Welcome to Plants People Science, a podcast of the American Society for Horticulture Science. We're glad you're joining us today. I'm Kurt Rome, University Professor at the University of Arkansas, and I'm joined by my co-host, Samson Humphrey. Samson, how are you today?
Sam HumphreyI'm doing fantastic. I am in the air conditioning where I have not been recently. I've mostly been in the greenhouse. It's like 89 degrees in there from my experiment. And I'm from Florida, so I actually really enjoy it, but my coworkers don't like it so much. Kurt, how are you?
Curt RomI'm doing real well. Samson, I know you're in the midst of doing your PhD research. Uh uh, how's it going?
Sam HumphreyOh my goodness. I have recently been able to use more interesting machines than usual, so that's been a lot of fun. Um the research itself is going a little bit slowly, but I find I find a lot to enjoy about it. And you've been doing a lot of gardening this summer, haven't you, Kurt?
Curt RomI I have been gardening. Gardening is, you know, my my major hobby. I love gardening. Uh my partner, my spouse, and I are gardeners and spending a lot of time there. And you know, uh, although I'm a daytime horticulturist and a scientist, that's that's my daytime job. Uh I I it carries over into the evening. And right now, at this time of year, I got so many things blooming in my garden. And that kind of brings me to today's topic. I'm just now past uh peak bloom on my roses, and they were glorious this year. We had a really good rose season. So today we're gonna talk about roses.
Sam HumphreyIt's very exciting, and I'm really looking forward to this too. I have roses for the first time, and they are really stunning. But these roses that we're gonna talk about today are just a step beyond. So today we are talking with David Slezak, and let's take a listen to this interview.
Dr.
Curt RomDr. Zlesak, it's wonderful to have you here today. Uh, before we get into today's conversation, let me ask you a question, Dr. Zlesak. Uh, do you prefer to be called Dr. Zlesak? Or for the conversation today, can we call you David? Yeah, please call me David. Well, that's wonderful. Call me Curt, and and of course, we have Sam on the other end of the line here, too. So I have heard the rumor that you're a Rosarian. What is a Rosarian?
David ZlesakOh, that that rumor is true. So it's just a crazy person that loves roses. I'm actually through the American Rose Society a master rosarian because I've been doing it uh for a long time and um been a consulting rosarian too. So with the American Rose Society, if if you're part of their educational um program, that means that you go out, give talks, and help with educational um articles and things for promoting roses. Um you can be a consulting rosarian. And I've done that for a while.
Sam HumphreyThat is so cool. Rosarian. I almost want to study roses now that I know that. That's amazing.
David ZlesakI hope you do. We need more. That'd be great.
Curt RomI do have a take that back. You're you're, you know, a person that likes roses isn't necessarily crazy. I just think that's really uh well cultivated.
David ZlesakThank you. I I love that. That's true. Maybe if you looked at my yard, you'd you'd change your mind. But um, okay.
Sam HumphreySo what what got you here? How did you become a Rosarian?
David ZlesakUm when I was a kid, um about eight years old or so, um, I loved gardening. I grew up in Milwaukee, and my grandparents lived on the other side of the state of Wisconsin. And I always loved going to visit with them. And and by that point, they sold the large farm and they had a little hobby farm. And it always helped me feel connected uh with grandma and grandpa uh when I'd go visit them and see their garden, take walks in nature, and then I'd go back to the big city with my parents and live in a house on a very small uh lot. So being able to grow some plants and pots inside and a little bit in the small garden space that we had uh brought a lot of joy to me. And I used to watch uh the PBS special called The Victory Garden with Bob Thompson and and um other hosts over the years, and I learned about different kinds of things that gardeners grew, vegetables, different types of flowers. And I tried to grow a little bit of each one of the key things that they were talking about. And one day they had a program on roses, so I knew that I needed in the spring with the money I saved up from Christmas and birthday money, uh, when we went to the garden center to get a rose bush, and that's where it started. Um, I had one rose bush for a number of years. My dad helped me protect it for winter there in Wisconsin. It gets pretty cold, and and and then later that that passion grew.
