carrots: their history, challenges, and how to grow them, with breeder dr. phil simon

HOW DO YOU BUILD a better carrot for organic farms and gardens, and how do you grow one for the best results? I discussed those topics with longtime carrot breeder Dr. Philipp Simon, who shared  their fascinating history, too—like who knew that the modern carrot’s ancestors originated in Afghanistan, and where the genetics for different colors of carrots came from?

Phil Simon has been breeding carrots for more than 40 years. He holds a joint position with the USDA’s Agricultural Research Service and the University of Wisconsin-Madison’s Horticulture Department. More likely than not, you’ve eaten carrots with genetics that have come from his breeding work, which today focuses on challenges including tiny pests called nematodes, and breeding varieties with more vigorous tops to stand up to weed pressure.

We talked about colorful carrots–orange wasn’t always the standard issue–and why a successful harvest of carrots starts with the same critical first step: cultivate, cultivate, cultivate that soil deeply.

Read along as you listen to the February 1, 2021 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).

carrot history, and how to grow them, with dr. phil simon

Margaret: Hi, Phil. I’m glad to finally speak to you. So you’re what’s called a public plant breeder. Can you tell us what that is, first off?

Phil: [Laughter.] Right. What that refers to is the differentiation between industry or seed-company breeders and those of us that are working at universities, and in my case, USDA and a university. So that’s what that refers to.

Margaret: Yes. And University of Wisconsin-Madison has quite the roster of esteemed public plant breeders, many of whom I’ve spoken to over the years. Quite the set of colleagues.

Phil: Yeah, it’s a great place to work. Since my program is a USDA program, which has a national U.S. focus, it’s important to be at a place where I can have colleagues to talk about business, as it were, on a regular basis. This setting gives me that opportunity.

Margaret: The other day, in getting ready to speak to you, I watched a University of Wisconsin video, maybe 10 years ago or something with you, where you said something like that more than three-quarters of the carrots in the U.S. have genetic background that comes from the Wisconsin breeding program, or something like that. Tell me a little bit about the breadth of the impact that these 40-plus years of work have had on the carrots that we eat.

Phil: Sure. Well, like almost anything in science, the success that I may have had is built on the shoulders of those that were working on carrots before me. My predecessor had a very large program on breeding carrots for the U.S. market. The focus of my program, as his was, is on fresh market carrots, which accounts for more than 80 percent of the U.S. market. What that means is carrots sold as raw carrots, as opposed to canned or frozen or otherwise processed. And there’s no other public program working with a focus on fresh market carrots.

So at least in part, the success of the program is the fact that seed companies have relatively few places to go to find new carrots being bred. Not to say that they don’t breed their own, and I don’t mean to take anything away from their efforts. And in recent decades, there’s been a big push for a very focused breeding in the industry sector of vegetable breeding for carrots. But the plant material, the seeds that my predecessor and I had released over time, are widely used because they have been bred, aiming for the market qualities that the fresh market industry in the U.S. looks for.

Margaret: O.K. So taxonomically what’s a carrot? Because I think it’s, Daucus carota, I don’t know, subspecies sativus

Phil: That’s correct.

Margaret: … or something like that. Or Carota sativa I see also. Oh my goodness, I get confused because it sounds a lot like Queen Anne’s lace. [Laughter.] What is it?

Phil: Yeah, right. It’s an interesting crop because in fact, Queen Anne’s lace is carrot. It’s not just some distant relative, it’s the same genus and species as carrot [Daucus carota], which means that we can intercross cultivated carrots with that wild carrot relative that’s very familiar along the roadsides over much of the U.S., and in many cases, by the millions [laughter] along the roadsides in the U.S. So that’s the genus and species of carrots.

The wild carrots that we see as Queen Anne’s lace in the U.S. are very common around the world in similar climates where there’s enough moisture to sustain the initial growth of the wild crop, in this case, and not-too-hot, not-too-cold conditions. But wild carrot’s a fairly heat-tolerant and cold-tolerant plant, and so it grows widely. In fact, I’ve collected wild carrot in places like Turkey, Uzbekistan, and Morocco and other parts of the world. So it’s a common wild crop.

