It’s a wonderful time of the year: squash, pumpkin, and gourd season. But how do those giant, award-winning pumpkins grow so big? And what’s the difference between a gourd and a squash?
Ira talks with Dr. Chris Hernandez, director of the University of New Hampshire’s squash, pumpkin, and melon breeding program to explore all things winter squash and answer listener questions.
- Learn more about UNH’s Cucurbit breeding program on their website.
A Visit To A Giant Pumpkin
Pumpkins can get pretty huge. Check out SciFri’s video about a 1,000 pound pumpkin!
Dr. Chris Hernandez is an assistant professor of Plant Breeding at the University of New Hampshire in Durham, New Hampshire.
Dan Souza is co-Editor of Cook’s Science: How to Unlock Flavor in 50 of our Favorite Ingredients (Cook’s Illustrated, 2016). He’s based in Boston, Massachusetts.
IRA FLATOW: This is Science Friday. I’m Ira Flatow, hanging out with Sophie Bushwick, Technology Editor at Scientific American. And for the rest of the hour, we’re talking food chemistry– the chemistry of cooking and the research behind developing new crops, specifically this time, squash.
Now, you can see squash everywhere in this holiday season. You’ve got those carved pumpkins. They’re actually squash, believe it or not. Those giant award-winning pumpkins are squash, too. How do they get so big? And what’s the difference between a gourd and a squash? And how do you breed a better squash?
We actually have somebody who knows the answer to all of those things. Dr. Chris Hernandez, Assistant Professor of Plant Breeding at the University of New Hampshire in Durham, New Hampshire. He’s director of the University’s Squash, Pumpkin, and Melon Breeding program. Welcome to Science Friday.
CHRIS HERNANDEZ: Hi, Ira. Thanks for having me on.
IRA FLATOW: How did you get interested in squash and pumpkin breeding?
CHRIS HERNANDEZ: Yeah, I suppose it’s kind of a different type of profession. But yeah, my dad was really into gardening. He got me into gardening. And I was doing some gardening at a community garden, and there was a guy there growing giant pumpkins. And I just thought that was the coolest thing in the world. And it’s what got me started, kind of motivated me to go on and study plant breeding and genetics. So–
IRA FLATOW: Now, I understand–
CHRIS HERNANDEZ: –it started in the garden.
IRA FLATOW: I understand this year’s World record for pumpkin was nearly 3,000 pounds.
CHRIS HERNANDEZ: That’s right. 2,700.
IRA FLATOW: How did growers get pumpkins to grow so big?
CHRIS HERNANDEZ: Well, it’s nature and nurture. So you need to have the right seeds or the right– the seeds that have that genetic potential. And then you need to have the perfect growing conditions for those seeds for that plant.
IRA FLATOW: Can I buy seeds and grow my own giant pumpkin?
CHRIS HERNANDEZ: You could. So the variety that all giant pumpkins are thought to come from is called Dill’s Atlantic Giant. So it was developed by a farmer in Canada in the 1970s. So you can get that seed, but that’s actually not your best bet. So–
IRA FLATOW: Oh, no.
CHRIS HERNANDEZ: –kind of your over-the-counter seed is not really what growers are using now. They kind of have their own exchange of seeds where there’s been selecting and breeding as a community. And so those seeds are kind of what you want to get.
IRA FLATOW: Yeah. We actually have a video of a giant pumpkin grower who entered into a contest. SciFri’s Flora Lichtman videoed this, and you can see this video– it’s amazing– at sciencefriday.com/pumpkin.
All right. Let’s get into some basics here. Pumpkins and squash are part of the cucurbit– the cucurbit family. Is that right? What other plants are included in cucurbits?
CHRIS HERNANDEZ: That’s right. There are cucurbits from the– Cucurbitaceae family is the full name there, but we call them cucurbits. So it includes, like you said, squash, pumpkins, melons, cucumbers, watermelons, wax gourds– pretty much all of your vining fruits and vegetables that you know about or– well, they’re all fruit, but they’re cucurbits.
IRA FLATOW: Cucurbits. Thank you for correcting me on that one. So what’s the difference between a summer squash, let’s say, versus a winter squash?
CHRIS HERNANDEZ: So that’s all about the time that you eat the fruit. So a summer squash, you eat before it’s mature. Whereas, a winter squash you eat at physiological maturity, or when the fruit and the seed are completely developed. So it’s eating it at 60 days versus eating it closer to six days after pollination.
IRA FLATOW: Six days? That’s all it takes days?
CHRIS HERNANDEZ: Six to eight days after pollination is a summer squash or zucchini is usually– yeah.
IRA FLATOW: And then the winter squash, you say, takes 60 days. That is a difference.
