Apr 25, 2019 05:06PM
By Patrick McGee
Why wait for the bees? Hand-pollination can help home gardeners take their tomato harvests to the next level with crossbred varieties and bountiful yields.
John Porter, Urban Agriculture Program Coordinator at the University of Nebraska-Lincoln Extension and College of Agriculture, says it’s an easy and straightforward process. He encourages gardeners to give it a try.
Hand-pollination can increase yields in the absence of conditions required to make plants produce.
Pollination and Seeds
In order for a tomato plant to create tomatoes, it must be pollinated. Seeds also come from pollinated tomatoes. When left alone, tomatoes will self-pollinate with help from insects and the wind.
An heirloom tomato will produce seeds similar to the parent plant because of self-pollination. A hybrid “cultivar” requires starting with a specific male and female plant; however, it is possible to cross any tomato varieties because all tomato plants belong to the same species.
Gardeners may cross many varieties and then grow out the results. Then, they can pick and choose which varieties to save for later planting. Each plant will be at least a little bit different.
“Cross a red slicing [tomato] and a yellow cherry [tomato], some seeds should end up with different traits from each parent,” Porter says.
Tomato flowers are enclosed reproductive systems, meaning that the stamens (the male part) and the pistils (the female part) are totally enclosed. As a result, Porter says, tomatoes don’t cross-pollinate very easily.
The pistil will usually be the center part of the flower. It is larger and can have multiple sections on it. There are usually multiple stamens arranged around the pistil.
“Stamens are a threadlike filament with [what resembles] a pinhead on the top—that’s where the pollen comes from,” Porter says. Pollen is the yellowish powder present in flowers.
Different tomato varieties planted next to one another will not likely cross-pollinate, he says. A natural hybrid is therefore unlikely.
The Hand-Pollination Process
Porter says breeding tomatoes is a straightforward process: “Basically, you just need to take the pollen from one flower and pollinate the other one with it. Pick a mother and father plant. You want to take the pollen from the father plant.”
The next step is to open up the enclosed flower to pollinate. Remove the flower from the father plant and use it (or a tiny paintbrush) to pollinate the open flower. Porter suggests removing the father plant’s flower because opening it up will damage the sheath that covers the stamens. “It will be damaged anyway,” he says.
Selecting a good candidate female flower is important. “You’ll want to get it right when it opens up, or a little beforehand, right as it matures,” he says. “At that time, open it up so you can get into the reproductive structure. Remove the male structure, the stamen, so it does not self-pollinate. This is important.”
Then, put pollen from the designated male plant onto the stamen of a flower on the designated female plant. “You want to do this process a few days before the flower really opens—just to reduce the chances of self-pollination,” Porter says.
Finally, to effectively cross-pollinate, the flower must be isolated after hand-pollination. Porter says small paper bags or fine mesh bags will work. “You just want to seal off that flower so bees or foreign pollen doesn’t pollinate it,” he says.
Every flower in the tomato plant that is hand-pollinated will produce hybrid fruit and hybrid seeds. Each of the hand-pollinated flowers must be protected to avoid cross-pollination.
The Mystery of Reproduction
Although insects (such as bees) and the wind normally assist in tomato plants’ self-pollination, Porter says that hand-pollination may be essential for gardeners working in conditions isolated from the natural elements. This may be true of tomatoes growing indoors or in pots on a porch.
Rainy weather and excessive heat can also reduce the activity of pollinators. Such conditions further warrant hand-pollination by gardeners.
Studies have shown that, in the absence of wind, a fan can significantly increase yield as well. Greenhouse workers sometimes use stingless bees. But hand-pollination will do the trick just as well.
Beyond producing unique fruits of the gardener’s own selection, hand-pollination can teach children about natural reproduction.
It is a good reminder that in our world of big-box stores and industrial agriculture, our food is not just a commodity—it is alive, complex, and worthy of our respect and admiration.
Visit extension.unl.edu for more information.This article was printed in the May 2019 edition of OmahaHome. To receive the magazine, click here to subscribe.