Sam HumphreySo, where'd you go from there, from this childhood to, I assume, college? Can you walk us through that?
David ZlesakYeah, even even before college started, when I was 13 years old, in the Milwaukee um Sunday newspaper, there was an article about uh Will Rattler's rose breeding hobby. And he was the director of Brenner Botanical Gardens. And they they were known for their roses. And he was breeding roses as a hobby at that point. It was before his famous rose knockout came on the market in 2000. This was back in 1984. And um, I was just inspired by being able to cross plants and work with diversity. I loved art, I loved science, and breeding plants
seemed really fun. And I enjoyed roses by then. I wrote to him, he wrote back to me, and um that's where it all started. He connected me with an older gentleman that lived in the same suburb as my family that became like a grandfather to me. I'd go visit him once a week and learn about rose breeding from Elton. And I'm I'm in touch uh with Will Rattler even uh these days. So he's a dear friend. I was even on the phone with him yesterday catching up about roses. So that inspired me to grow my love of horticulture, keep it growing with plant breeding as part of it, breeding roses, and then um enjoying other plants too, and then eventually having that um desire to go to college to study horticulture for my bachelor's degree.
Curt RomYou know, roses are a quintessential garden plant. Uh horticulturally, how long have we been cultivating roses as garden plants? And when did kind of rose breeding start to emerge as a science or a discipline?
David ZlesakThat's a really good question. So um controlled breeding is credited as starting with roses in about the mid to late 1800s. But but as he described, you know, roses have been loved by by people for many centuries, thousands of years, different cultures around the world. And some of those stories about some of those key roses, you know, we don't know all the details. There's some mystery. Um and what one thing that that really makes me smile and inspires me is uh, for instance, the Damasque roses that that are used for rose essential oil for perfumes and candies and other things. Um we we we learned with some modern tools, some genetic tools, that they're actually um three-way interspecific hybrids uh through the Silk Road, combining uh species from the east and the west, and even the north there in Syria, Damascus. Uh so Rosa Fechinkoana from further north, um Rosa Gallica from Europe, and um Rosa Mashada also from Asia, all in that that meeting place where East meets west, and somehow people are growing roses, maybe chance seedling started to give us those very fragrant roses that um are still the staple of the perfume industry today. There's there's key historic roses from parts of Asia, some of those roses that have bright yellow flowers, rosa fetita, and also um some of the variations of it, like Persian yellow and Austrian copper, some of today's genetic uh tools um helped reveal that that Austrian copper through different collection sites throughout Iran and the the region are basically have the same fingerprint. And these these historic roses are near sterile, some of them. And they they were propagated likely through through rhizomes and suckers. Uh so there's rich histories of people domesticating, enjoying the roses in their their region and then sharing them. Old Blush, that that key historic um rose from China that brought repeat bloom um into our modern roses, um, is an ancient Chinese art for over a thousand years. And in the 1700s came to Europe and is in the background, or at least that mutated gene that allows for continuous bloom in most all of the cultivated roses that we could find at our garden center today. So there's rich histories of um cultures and places. And then by the mid to late 1800s, especially in France, a lot of different nurseries started to do controlled rose breeding, maybe inspired partly by dog breeding and keeping pedigrees and and um forming breeding programs.
Curt RomWell, that's interesting. So they made that that those fragrant roses, uh at least in part, came across the Silk Road. So we're really talking about these kind of synthetic uh hybridizations that occurred in the first and second century BCE. So thousands of years uh that we've we've seen those combinations. And it's really cool that you uh you know that there's these techniques to go back and fingerprint and put together some of that chronology.
David ZlesakIt's amazing. Yeah, there's a lot of a lot of things to revisit, assumptions that that we have of origins of different plants, and yeah, it's really wonderful to be able to um hopefully answer some of those questions and have newer, hopefully more accurate perspectives.
Sam HumphreyYeah. So how through this whole long history, through many countries, several continents, uh how have consumer preferences changed? What do consumer preferences look like for roses?
