Plant breeding isn’t just for commercial growers. With some knowledge, a bit of effort and a fair amount of patience, any home gardener can breed new crosses of flowers or vegetables. To discuss how to create hybrid and open-pollinated plant varieties, my guest this week is garden writer and plant breeder Joseph Tychonievich.
Joseph is a life-long lover of plants and gardening who earned a bachelor’s degree in horticulture from Ohio State University. He went on to work for specialty rare plant nurseries in Japan and Michigan before pursuing writing full-time. He’s lived in many places, moving most recently from Virginia to South Bend, Indiana. He is a contributor to Fine Gardening and other gardening magazines and is the editor of the North American Rock Garden Society quarterly journal. Joseph is the author of “Plant Breeding for the Home Gardener,” “Rock Gardening: Reimagining a Classic Style” and“The Comic Book Guide to Growing Food,” plus he hosts the “What’s Going on in the Garden?” podcast.
Though Joseph has loved gardening from the time he was little, his parents were not gardeners themselves, so he is not quite sure where that love comes from. He has always enjoyed growing plants from seed and watching them develop. His mother recalls he asked for plants and seeds for his 5th birthday.
Joseph became intrigued by plant breeding one year when he grew violas and pansies from seed. “They are really inclined to self-sow, and the bees like to make hybrids,” he says. “So I’d grown a bunch of them, and then the next year, the self-sown seedlings were all interesting hybrids that the bees had made between my different varieties in the garden, and I was just fascinated by the diversity that was popping up.”
Joseph had started with just a few varieties but all sorts of colors and shapes were popping up. The violas and pansies self-sowed aggressively in the absence of mulch. He knew he had to thin the flower patch, so he kept the ones he liked the best and rogued the rest. After repeating this process for a few years, his violas and pansies looked nothing like what he has started with. Because he narrowed down the flowers to his favorites year after year, they had become customized in the colors, shapes and sizes that he preferred.
While people think plant breeding is complex and involved — which it can be — it can also be as simple as letting flowers self-sow and keeping the ones you like best, Joseph says. Removing the least desirable flowers takes them out of the cross-pollination equation, so only the most desirable proliferate.
Joseph points out that seed savers are plant breeders, whether they think they are or not. That’s because anytime they thin seedlings until the most vigorous are left, they are breeding better plants.
One of Joseph’s early loves in the garden was roses, from the time he was a teenager. When he was 14, he found the Rose Hybridizers Association’s online forum for “hardcore rose breeding nerds,” he recalls. The breeders he met online were generous with their knowledge and their rose cuttings.
Rose breeding is on another level compared to breeding self-sowing plants, but Joseph says the basics don’t change that much. Plant breeding, for the most part, comes down to making a bunch of hybrids, growing a lot of seedlings, and picking out the ones you like best. Commercial and university plant breeders do this on a massive scale, growing out tens of thousands of seedlings, but it’s the same principle as what home gardeners do.
Joseph still has his first-ever intentional hybrid: a cross between a Rosa rugosa hybrid and the native swamp rose, Rosa palustris. He’s moved many times since making that cross but he always brings cuttings with him and continues to breed roses using that hybrid.
Joseph’s interest lies in making plants less work. He wants to create roses that are disease-resistant and don’t require staking. Another long-term project has been breeding fully winter-hardy gladiolus with stronger, shorter stems that don’t need to be staked.
Trade-Offs While Breeding Flowers
While breeding flowers, some traits are lost while others are gained. For example, while breeders seek longer-lasting blooms, the hybrids may lose their fragrance.
Fragrant flowers don’t last as long as less-fragrant flowers, Joseph notes. “The same hormone that drives a flower fading also drives fragrance production.”
Heirloom carnations are incredibly fragrant. Fragrance production is driven by a gas that plants produce called ethylene, which is sometimes called the “death hormone” or “ripening hormone.” Ethylene is the reason you don’t put bananas in a sealed bag, Joseph explains. Ripening bananas naturally produce ethylene, and if the gas is trapped in a bag, it will cause the bananas to ripen too rapidly. Ethylene also causes flowers to fade and turn brown.
Modern, hybrid carnations can last for a really long time and be shipped from continent to continent because ethylene production has been bred out of them. The downside is they produce no fragrance. (Chemical sprays can also be used to knock out ethylene production in bouquets or fruit to extend their life.)
Breeding for long vase life reduces fragrance in most types of flowers, not just carnations, and it’s not always clear why. “Sometimes traits can be connected in ways we don’t see,” Joseph notes.
Plant breeding is a matter of making choices and trade-offs. For example, the seedling with the biggest flower is unlikely to also be the seedling with the greatest disease resistance. Joseph likens it to house hunting: If you are searching for the house with the biggest yard, you won’t find it in the best location. “The more different things you’re trying to find the harder it is to find something that has everything,” he says.
Envisioning a New Variety
If you want to dive into plant breeding, it’s always fun to start with a plant you love growing. Once you have picked a subject, set the goal for your breeding project. Do you wish that plant was more fragrant? Sturdier? Choose your priority.