Margaret: I said in the introduction I had read on your website that carrots, one place they probably originated was Afghanistan. And you just mentioned some other places where there’s wild carrot. And I guess we’ve been domesticating them since around 900 or 1000 AD or something like that. Could we just have the super-quick version of how that worked?

Phil: Sure.

Margaret: The stages. Yeah.

Chicago Art InstitutePhil: Yeah, so there’s not an extensive written history of carrot, but the first record of carrots clearly being grown regularly as a root crop, around 900 AD in Afghanistan or that larger area of Central Asia, but probably focused primarily in Afghanistan, Uzbekistan, Pakistan. Again, that’s just based on written history, which again is very scant on carrots. The first written history indicates that that root crop was yellow or purple, not orange.

The first cultivated carrots were then reported, especially moving westwardly, by people, through Iran and into Turkey, into the Arabias, and somewhat north into Greece, but probably more so a little bit south to North Africa, where carrot was grown as a root crop. And then it seems like the first cultivated root crop carrots came into Europe around 1300 from North Africa, and may have come more directly through Greece and through Eastern Europe as well. But it looks probably more like it came from North Africa, starting probably as a purple or orange carrot, based on the written history.

And then around 1400, the first record of orange carrots showing up in written history and in art show up in Southern Europe, in Spain and Germany. And then they moved north and became very popular in the north, because it’s a nice crop for growing in Northern Europe’s climates. And literally the rest is history. [Above, 1738 “Boy With Carrot” painting by Francois Boucher, Art Institute Chicago collection. Note that the carrot isn’t orange.]

Margaret: Yeah. So in the years you’ve been breeding, kind of there probably have been various goals along the way, landmarks genetically that you were seeking to improve. But now you’re heading a project focused on breeding for organic growing. So can you tell us why that’s important? I don’t mean politically, philosophically—what people believe about organic or not organic. I mean, practically speaking, it’s very important in carrots because…

Phil: Because practically speaking, it’s been estimated in 2019 that 16 percent of the U.S. carrot crop was growing under organic production management conditions. That’s a large percentage. There are a few crops with that percentage of the total crop nationally being grown with organic production techniques. So dollar-wise, it’s a critically important crop.

Some of the big growers are major suppliers of some of the chain stores that provide groceries. Target, for instance, would be one, Walmart, where organic produce has become quite popular. And then there are many, many small-scale growers that provide carrots typically much more locally, but on a regular basis. It’s a regular crop grown by very, very many of the small-scale Community Supported Agriculture [CSA] type growers, if your audience knows what that refers to, where you can get vegetables locally.

Margaret: Right. Even growers who aren’t farmers and who aren’t organic, in some areas, aren’t they losing access to some chemicals and spray controls, fumigants and spray controls that used to be… Well, that are almost essential for combating some of the opponents of carrots in the field? I mean, aren’t those being gotten rid of, certain chemicals?

Phil: Indeed they are. Indeed they are. Yes. Whereas the organic industry is mandated to not use these chemicals, even the conventional growers are losing access to them. And certainly, any conventional farmer would prefer to use less inputs if those inputs are fertilizers or water or pesticides. So it’s an economic issue for all carrot growers.

Margaret: That probably brings us to those tiny little creatures that I think there’s more of them on earth than anybody else [laughter], the nematodes. Doesn’t that bring us to them because that’s one… Is that a fumigant that is used to usually combat them? And a certain species of them has such a destructive impact on carrots, doesn’t it?

Phil: Yes. It takes some fairly potent chemicals to fumigate the ground before a carrot crop is grown if you’re going to control nematodes of than ground. And those chemicals have a heavy environmental burden in the sense that they release organic volatile chemicals that go into the atmosphere and are hard on the atmosphere. And not to forget that these are also… The people that apply these are very well-trained, but having said that, it’s a dangerous product to be handling. So it’s better for everybody if they can be used less. So we’ve been having a big focus on breeding carrots with nematode resistance for that reason.

Margaret: Right. So this is the Carrot Improvement for Organic Agriculture project that you are in charge of, and that you’ve received repeated grant funding for, I believe.

Phil: Yes.

Margaret: And that’s one of the focal points, is the nematode issue. Is also weed pressure another issue with carrots? Because for any home gardener, I would say that’s one of the things that… They don’t like weeds. [Laughter.]

