just to be on the safe side.
Seed savers have been saving tomato seeds for eons without going to lengths like this, but I do it because I know the disappointment that comes with growing a variety you're excited about only to discover that it accidentally crossed in someone's garden. I feel a moral obligation as a seed saver to try my best to ensure the tomato seeds I swap with other gardeners are true. If you're thinking of saving tomato seeds, isolate tomato flowers for true seeds.
Have you grown tomato seeds you got in a swap only to realize they were not as described? What's your favorite heirloom tomato seed to give to gardening friends?