David ZlesakYeah, that's a wonderful question. So so they've they've changed over time, even within a culture, especially with um, you know,
more recent times here is people use roses as a commodity, for instance, cut roses for Valentine's uh day here soon, and other holidays, of course, too, and celebrations like weddings and things. So different um cultures and places around the world have different things that they prioritize. And one thing that has really inspired me, the the Mayon family in France. Um, they've been breeding roses since the uh mid to late 1800s, one of the the early um families and nurseries for rose breeding. When when I've gone to go visit them, it's really fun to go through their research fields, and there's roses or selections that are just gorgeous there, but the time isn't right. They have partners in Japan and China, Indonesia, all over the world, and they they have um their their friends, their partners that represent their roses, and something might be you know in their field for a couple decades before the time is right, like the origami rose in in Japan, where the petals uh fold in a unique way. It's a beautiful rose. And um, so that's just one of many stories, and there's some secrets I can't tell yet, but someday, hopefully, the time will be right. Um broadly, people, you know, for cut roses, the goal is to try to bring fragrance into um cut roses. And of course, time is value, so the the longer uh a rose has a shelf life, you know, the more value it has, less thorns. So um, as you bundle them tight together, they don't rip each other and cause as many wounds for for a while. That that beautiful wide pedaled pinpoint center traditional kind of exhibition form for Rose Societies, Rose Shows was the standard uh from the 50s, 60s, 70s, 80s. And then David Austin roses, English roses brought that old-fashioned, heavily pedaled, um, maybe narrower pedaled, quartered, cupped, um, old-fashioned form uh back into popularity. Yeah, so so it's so it's really fun. There, there's room for lots of diversity.
Curt RomSo uh for breeders, rose breeders, you you kind of told us when that started. Has it uh been mostly in the academic science realm or has this been mostly hobby breeders? Um kind of tell us a little bit more about how have uh who's been the rose breeders and where have we seen those new the new cultivars emerge?
David ZlesakYeah, that's a great question. Um a little bit of everything, but what really drives the marketplace are the um independent nurseries, the commercial breeders. So for instance, uh the Cortez Nursery, which which is in Germany, uh northern part of Germany, uh they raise more seedlings than any other breeding program in the world. I I forgot the latest statistic, hundreds of thousands. Um I think it was maybe even over 400,000 new seedlings that Tomas Pearl germinates every year. So these these large companies, Mayand raises a lot, David Austin, Del Bard, um, a lot of European nurseries, um they're they're they're the leaders in terms of being able to raise the numbers with with roses being polyploid, suffering from some inbreeding depression over the years here, reshuffling the genetic deck of cards. We we have to raise more seedlings usually to find cultivar-worthy individuals. And there's a give and take in terms of we don't want to add too much genetic diversity because we fix these key traits that we love, like repeat bloom and and you know, stem length and habit and disease resistance or whatever, that we don't want to shuffle it too far, but um far enough to get the new combinations that we need. So, in addition to private companies, um there's some universities still there's less than there used to be. Uh so Felicitas Veda, up in Agriculture Canada, she came up with the whole series of the explorer series of roses, all named after North American explorers. And they've become a staple up in the northern part of the United States where it gets cold and up into Canada, showcasing that roses can be low-maintenance
landscape shrubs, which is great. So at least a governmental program, and there are a few other university programs, but usually these days, those programs are more to generate populations to study genetic traits or things that they could grant money for versus being able to raise tens of thousands of seedlings every year.
Curt RomSo, in those large breeding programs, are those being operated pretty much with kind of traditional breeding methods? And is the academic realm maybe using different technologies now and in and and giving us a little more of you know the fundamental knowledge and science, uh, the genes, and and can identify uh useful traits a little more. Tell me a little bit more about the technology that might be used in the various uh uh aspects of breeding right now for roses.
David ZlesakYeah, that's a great question. I I think there's a great opportunity to use a lot more technology, a lot more markers uh to help propel rose breeding forward. Uh one of the challenges is that uh there's a lot of different traits that you need to bring together in order to have something that's commercial. And so I think that's slowed it down a little bit. Uh, one of the areas that I especially love to work with and help make contributions towards is disease resistance, resistance to um rose black spot disease. And um just last week um I was looking over some recent data, and we finally have markers for a gene. Um so we'll hopefully publish it soon. We'll see how quickly we could write it up. But um I'm excited about that. Um there's not too many markers out there for some of the market limiting traits in roses at the moment. So I think that's limited what commercial breeders um can use, and then also their desire to adopt some of that technology. So at some point, maybe if there's um a number of SNP markers that could be multiplexed, and um, you know, companies could could send some advanced selections and have um um genotype for a number of things affordably, things could really move forward more quickly.