Phil: Right, right. Well, carrots are generally poor competitors with the weeds that are their neighbors in a typical garden, be it your backyard garden or a few hundred acres in California or Washington or Wisconsin. They’re poor weed competitors because they tend to grow relatively slowly.

So one of the focal points of the organic breeding project has been looking for carrots that both grow faster early and produce a larger top to compete better with the weeds around them. So that’s been an interesting part of the project.

When you’re breeding carrots, you’re interested in diseases of the tops, but typically haven’t paid that much attention to the size of the tops. So it’s brought our focus to trying to develop a crop, actually, that… If you have a crop that’s established quicker, it grows quicker as a seedling, it’s going to be able to harvest quicker, too. So that has some great advantages down the road for all growers as well.

Margaret: When we say the size of the top, do we mean the width of the orange or yellow or purple—the meat, so to speak, of the carrot—or the greens? Do you know what I mean?

Phil: No, we’re talking about the leaves on top.

Margaret: The leaves on top.; the literal top.

Phil: Yes, yeah. Right.

Margaret: O.K. So the more foliage that-

Phil: Above the ground.

Margaret: ... it produces. Right, right, right.

Phil: Yeah.

Margaret: O.K. I see. It’s interesting, I never… And of course now that you say it, it makes total sense. Of course it can outcompete other things sprouting adjacent if it has more going on up there of its own. It makes more of a territory of its own. It stakes a bigger claim.

Phil: Yeah, yeah. The big growers say that they sometimes, if they don’t catch the weeds early enough with their mechanical operations and a walk through with their help earlier in the season, it can cost up to $6,000 an acre just to pay for weed control. That’s a pretty steep price to pay.

Margaret: Wow. So carrots, when one tries to grow them at home—and I’m going to ask you in a minute for some of your advice on how we can do better as we approach eventually this spring in our gardens—but what are some of the issues that the nematodes cause? Or I mean, for instance, what causes some carrots to have those hairy roots up and down the whole carrot, or crooked… Well, crooked roots, I suppose, can be a mechanical problem. But yeah, some of the things we see, what’s the cause and effect?

Phil: Yes. The nematode problem typically starts in the fibrous root system, but it typically will create some knobbiness, some bumps on the surface of the carrot. But probably more importantly… Well, I mean, it’s certainly not more important, but that the effect of the nematodes starts early in the season and just suppresses growth over all.

But when that carrot does grow and there have been nematodes around, they’re invariably going to be somewhat bumpy on the surface. That makes them relatively unmarketable. Luckily, there’s a lot of genetic variation that we can tap into to eliminate them.

But at any rate, so by going to some of the other root defects, I guess I would say that you’re talking about there are various bacteria and fungi that cause rots of carrots, that typically are not very extensive in the Midwest. There is an insect-vectored, primitive microbe—a phytoplasm—that causes this hairiness on roots in typically the Midwest and Eastern production areas.

So there are carrot diseases and pests of other types, besides nematodes. Actually, the second most important besides nematodes, and maybe globally the most important, is the leaf disease that leaves to dieback and suppresses growth overall, Alternaria leaf blight.

But anyway, so carrots do have a fair number of diseases that will attack them. But I would say compared to certain other… When I talk to other plant breeders, it’s not as bad as what some plant breeders need to deal with. But yeah, we pay quite a bit of attention to diseases of carrots. [More on organic breeding efforts in carrots to tackle these obstacles.]

Margaret: I ordered carrots and I have carrot seeds, and I’m ready to go if the weather cooperates in a couple months [laughter]. So what would you say is… You’ve grown a few carrots in your life. [Above, pelleted carrot seed.]

Phil: A few, yeah.

Margaret: I bet you’re pretty good at it. In the backyard setting.

Phil: Well, we try. [Laughter.] We try to get a crop and we aim for it, yes.

Margaret: And we should say that for you, you grow them… They’re biennials, so they don’t make seed, which is your goal is to get seed for the next generation, improve your breeding, select from that, etc., etc. So you have a two year process each time.

Phil: No, we handle it in a year. We can talk about that if you want. But we-

Margaret: You fake it, right. I know.