Often, you can find an existing variety that has some of the traits you want, but not all, such as a fragrant rose that is not disease resistant or a short gladiolus that doesn’t have colorful flowers.
Find plants that each have a trait that you want, and hybridize those plants together. “That allows you to shuffle up the traits of those two parents and get all kinds of new diversity to start exploring with,” Joseph says.
He has a thing for weeds so he set out to breed a desirable broadleaf plantain (Plantago major). It’s a hybrid called Purple Perversion, with frilly leaves and plum color.
How to Cross-Pollinate Plants
Flowers are the sex organs of plants. The male parts are the anthers, which are found in a ring around the center of a flower. The anthers contain pollen. The female part of the flower is found at the center and is called the pistil. The tip of the pistil is the stigma, which receives pollen.
Collecting pollen starts with picking apart a flower to find the anthers. Next, take that pollen and apply it to the stigma of another flower. That second flower will produce seeds that are a mix of both parent flowers.
Instead of pollinating manually, you can allow bees and other pollinators to make crosses for you at random. Columbines readily hybridize this way, and so do hollyhocks, Joseph says.
However, if you are making deliberate crosses, you will need to keep bees out of the flowers. If working with big flowers like squash blossoms, you can tape the buds shut before they open, and after hand-pollinating the blossoms, close the petals back up. For smaller flowers, nylon mesh bags can be wrapped over the buds. You can find nylon mesh bags sold for fruit protection or as party favor bags. Another option is to buy tulle from a fabric store and cut it into the size you need to wrap a flower.
“Usually when the flower is open and looking showy, that’s when they’re signaling pollinators to come in, and so that’s the right time for you, the human pollinator, to come in and make your crosses,” Joseph says.
Keep in mind that hybridizing only affects the seed that a flower produces and not the fruit. For example, if you pollinate the flowers on a cherry tomato plant with pollen from a beefsteak tomato flower, you’ll still get cherry tomatoes. It’s the seeds inside those cherry tomatoes that will contain a mix of cherry tomato genetics and beefsteak tomato genetics. You’ll need to plant those seeds to get fruit that are cherry and beefsteak hybrids.
Manually Pollinating Self-Pollinating Flowers
Some flowers have both male and female parts and can self-pollinate. When you plan to make a cross of plants with self-pollinating flowers, keeping bees out is not enough. You’ll need to remove the male parts.
To emasculate a flower, go in before it has completely opened on its own and remove the anthers. The flower with the anthers removed will be the female parent of the hybrid.
Lettuce readily self-pollinates and is hard to make crosses with. Tomatoes self-pollinate easily but are easy to cross. Peppers can self-pollinate but are less likely to than tomatoes. Squash have separate male and female flowers, so it’s impossible for them to self-pollinate.
Corn Is an Exception
Cross-pollinated corn behaves differently than other vegetables. Joseph explains that the color of each kernel on an ear of corn is determined by the genetics of that seed and not just the parent plant. So if you take a white variety of corn and pollinate it with blue corn, the kernels will be blue.
Multicolor corns like glass gem corn are grown in a population that is genetically diverse. Each ear has many different colors because it is pollinated by many different corn plants.
If you have an ear of corn with kernels of various colors, you can pick out all the kernels of a certain color, plant them, and they will produce that color in subsequent generations.
From First-Generation Hybrids to Stable Seeds
Seeds saved from a new cross are first-generation hybrids, known as F1 hybrids. “The first generation hybrid has exactly half its genes from one parent and exactly half its genes from another,” Joseph says.
If you started with two open-pollinated parents that both grow “true to seed,” the F1 hybrids will all look fairly identical. For example, an heirloom Brandywine tomato and a Matt’s Wild Cherry will produce hybrids with fruit that are all roughly the same size and the dominant traits will show through, Joseph says. “Then if you save seeds from your first-generation hybrids, the next generation is when all hell breaks loose — in a good way. That’s when all the traits of the two original parents get reshuffled in new combinations.” Size, shape and color become unpredictable. “That’s when you get to have fun, really picking out the ones that you like best.”
Once you pick out the tomatoes you like best — the ideal size, the best flavor, the most vigor — you will need to breed them for a few more generations to stabilize them. In each subsequent generation, by saving seeds from the fruit you liked best, you will cut the variability down by half. Eventually, around the fifth or sixth generation, you’ll get the predictability and uniformity that growers and seed sellers desire.
Variability can be fun, especially with flowers. For example, Joseph grows petunias that he has hybridized but made no effort to stabilize because he enjoys the different colors.
Annual flowers and vegetables can be bred much faster than slow-maturing trees like apples. When growing an apple tree from seed, keep in mind that it will be years before the tree fruits and produces a new generation of seed.
Plants that are propagated from cuttings or grafting don’t require multiple generations to stabilize. Once you make a plant that you like, you can keep cloning it from cuttings. Those cuttings will be genetically identical to the original.
Propagating by cuttings is how roses are produced. You can also propagate tomato plants and pepper plants from cuttings, but you’ll need a heated greenhouse to keep those plants alive all winter.
Home Plant Breeding Vs. Commercial Plant Breeding
Commercial plant breeders have more considerations than home plant breeders do.