Curt RomWell, David, work on black spot because I I love roses, and and I also have worked in sustainability, and one of my least sustainable things that I grow are roses, because it down here in the humid south, uh, black spot is is a real challenge from from a that's my hobby, uh hobbyist gardener speaking. So you you need to get that fixed, you need to solve that problem.
David ZlesakOkay, we're we're working on it. Um so so there's uh 13 different uh races of black spot, and I keep them um subcultured here in in the lab. And I've been um challenging over the last several years here hundreds of different rose cultivars and seedlings that are parents of different things, wild species, and there's different patterns of resistance that have emerged that correspond to different genes. So at least in my mind, I'm I'm imagining combining different genes together. There's roses that should be resistant to all 13 races, and I I actually have some. They're not necessarily the prettiest yet that tick all the boxes, but I I won't give up, Kurt. I promise I won't.
Curt RomWell, uh layer those genes because I I'm sure in my garden I have all 13 races. Because it seems to be a problem. So get that get that layered up. That was uh thanks for letting us in on that kind of a secret. I that sounded pretty, pretty, pretty fun to be talking on and working on. But thanks for thanks for sharing that.
David ZlesakOne story that um that I think about in light of light of black spot resistance is that what we're basically doing with studying black spot resistance now and the genes behind resistance actually started about 30 years ago, especially, where some of the the commercial breeders and folks like uh Felicita Sveda, Dr. Sveda up there at Agriculture Canada, um, was working on was recognizing that people were less willing to preventatively spray fungicides on their roses to have healthy roses. So selection for disease resistance became a higher priority. Cortez, Will Rattler, others stopped spraying their seedling beds. And early on, there wasn't that much that's still looked, you know, relatively reasonably good. And uh, through their commitment to truly select for disease resistance
as a market limiting trader earlier on in the selection process, they eventually got roses that that were healthier. And and then what myself and others studied today are those roses. What what makes those roses special? So the last few decades, what resistance do they have? And so it's just wonderful to build upon that work, that painstaking work that those breeders started. And at first were so disappointed because there wasn't that much that survived.
Curt RomWhat about other environmental challenges that roses face? So you mentioned the breeding program in Canada. I would imagine they're looking at winter hardiness and relatively short growing seasons. Down here in the South, you know, I uh I'm going through my own selection process of what will tolerate the summer heat. And also I have a problem with with variable winter uh temperatures. You know, uh today it's 70 degrees, and a week ago it was minus nine. Um and those are challenges. So are some of these breeding programs also evaluating uh and developing roses for environmental tolerances and regional adaptability?
David ZlesakYeah, they they are, which is wonderful. Um so Texas AM is taking the lead with heat tolerance over the years and monitoring their seedling beds and commercial cultivars for those roses that continue to bloom through through the heat. Um, and also roses that have some saline tolerance using systems like hydroponics and controlling the EC and such and seeing which roses continue to grow well. Well, one thing that's uh been been really fun to think about, at least for me, is uh Dr. Griffith Buck. He was a pioneer rose breeder at Iowa State University from, I believe it was the 50s or 60s through to his retirement in the early 80s. And he he was there at Iowa State, hot summers, cold winters, and he couldn't afford uh fungicides or at least enough to prevent and really spray everything was how the story went. So he selected for disease resistance enough of his material. Um that's where um Phosphatis Feta, Will Rattler, others have continued to push disease resistance forward. But his roses that could take the heat of summer and the cold of winter, interestingly did really well in Texas too. So sometimes we could find roses that have wider adaptability than what we would imagine. Sometimes, at least I would think, well, a rose that's adapted in Texas, the Texas heat would hate Wisconsin, but sometimes we find roses with expanded degrees of adaptation, which is really fun. And as a parallel to that, um, when the All-America Rose Selection Program, a national rose trial program, started in 1938. Um it disbanded 2012 when it disbanded, uh, some colleagues and I started the American Rose Trials for Sustainability or Arts program. And um we we have um gardens across the country that partner with the program, and we test roses regionally and give regional awards. Um so we we try to help inform consumers, people out there that would be interested in what roses are most adapted to their region with these regional awards on our website, trustedroses.org.