Phil: … do get seeds within a year of planting. When we plant a seed, we will have a seed from that plant within a year.

Margaret: Oh! O.K., you speed it up. But to grow carrots for carrots, for dinner, how do you recommend that we can do the best? Because a lot of people have trouble with the sowing too thickly, or again, weed pressure, things like that. But what’s your sort of quick 101 on “this is what’s important when growing carrots”?

Phil: Yeah, most important is how deep have you cultivated your soil. If you’ve got great friable soil, meaning soil you can break up easily, and you haven’t dug more than a few inches deep, that’s how long your carrots are going to be [laughter]. They will at least bend or fork when they hit that harder surface beneath the softer surface they’ve been growing in, if you haven’t cultivated deeply enough or if your soils just don’t allow that.

That mandates the… The carrot cultivars or varieties, the orange ones, are sold primarily on the basis of shape. There’s about 15 or 20 different shapes of carrots that carrot breeders over the centuries have come up with. Some of those shapes are quite short. The most extreme is what I call the ‘Paris Market’ or ‘Paris Forcing’ type. I mean, I call it that because that’s what historically it’s been called. But your listeners may know it by other names. But it’s a carrot that typically is spherical and may only be 2, 3, 4 inches long. It’s an early carrot, but also it’s one that’s great if your soil conditions are really poor.

So for starters, to get a good carrot crop, you need to cultivate as deep as you want your carrots to be growing, unless you have really friable soil, like very sandy soil. Then it might not be so necessary. But even then, sand does form a hardpan if it’s not been cultivated before you get in there and plant the crop.

Beyond that, you want to make sure there’s enough organic matter in the soil. It helps to allow the roots to grow better. Rocks and sticks and even bits of let’s say corn roots from the previous year can get in the way, and cause carrot roots to take the path that leads them to be something other than a nice straight carrot, or fork, or something like that. So the soil preparation is most important critically.

Many growers use raised beds. Most of your listeners know what that means. So that helps, too.

I guess starting with that, you’re pretty much ready to go on carrots. You plant them as early as you can. You don’t want to plant them too early in climates like the Northeast or Midwest, where it’s going to be cool, because if the temperatures are below something like 50 degrees Fahrenheit on a regular basis for a few days on a carrot that’s getting to be thumb size or so in your garden, the plant will, instead of continuing to form that nice storage root that consumers like, will put its effort into producing a seed crop when exposed to that extra cold. That creates a carrot that’s generally not able to be consumed, because it gets very woody once that flowering process starts.

Margaret: What about spacing? Do I sow them to stand, so to speak, as far apart as they should be eventually? Or do I thin them, sow thickly and thin them?

Phil: So that’s another consideration. Generally, you get the best performance if you have the luxury of being able to thin them, meaning that you have enough seed that you can sprinkle a little bit extra. I would typically recommend, depending on how large of a diameter you’re growing, for some of the bigger-diameter carrots, I would say maybe 30 plants—you want to aim for 30 plants per meter, per yard. Which isn’t very many, but they really can benefit from that space.

If you’re growing a thinner, more narrow-diameter carrot, you may be up to a hundred plants within a yard, within a meter. So you’ll probably want to plant somewhat thick and then… They benefit from not being in an exactly straight line, but they’re pretty good at working around each other.

Margaret: Right. And keep them moist until they germinate for sure, like any seed, but-

Phil: Yeah, and crusting on that soil is really hard on that somewhat weak carrot seedling coming through. So once they emerge, you do want to get out there with even a… If it’s in your backyard, with a hose, let’s say, and sprinkle them down so that there’s not a hard crust on that soil.

Margaret: Right, right. Is there a color you’re working on now, or anything we’re looking ahead to?

Phil: Yeah, we’re working on lots of colors. Because as I mentioned, the first carrots were purple and yellow, and orange is really the modern carrot of about the last 700 years. There are red carrots that were primarily developed in the East.

So we’re looking at developing carrots for organic and conventional production with all of these different colors. Each of the different colors have some different nutritional aspect to them. So they’re all good for you in one way or another, and that’s something we talk about. But more perhaps immediately interesting is the diversity of color is really quite striking among some of these different carrots.