CHRIS HERNANDEZ: Yeah.
IRA FLATOW: What is the– speaking of differences, what’s the difference between a gourd and a squash?
CHRIS HERNANDEZ: That’s actually kind of a contentious– it’s a bit of a debate among cucurbit scholars, I would say. If you look at the last five decades, there’s a lot of argument about that terminology. So I might get myself into trouble here. But I would say a squash is something that we eat. Whereas, a gourd is a hard-shelled, ornamental type of squash.
IRA FLATOW: Hmm. Now, I’ve looked at–
CHRIS HERNANDEZ: That’s sort of how I define it.
IRA FLATOW: Yeah. I looked this up in Wiki, and the Wikipedia says that gourds have been found in sites dating back 13,000 BCE. That’s astounding.
CHRIS HERNANDEZ: So yeah. Gourds are kind of more of like that undomesticated type. So I think my understanding is as far back as around 10,000 years ago, we were domesticating them.
IRA FLATOW: Hmm. All right. Let’s see if we can go to the phones and get a call in. Our number– 844-724-8255. Crystal in Rochester, New York. Hi, Crystal.
IRA FLATOW: Hi, there.
CRYSTAL: I was wondering– so I grow pumpkins myself and use them to make pumpkin pie and stuff. But one of my friends told me that if you get canned pumpkin it’s actually Hubbard squash, and that that’s better to use for making stuff, and I wondered if that was true. And if so, why do they use Hubbard squash? And why do they call it pumpkin?
IRA FLATOW: Good question. Let me ask. Is there not pumpkin in a can of pumpkin, Dr. Hernandez?
CHRIS HERNANDEZ: So not– not what we would call a pump– so we typically would call a pumpkin like something looks like a jack o’lantern. And that’s actually not what you want to eat. You can eat it, but it’s the lowest quality, I would say.
So yeah. That’s exactly correct. So a canned pumpkin is actually either a Hubbard, which is a different species from the jack o’lantern, or more like a butternut type of squash. In a lot of other countries, they call eating squash a pumpkin.
IRA FLATOW: Now, most of us have gone pumpkin picking, but you’ve worked on breeding pumpkins specifically for these “you pick ’em up” operations, right? What are the traits that u-pick farmers are looking for?
CHRIS HERNANDEZ: Yeah. So if you ask anyone in the pumpkin business, they’ll tell you that they’re not in the business of selling fruit. They’re in the business of selling a handle. So the handle is actually a trait that we focus a lot on.
Because if you think about it, you’re not going to buy a pumpkin that doesn’t have a handle. And you also couldn’t pick it. If the handle comes off when you pick it up, that’s not a good pumpkin. So we put a lot of effort and having a handle with a really good attachment on that pumpkin.
And then from there, we look at different types of colors, sizes. And then, of course, having a pumpkin that’s going to grow well for the grower. So it has that disease resistance and the yield potential. But yeah. The handle gets a lot of care.
IRA FLATOW: Does the handle have a scientific name to it?
CHRIS HERNANDEZ: The peduncle.
SOPHIE BUSHWICK: [LAUGHS]
IRA FLATOW: So yeah. [LAUGHS]
SOPHIE BUSHWICK: The peduncle. That’s a great name.
IRA FLATOW: Is that true for– then all veggies or fruits that have a handle would be called a peduncle?
CHRIS HERNANDEZ: Oh. Hmm. I’m not 100% sure on the answer to that one. But I know in squash it’s a peduncle.
IRA FLATOW: There you go.
SOPHIE BUSHWICK: In squash, is it called a pedunculated while it’s still on the vine? Or does it only become a peduncle after you cut it off?
CHRIS HERNANDEZ: So that– so I guess I would still call it a peduncle on the vine. So the pedicel is that part that holds the undeveloped fruit, and that matures into the peduncle.
IRA FLATOW: Now, as you’re growing and designing pumpkins, are there any other decorative pumpkins or gourds– are there trends going on?
CHRIS HERNANDEZ: Yeah. I would see– something that I’m seeing now is a lot of people are liking those white pumpkins. So we’re starting to do some work with developing pumpkins that have that white color that stay white. And also, I’m seeing a lot more round or stacker-type pumpkins, which is a different species than the jack o’lantern. It’s a Cucurbita maxima. And so I’m starting to look at those now as well.
IRA FLATOW: Let’s go to Bill in Eastern Maryland. Hi, Bill. Bill, go ahead.
BILL: Yeah. I’m interested– I love delicata squash. But they seem so– I seldom see them in the markets, and I don’t understand why. They taste delicious. Can you explain that?
IRA FLATOW: Do we have an answer there?