Sam HumphreyThat is so cool.
David ZlesakCan can other people join, or is it just gardens? Oh, that's a great question. So we're we're using the Copen Climate System versus the USDA Cold Hardiness Zone Map, just because precipitation and temperature come together for how well a plant can um you know grow. So we our goal is to have two official trial sites, hopefully, in in every Copen climate um area. So we we encourage folks to volunteer at the botanical garden or our extension site. Um data is taken monthly throughout the growing season. We um routinely present posters at ASHS on the latest winners and do things in a scientific way with blocking and everything so so people can participate by um volunteering at their regional sites. Um maybe if they want to at their extension site, maybe plant a collection of their regional winners as a way to uh showcase to the public in their region what roses do well and would be recommended.
Sam HumphreySo, Dr. Zlesak, what does rose breeding look like nowadays? Like walk us through what what it looks like from your perspective, a day in the life.
David ZlesakOh, um yeah, that's a great question. So for at least a day in in my life and in the rose breeding that that I enjoy doing, um right now, here in early February, I have uh new seedlings that are germinating. So I'm I'm potting them up and they'll they'll germinate over a number of months now, so
they're kind of erratic for uh when they germinate. So so I gave them um a warm and then cold stratification and then keeping them in a cool place. Um so if they get too warm, they'll go into secondary dormancy. So week by week I see what's germinating, and because I don't have a lot of space to have big trays full of seeds, I have them in in little bags with uh peat moss, and then I carefully uh transplant them into little cells one by one, keeping track of their um their parents and creating codes for them. So at this this point, there's young little rose seedlings. Some have little flower buds already starting, some are in the process of germinating. Uh, so that's one activity right now. Um, another activity that's that's maybe more of the research part of it is I I cleaned out uh a greenhouse here on campus where I've been growing roses all summer and fall for the black spot work. So I wanted them to be free of black spot in the greenhouse, so then we could carefully pull these off of them and in a controlled way put a particular race of the fungus in the lab and a container onto them and look at their reaction. So they're all shuttled into the cooler now to open up more space. So I go check them and make sure that if they need a drink, there's hundreds of roses in there. And a lot of them I'm done with now. Um, they're copies of what I have at home already, so I'll try to find homes for them come spring. Um, and then in the process, I'm imagining different crosses for the future for next spring. I'm buying supplies. I love to use little film canisters to store pollen and freeze pollen. So um, as a Christmas gift to myself, I bought a thousand of them off of eBay. So uh planning for the future, enjoying the moment, waiting for spring to uncover the potted nursery plants outside and go through the beds and prune them. So there's always something to do, something to imagine. A lot of fun.
Curt RomHow do you you have a heavy teaching load? So uh at the University of Wisconsin River Falls, where you work, uh, how do you balance your teaching and this real passion you have for rose breeding?
David ZlesakUm, that's a great question. I I just try to fit it all in and and just love it. So so in the evenings here, I'm potting up little rose seedlings. I'm um at the end of a teaching day, going to the lab, setting up a PCR reaction, going out, getting supper, and coming back, checking on it, and then going home. And um yeah, I'm grateful that I live close to campus, just a few miles, so I could just make little trips here, there, everywhere, and and just make it happen. And so a lot of the the research colleagues at University of Minnesota or or others through that arts program that I email with or talk on the phone with are are dear friends. So that that helps balance out my social life. And um I've friends, of course, outside of horticulture, but not as many.
Curt RomYeah, well, that's the the life of a teaching uh faculty member. I understand that.
Sam HumphreyThat's awesome. Yeah, I'm looking at the list of courses you teach now, and it's extensive. Oh my goodness. You got woody landscape plants, plant propagation, introduction to biotechnology. You seem to do everything.