Commercial breeders need a plant to perform well everywhere from Maine to Arizona to California, while a home gardener only needs a plant to perform well in one place. Commercials breeders also need plants to grow quickly and to be resistant to damage while shipping to stores. Home gardeners don’t need to select plants for those traits. Commercial growers need flowers of five different colors to all bloom at the same time for marketability, while home gardeners don’t care if one color blooms a week later than the others.
Personal Preference Vs. Crowd Pleasers
Joseph also had a tomato phase when he raised tomato plants in a “giant, jungle-ly mess” but he had to quit after developing contact dermatitis with tomato foliage. Plant breeders becoming allergic to their subject happens more often than you’d think.
He was listening to public radio’s “The Splendid Table” when the host at the time, Lynne Rossetto Kasper, lamented that no one had ever named a tomato after her. That gave Joseph an idea. He had crossed Matt’s Wild Cherry and Black Krim, his two favorite tomatoes. He offered Lynne a taste test of the F2 population of the cross. Whichever tomato she liked best, Joseph would stabilize and name after her.
The taste test was back in 2010, and he did in fact name a tomato for her. The one she picked had a wine-y, earthy flavor. Though Lynne Rossetto Kasper tomato seeds have never been commercially produced, they do circulate in seed exchanges.
Joseph and his friends also taste-tested the F2 population of the Matt’s Wild Cherry and Black Krim cross. Perhaps surprisingly, no two people picked the same variety as their favorite. In fact, one of Joseph’s friends hated the variety that Lynne had chosen.
“Tastes really can vary quite dramatically,” Joseph says, noting that it’s another reason why breeding your own fruit and vegetables is so fun. You can select offbeat flavors you love that are not for everybody.
Commercial growers will always aim for crowd-pleasers that are sweet and sour, with lots of sugar and lots of acid. As a home tomato breeder, you don’t need to worry about pleasing everyone. It’s your personal preference that matters — not the variety’s marketability.
Likewise, commercial breeders of table grapes always produce “sugar bombs” that are intensely sweet. Joseph says grapes have incredible, elaborate, complex flavors and can taste like a million different things, so foodies will enjoy home-bred grapes more than commercial grapes.
Tips on Selecting the Best Tomato Plants
In selecting the best tomato plants, Joseph considers how they perform over the whole season. If early-season fruit show promise, he still waits to see how those plants will person in summer heat and if they are prone to disease. Plants that falter later in the season are not winners.
Fruit from the same tomato plant will all be genetically the same. Still, there will be variations between the fruit that are based on when the flowers grew and what the weather and light conditions were as the fruit developed.
“There’s a fraction of a chance that there was a mutation on a single branch of the tomato plant, but that’s small enough to not be relevant,” Joseph says. “Generally, you want to look at the plant as a whole, not the individual tomatoes.”
Ask which plant has the biggest fruit, which plant is the healthiest, and which plant is producing the most tomatoes — not which individual tomato is the biggest.
On the rare chance that there was a mutation on a certain branch, you’ll notice a radical difference. For example, on a Black Krim plant you might notice one yellow fruit when the rest of the fruit are maroon. This is called a “sport.” If you save the seed from that sport, the next generation of plants will likely have yellow fruit too.
“If you saw something like that, definitely save some seeds and see what you get, but you could get a variety of things depending on how that mutation developed and where on the plant it developed,” Joseph says.
Variegated Plants and Mutations
“Plants can have mutations in different cell layers,” Joseph says. “The best example of this is variegated plants.”
A variegated hosta with a white leaf margin has two genetically different types of cells in the same plant. The cells that create the white leaf margins have no chlorophyll, which explains why they are white. The green cells are the regular kind of cells with chlorophyll.
“If you take seeds from a variegated hosta, the seeds will be produced either by the white cells or the green cells, but you won’t get both,” Joseph explains. “So if you have a white variegated host, usually if the outer part of the leaf is white, the seedlings will be a hundred percent green. And if the center of the leaf is white, then the seedlings will be a hundred percent white and die because they have no chlorophyll.”
How to Stay Organized While Breeding Plants
Keeping a record book of what crosses you made and when is really helpful, Joseph says. He also finds it useful to make code numbers, like BK-MC 20, for Black Krim and Matt’s Cherry, plant 20.
“Those numbers and codes sort of keep a little record of what crosses you’ve made,” Joseph says.
Joseph also keeps a Word document organized by year that records what day he made each cross and how many seeds he has of each. He can go back and find the parents and ancestors of each cross.
I hope you enjoyed my conversation with Joseph Tychonievich. If you haven’t listened yet, you can do so now by clicking the Play button on the green bar near the top of this post.
Have you created a new cross through plant breeding, whether intentionally or unintentionally? Let us know in the comments below.
Links & Resources
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“Plant Breeding for the Home Gardener” by Joseph Tychonievich
“Rock Gardening: Reimagining a Classic Style” by Joseph Tychonievich
“The Comic Book Guide to Growing Food: Step-by-Step Vegetable Gardening for Everyone” by Joseph Tychonievich and Liz Anna Kozik
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