CHRIS HERNANDEZ: Yeah. That is a good question. So a delicata squash, pretty related to an acorn, usually a higher sugar content. Yeah, I guess– I don’t know. I know some people just think they’re too sweet. I’ve heard that as a complaint. But yeah, I can’t say, why on the market you don’t see that many delicatas.
IRA FLATOW: Yeah. Yeah. All right. Well, that’s a great question. I think I hear about a story like this every year. Someone throws out a pumpkin in their backyard or into their compost heap, and then you’ve got a pumpkin patch the next year of all these seeds have sprouted. How likely is this to happen?
CHRIS HERNANDEZ: I see it all the time. We call those volunteers.
IRA FLATOW: Volunteers.
CHRIS HERNANDEZ: Yeah. Volunteer [AUDIO OUT]
IRA FLATOW: Oh, we think we’ve– I think we’ve lost him there. Do you ever– did you ever do that, Sophie? Throw a pumpkin into your pumpkin?
SOPHIE BUSHWICK: No. No. I did worry that– apparently watermelons belong to the same group. And I did worry that I would grow a watermelon inside by swallowing watermelon seeds. But I never tried throwing it out in the yard to see what would grow. That’s awesome.
IRA FLATOW: Chris, have you tried that yourself with the pumpkin– throwing it back there.
CHRIS HERNANDEZ: Growing them in the compost?
IRA FLATOW: Yeah.
CHRIS HERNANDEZ: That is often not in the compost pile itself, but they will– they do do well if you grow them in kind of a mound of compost. That’s kind of like if you mound up the soil, that’s good for them. They love growing like that.
IRA FLATOW: I know that you’re currently breeding acorn squash. What are the traits you try to optimize for?
CHRIS HERNANDEZ: So with acorn squash we– like I said, we kind of like those grower traits, which I think of like good disease resistance, earlier– so they get a harvest earlier. And on the quality end, we look at the dry matter, which is kind of a proxy for starch. And then also the sugar content, or brix– we actually– we freeze them, and then we squeeze them to get that brix concentration.
IRA FLATOW: Freeze them and squeeze them. We’ll have to remember that about squash.
I want to bring in another guest to the squash convo to talk about the cooking side of things. Dr. Dan Souza, chef at America’s Test Kitchen based in Boston, Massachusetts. Welcome back, Dan.
DAN SOUZA: Thanks for having me. It’s good to be back.
IRA FLATOW: Do you have a favorite squash that you use or prefer?
DAN SOUZA: Yeah. I have a couple. So one of my recent faves is the honeynut squash, which I think our other guest can probably speak to how that came to be. But what I really like about it, it has a lot of the traits of butternut in terms of that really nice sweetness, but it is a little on the drier side. It browns really, really nicely when you’re roasting it. And the skins are a little bit thinner, so it’s one that I tend to leave the skins on. So I think that’s one of my faves.
And delicata doesn’t sound like it’s as popular as I think it should be. But that one also is– we call it kind of the easiest squash in the Test Kitchen because it does have super thin skins. There’s no peeling to it. You just slice it up and go. And I actually find it to be less sweet than other ones, which I’m curious to find out if that’s just my own perception of it.
IRA FLATOW: Chris, what do you think?
CHRIS HERNANDEZ: Huh. Yeah, I don’t know. We usually– so we normally measure the brix, which is not necessarily like the same as eating it sweetness. So we see that they usually have pretty high brix. But yeah, it could also just be that some of the varieties in the market just aren’t fully ripe that you’ve had, or that they just aren’t sweet varieties.
IRA FLATOW: Interesting.
DAN SOUZA: That’s interesting.
IRA FLATOW: Let’s go to Frankie in Western Massachusetts. Hi, Frankie. Hi there.
IRA FLATOW: Hi there.
FRANKIE: How’s it going.
IRA FLATOW: Fine. Go ahead.
FRANKIE: So I was remembering– when I was a kid I read one of those Little House on the Prairie Books called Farmer Boy. And in it at one point Almanzo decides to grow a pumpkin using milk. He digs a hole in the ground, and he puts a bowl of milk there. He puts a string in the bowl, cuts a small hole in the vine of the pumpkin, and puts the other end of the string in the vine, and the pumpkin grows huge. It becomes massive, and it’s all supposedly because it’s a milk-fed pumpkin.
And I’ve done some kind of cursory googling, and I cannot figure out if this is actually something that would work, or if this was some kind of invention of the author. And so I was wondering, is that something– is that a type of pumpkin steroid that people actually use or that actually works?
IRA FLATOW: Chris, have you heard about this?