David ZlesakYeah, especially as people retire and we don't refill their positions. Um, yeah, we absorb classes, go every other year to fit them in. But I am so grateful for the mix that um I'm privileged to be able to teach. So especially components of woody plant ID and culture. I teach a nursery management class here this spring too, and plant tissue culture. So so it all kind of comes together for the plant breeding and development that I love to do. I um what what what's actually um more popular than any of the roses that that I bred are the nine bark. Actually, the the nine bark um help pay for the roses at home. I have two acres at home, just stuffed with oodles of roses and um so and
then done some hydrangea breeding, breeding of other things too, a little bit. But um so the the roses are my number one passion. Of course, I love other plants too, and teaching courses like tissue culture, biotechnology, um, plant ID, all that together. Um is a lot of fun.
Curt RomSo, David, you know, you kind of told us about how styles of roses have changed, and you've given us a little bit of the the uh uh history of rose breeding and how technology is being implemented in that. But you know, the retail horticulture industries have really changed in the last 20 or 30 years, you know, with big box stores and and regional and more uh uh franchised nurseries. How has the how has the business changed uh uh during your career for selling roses and and you know, where is the market for roses now? Is it is it at the big box? Is it at our local nurseries or their specialized nurseries? Tell us what's going on.
David ZlesakYeah, it's changed so much. Yeah, you're right. So um one of the key reasons why that All America Rose Selection Program, which was industry driven, disbanded in 2012 is that over half of the dozen or so member nurseries went out of business. And we used to have nurseries that focused on roses. That that was their sole crop. And they would have field production, sell bare root roses to local greenhouses that would pop them up, force them, finish them for Mother's Day, sell them mail order. And with a lot of them going out of business, um the nurseries that picked up roses today are those larger nurseries which are wonderful that manage brands. So as brands became front and center, um, proven winners, first edition, um, garden debut, boom and easy, all these different uh wonderful brands that have a whole suite of different kinds of plants that a gardener would enjoy, whole range of shrubs and herbaceous perennials, some of them annuals too. That um it's those large nurseries that knew that they need to have a rose component. So these branded programs, these nurseries that aren't necessarily as committed to roses as the previous nurseries, that was their whole life. That was their bread and butter, just roses. Um, so they they're learning to appreciate roses and um the production has changed a lot too. So uh a lot of roses never see the field these days. They they they're never in the field for being a bare root first and then being put in a pot. A lot of roses are cuttings, being rooted any state of the the nation and greenhouses, and then just upshifted in pots, versus in the past when they were in the fields of Arizona or California for a year or two before they were harvested. There's still some of that. Of course, there's still bare root roses, and um, I think it'll, you know, continue. Um, there's a lot of local garden centers that would like to um get bare root and force them for two months and sell them. So just like you said, yeah, most of the roses are being sold through box stores. Um, so the statistics, you know, tell us that, you know, Home Depot is the number one place where people get plants, and then Lowe's is number two. These box stores lead the way. But the independent garden centers, of course, are critical, and that's where passionate gardeners could get more plant diversity, more cultivar diversity. There's still a few specialty rose nurseries that sell what are called liners, little root of cuttings and maybe four or five-inch pots. And you could get some of the heirloom historic, less common roses, which is wonderful. High country roses, Burling Leong, and in California, um, a number of different nurseries where you could still get some of these critical roses that would be important for me, like for research or for historical purposes, uh a rose variety that uh maybe your grandparents once grew that you'd love to grow to help remember them.
Curt RomSo, David, you know, here at Plants, People, and Science, we like to talk about plants, obviously, and we we've kind of talked about uh the science, some of the science. And uh I want to ask you a people question. So every scientist is driven by some questions. I mean, there's a passion piece, but there's this question, this quest that's back there. What is your rose question? What is your rose quest? I know you've got all these other plants that you like to breed, and and I apologize for not talking about them. Don't let them know that we're we're ignoring them. But for roses, what is the burning question? What what drives David?