We started with carrots that were growing elsewhere in the world. So a lot of the purple carrots, for instance, started from a Turkish type of carrot that’s widely grown. Red carrots from the East, they were typically grown as carrots for processing, for cooking. So that creates some challenges in developing a carrot for a fresh market that is going to be eaten raw, because there hasn’t been any emphasis on fresh market flavor for a carrot that’s been grown for cooking.

Margaret: Ah!

Phil: So that’s one of the challenges we have in moving these new colors—new from the modern–colors, into carrots for today’s growers. So we need to work harder and we are working harder on improving flavor, moving in that good flavor from the best orange carrots into these carrots of these, what I call, novel colors.

Margaret: Well, Dr. Phil Simon from USDA and University of Wisconsin-Madison, I’m glad to talk to you. And I want to learn more, so I’m going to keep reading. I’m going to give lots of links for people to learn more about your work and about carrots and their history and so forth with the transcript of the show. Thank you so much for making the time today.

Phil: You’re very welcome. I appreciate the opportunity. Thank you.

more on how to grow carrots

(Photos except carrot seed and painting from Organic Seed Alliance and Carrot Improvement for Organic Agriculture project.)

MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the February 1, 2021 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).

  1. Cynthia Donahey says:

    I have played around with making carrot oil using a crockpot on low. I mostly use the resulting product for cooking. I have restricted myself to orange carrots and obviously need to try other kinds. maybe even carrot greems.

  2. Linda Truax says:

    I have tried growing carrots with not much luck. My Aunt in NB Canada always had the magic and grew beautiful carrots. I am going to try again this year with raised beds. Great information, thanks.

  3. Sean says:

    I’ve been growing carrots in a whiskey barrel container for about 5 years. I do different color carrots for my daughter. I let her harvest 5 at a time and she likes to guess which color is going to come out. I like the fern like look from the leaves in the container.
    There’s a good video on YouTube on how to make a template for growing carrots in a container so you don’t have to thin them. I use the template year after year.

    1. Lauren? says:

      Hello! How interesting! I grow carrots in 12” tall raised beds. They’ve been straight, we prefer the flavor of orange varieties over the rainbows so far. I was taught as a kid at the NYBG to drop in a radish seed with the carrot seeds, every so often in a drill. This helps mark the carrots’ location, before they emerge, and perhaps prevents that crust from forming. Personally, I hate thinning so I sow more sparsely! Last year I followed a recipe for carrot greens…nope, twas yucky.

  4. Ann says:

    I like growing carrots because the deer can’t get to them. I want to grow more root vegetables this year for that same reason. You have to have loose soil to grow them and I found they enjoy growing along green onions, garlic, or chives which makes sense since they both have a long growing time.

  5. Mark says:

    I’m fortunate to be able to buy from some of the local growers trialing these varieties. In a mixed-color bag of roasting root vegetables I recently got some purple carrots that were WAY better than the ones I grew myself 10 years ago. Color wasn’t superficial and the flavor was decent. These are worthwhile projects and it’s great to see successes in real time.

  6. Pollyalida says:

    Interesting interview! Love pelleted carrot seed. I hate thinning carrots and I never do a thorough enough job, resulting in a lousy crop of dinky carrots.. With pelleted seeds I’m finally getting bigger carrots! Though mine still can’t compete w the great carrots that our regional Field Goods group provides, those are some chunky carrots!

  7. Sharon B. says:

    I’ve read that it can be useful to grow carrots amongst tomatoes plants, at least in warmer climates (I’m zone 7b in Roanoke, VA). Since I just bought carrots seeds for the first time in years, I’m now wondering whether this is a good idea. Anyone have any thoughts?

  8. Irmhild says:

    Hello Margaret,
    well you are such an inspiration! I’m listening to all the podcasts and just getting so much information in each one. Incredible people who share so much. and lifting my spirits in this crazy time we are in. Plants make me feel so much happier.
    thank you.

    1. Carla D'Anna says:

      I’ve read the adult fly can’t get very high up, 60cm was quoted as their limit. Construct your raised bed to be taller than that or build an insect barrier around it to that height. Another tip was to make narrow width raised beds speculating it would be more difficult for the adult fly to land in them.

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