CHRIS HERNANDEZ: I have, and I was actually wondering if milk and pumpkins would come up. A lot of giant pumpkin growers have tried using milk, and it doesn’t seem to help at all. So the idea is the calcium might help with the fruit development. At least for milk, we don’t see that.
IRA FLATOW: Well, thank you, Frankie. That was an interesting question.
FRANKIE: Of course. Thanks for the insight.
IRA FLATOW: You’re welcome. Let’s– so many people have questions. Let’s go to Donna in Florida. Hi, Donna. Welcome to Science Friday.
DONNA: Hello. I am– are you talking to Donna? It kind of cut out.
IRA FLATOW: Yes, I’m talking to Donna.
DONNA: OK, great. I have a question. I’ve kind of missed out in life because I don’t like watermelon or honeydew or cantaloupe or any of those. I don’t even like the smell of it. And I was wondering if that’s like– I can eat pumpkin. I can eat butternut squash, acorn squash. Is there some chemical that you know that’s in those particular ones, that like a subfamily or whatever, you know?
IRA FLATOW: Chris, you ever heard of that?
CHRIS HERNANDEZ: I mean, there are definitely some volatiles going on in there. I can’t name the exact chemicals off the top of my head here. But I do know that a lot of people, including my technician in the program, does not– they do not like the smell of the melon. It really bothers them.
IRA FLATOW: Ah. So it’s not uncommon. That’s interesting. Let me just give a break. This is Science Friday from WNYC Studios. We’re talking about squash, pumpkins, food science for the rest of the hour if you want to join us– 844-724-8255. Chris, what’s the biggest challenge to designing new foods here, especially with your squash?
CHRIS HERNANDEZ: Wow. Yeah. I mean, there are a lot of challenge. What’s the biggest challenge? Hmm.
IRA FLATOW: Yeah. What’s hard? I mean, do you do it the old fashioned way with pollination instead of with genetics– at least genetic engineering?
CHRIS HERNANDEZ: Yeah. We don’t do any genetic engineering, so it’s all kind of through traditional cross-breeding and that sort of thing. With squash and pumpkins, the hardest part is they take up so much space. So it’s really hard to have large populations that you can look through to find what you’re looking for because they just take up so much space. So that’s a challenge that I have.
It’s also always hard to know because when you’re breeding, it takes six to eight years to get that new variety. It’s hard to know what’s going to be popular six to eight years out– so that kind of prediction part of it.
IRA FLATOW: Well, before we go to the break, I want to get to Kirk in Portland who has a really interesting question. Hi, Kirk. Welcome to Science Friday.
KIRK: Oh, my gosh. Thank you for taking my call. Hey, I’m a retired science teacher from high school. And I’ve been having a garden for years and years. And I thought, you know, I’ll do what Gregor Mendel did, and I’ll collect seeds and cheaper way of growing flowering plants, like marigolds and zinnias and dahlias. And I’ve had success with that.
IRA FLATOW: You’ve got to get to your question because we’re running out of time.
KIRK: Yeah, yeah. I saved zucchini and spaghetti squash seeds, and I got gourds. So it seems like gourds must be some wild type of squash. Inedible, but beautiful.
IRA FLATOW: OK. Let me– Chris, what do you think of that?
CHRIS HERNANDEZ: Hmm. I would be surprised if a gourd was a parent in there. I’m wondering if maybe you had an outcrossing event where somebody was growing gourds near you. The bees moved it over. And then when you saved seeds, you had that gourd genetics in there.
IRA FLATOW: Can any of them cross-pollinate and you get some weird answer at the end?
CHRIS HERNANDEZ: Oh, yeah. So within a species, they can cross-pollinate. So a zucchini and a jack o’lantern can cross-pollinate. A gourd can cross-pollinate with them. Even across species, to some extent, they can do that. So if you really want to save your seed, you really need to keep the bees out and do the pollination yourself. That’s the surest way to make sure you get what your hoping for.
IRA FLATOW: Do the pollination yourself– a little paintbrush with the back and forth for the flowers.
CHRIS HERNANDEZ: Yeah. We actually– so we close the flower with a twist tie before they open. The day before they open you can tell because they start to get a little yellow at the tips.
And then we– the next– in the morning, we take the male off the plant. We remove its flowers, and we use it like a paintbrush– the male flower on the female flower. And then we close the female flower back up to keep the bees out.
IRA FLATOW: Wow, that is fascinating. Dr. Hernandez, thank you for taking time to be with us today.
CHRIS HERNANDEZ: Yeah. Thank you. It was great being on.
IRA FLATOW: Dr. Chris Hernandez, Assistant Professor of Plant Breeding at the University of New Hampshire in Durham, and he’s the director of the University Squash, Pumpkin, and Melon Breeding program.