David ZlesakOh, yeah, well what drives me is roses that everybody can grow. And I'm up here in the north, so that's a perspective that I have up here, ones that are hardy and healthy enough that they can be that low-maintenance landscape
plant that people can be successful with. So that's what drives me, be it selection for more winter hardiness, selection for black spot resistance. Um when I was a kid and I um got connected with my day-to-day rose breeding mentor, Elton, Elton Strach, um, at that point, you know, I was just mesmerized by just the range of colors and beautiful um roses that we could get. I bought, you know, these latest hybrid teas and things that I thought, well, I'm young and I I have some energy. I'll spray them, I'll insulate them for winter, you know, they're gonna make it, they're gonna be fine. But even when I did that, I still lost some and some still got disease. And Elton, he he appreciated these wild species and his wild species hybrids. And so I'd look at a rose bush that was like 10 feet tall of his that just bloomed for a month in the spring, but it was glorious when it was in bloom. And I thought, wow, all that space could be used for like a dozen hybrid teas. And after I started losing my hybrid teas, even though I did my best to care for them, I still lose some. Um, I began to appreciate um though those hearty, healthy, wonderful roses and the great diversity within the whole genus that Elton appreciated, and the singles, the semi-doubles, unique fragrances, all that diversity. So what drives me is roses that anybody can grow and enjoy.
Curt RomYou know, you said that early on you were inspired uh by Radler and his development, and he's credited with the knockout rose series. You know, of things in my lifetime that I've seen have tremendous landscaping impact. The knockout series really changed uh roses from being a specimen plant to a landscape plant. Uh give us a little background on the knockout series and and kind of the direction you see, maybe that heading, and and has it changed rose uh use as much as I feel like it has?
David ZlesakI think it has, yeah. It revolutionized uh the rose market. So uh Will there in Milwaukee, being director of Brenner Botanical Gardens, he had three to four thousand um what are called modern roses, hybrids, florabundas, grandifloras. Um, I heard one person say chemically dependent divas that need a fungicide fix every seven to ten days in their fur coat to tuck them in for winter. Um but I mean we all we all appreciate the divas in our life, but we could only care for so many, right? Um so so for um about 30 years before knockout came on the market, Will at home purchased and grew the better than average roses that that he saw at the gardens and innermated them. And he brought Black Spot home with him to try to get diversity, and generation after generation began to increase quantitative resistance in his germplasm. And he didn't spray with fungicides to see what truly was healthy. And then knockout, besides that elevated disease resistance, it grows and flowers um beautifully. So it keeps the mounded habit and blooms and blooms and blooms. So that that really set knockout apart. And um, I don't want to divulge all his secrets, but um, he he had it under trial at multiple nurseries. And um some of those nurseries said, Oh, it's just a simple looking rose, nobody would want it. And they said, No. And and then the nursery that said yes, um, counted piles, star roses and plants, it it revolutionized them, especially during the downturn in the economy. It kept them alive, kept them from going out of business, which is great, and revolutionized what's possible for roses, um, for everybody to enjoy them, that season-long flowering, that nice rounded plant habit, that elevated health. And um, with the success of that first introduction, the series um built in really good marketing and people being successful. And what one thing that makes me smile, one of my uh very first students, the first semester I was here, uh Zach Stino, um he graduated and eventually went to go work for Will as his rose breeding assistant. And um the the new Orange Glow knockout, or relatively new a couple years ago, uh the pollination occurred by Zach. So that that was this is really fun just to see the connections of people over time. My mentor, my mentee, of course, we're all all friends
and learn from each other. Um and so all the other major rose breeders in the world have used Will's knockout in their breeding, Mayan, Cortez, um, all these other breeders to try to meet that bar of elevated health that that Will set. So yeah, Will just really uh set that bar. So they're in Milwaukee in his residential yard, imagining roses that were healthier, whereas the key US breeders, at least in California, where their climate's dry, um, you know, doing what they're doing, didn't necessarily see that opportunity, maybe not being in the climate where their customers were. So um, imagine, ask what if. And just because other people or the people with lots of resources aren't pursuing it, doesn't mean it's not worth pursuing. So, so for me, as a rose breeder, I I cross divergent roses. I love to bring in North American species roses just to see what's possible, especially for disease resistance and hardiness. And even though I don't raise the numbers, I won't have the number of introductions as anyone else. You know, I just feel like it's a win if anything comes out of my program, which is basically our early generation uh kind of breeding program to help answer scientific questions. And um, so I've learned to have my expectations um be realistic, so I'm not too disappointed.
Sam HumphreyI was going to ask you one final question. I almost feel like you've answered it. I was going to ask, since age 13, you've written letters and dreamed of rose breeding, and you've come such a long way. I'm sure it takes a lot of grit and a lot of challenge, uh overcoming challenges throughout your career to get to where you are now. I was going to ask, what wisdom have you gained? But it sounds like it's the dreaming. It sounds like it's dreaming of the rose that could be the things you could. Could you have anything to add to that?
David ZlesakYeah. Asking what if. And my master's advisor had this phrase. Um try to get rid of market limiting traits to expand the market. So what's the limitation right now? Emerald ash bores for for ash trees, diseases for roses, maybe tenderness during winter, at least in my climate for roses or heat in yours, Kurt. So um so think about what are the market limiting traits, and then what can we do to alleviate those limitations? Daydream, ask what if, uh find wonderful people that are great friends and colleagues to work on projects together with, because in today's world there's so much technology, so many resources. Um, it's hard to do everything ourselves. So find a good group of people to dream with, support each other, and um have enough um things in the fire that when something's not working right, you know, you're getting joy from another project while something is kind of on the back burner.
Curt RomWell, David, thank you so much for this conversation. Uh my take-home message is I'm not going to stop dreaming about roses. I think I can do better. I know that there's more things coming in down the pike. I need to go back and look at some of the other roses that have special meaning. But thank you very much for for sharing your story today and in and helping us understand roses better.
David ZlesakWhat a beautiful crop. Thank you so much, Kurt and Sam. Thanks for this opportunity to share with the ASHS and beyond audience.
Sam HumphreyThank you.
Yeah, you know, that's it's that's part of the fun about being a professional horticulturist is teaching it and also then experiencing it. And you know, I I was really struck. I had never ever known what a Rosarian was. And now I'm educated. Now I know what a Rosarian is. And we actually talked to a living, breathing Rosarian today.
Sam HumphreyWe did. I'm always so pleasantly surprised with the ASHS community. I love that it's, you know, I I love my little, you know, my little within my field community. I get to know all those people. But within ASHS, I get to see so far outside what I do and the papers that I'm typically read. Um, I never would have known that I had ever spoken to a Rosarian. And I probably would never have learned that much about roses. But ASHS really, really helps with that.
Curt RomAnd one of the things that struck me, and it strikes me every time we interview somebody for this podcast, is there's one common element that all of our guests have, and you and I share it too, and that is a passion for plants and a passion for what we do.
Sam HumphreyAbsolutely. Kurt, I'm so excited to see you at the upcoming conference. I there is so much to look forward to. Thank you for meeting with me today and having this conversation with David Zlesak.
Curt RomWell, thank you, Samson. It's always a pleasure. And to our listening audience, if this interview resonated with you, I recommend that you renew your membership or you consider joining the American Society for Horticulture Science. And then you can become part of the interest groups like the Floriculture Interest Group, the Ornamental Breeding and Germplasm Interest Group, or if you're a teaching faculty member, the Teaching Methods Interest Group. If you'd like more information on the American Society for Horticulture Science, or as we say, the ASHS, you can go to our website, ashs.org. Thank you for joining us. Samson, it was a delight. As always, see you later. The ASHS Podcast, Plants, People in Science, is made possible by member dues and volunteerism. Please go to ashs.org to learn more. If you're not already a member of the ASHS, we invite you to join. ASHS is a not-for-profit, and your donations are tax deductible.
Sam HumphreyThis episode was hosted by Samson Humphrey and Curt Rom. Special thanks to our audio engineer,
Andrew Sheldorf, our research specialists, Lena Wilson and Andrew Sheldorf, our ASHS support team, Sara Powell and Sally Murphy, and our musician, John Clark. Thanks for listening.