Science Friday - Everything You Never Knew About Squash And Pumpkins

Episode Date: November 26, 2025

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? In a conversation from 2023, 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.Guests: 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.Transcript is available at sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hello, it's Flora Lickman, and you're listening to Science Friday. Tis the season of squash. So today on the podcast, we are bringing you a conversation from the pantry. Ira is celebrating all things cucurbita and fielding your burning squash questions. Let's go. Now, you can see squash everywhere, right, in this holiday season. You've got those carved pumpkins. They're actually squash, believe it or not.

Those giant award-winning pumpkins. pumpkins or 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 squash, pumpkin, pumpkin program. Welcome to Science Friday. Hi, Ira. Thanks for having me on. How did you get interested in squash and pumpkin breeding? Yeah, I suppose it's kind of a different type of profession.

But yeah, you know, 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 it was the coolest thing in the world. And it's what got me started. Kind of motivated me to go on and study plant bringing genetics. I understand this year's world record for pumpkin was nearly 3,000 pounds.

That's right, 2,700. How did growers get pumpkins to grow so? big? Well, it's nature and nurture. So you need to have the right seeds or the right, you know, the seeds that have that genetic potential. And then you need to have the perfect growing conditions for those seeds for that plant. Can I, can I buy seeds and grow my own giant pumpkin? You could. So the variety that, you know, all giant pumpkins are thought to come from is called a Dills Atlantic Giant. So it was developed by a farmer in Canada in like the 1970s. So you can get that seed, but that's actually not your best bet.

Oh, no. 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. All right. Let's get into some basics here. Pumpkins and squash are part of the curcobit, the cucrobit family. Is that right?

What other plants are included in cucurbit? That's right. They're cucurbitis from the cucubatacee family is the full name there. call them cucurbit, so it includes, like you said, squash, pumpkins, melons, cucumbers, watermelons, wax cords, pretty much all of your binding fruits and vegetables that you know about are, well, they're all fruit. But they're cucurbits. Cucurbit, thank you for correcting me on that one. So what's the difference between a summer squash, let's say, versus a winter squash? So that's all about the time that you eat the fruit.

So a summer squash, you eat at before it's mature, whereas a winter squash, you eat at physiological maturity or when the fruit and the cedar completely developed. So it's, you know, eating it at 60 days versus eating it closer to six days after pollination. Six days? That's all it takes. Six to eight days after pollination is a summer squash or zucchini is usually, yeah. And then the winter squash you say take 60 days. That is a difference.

Yep. What is the, speaking of differences, what's the difference between a gourd and a squash? You know, 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. Now, I look this.

It's sort of how I define it. Yeah. I look this up in wiki. The Wikipedia says that gords have been found in sites dating back 30. thousand BCE. That's astounding. So, yeah, the 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.

Crystal in Rochester, New York. Hi, Crystal. Hi, there. Hi there. I was wondering, so I grow pumpkins myself and like 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 a pumpkin? Good, good question. Let me ask, is there not pumpkin in a can of pumpkin, Dr. Hernandez? So not what we would call a pump. So we typically would call a pumpkin like something looks like a jack-lantern, right?

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 Lantern, or more like a butternut type of squash. Wow. So in a lot of other countries, they call eating squash a pumpkin. Right.

Now, most of us have gone pumpkin picking it, but you've worked on breeding pumpkins, specifically for these you-pick-em-up operations, right? What are the traits that the you-pick farmers are looking for? 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.

It doesn't have a handle, right? 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 to having a handle with a really good attachment on that pumpkin. And then from there we look at, you know, 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.

Does the handle have a scientific name to it? The peduncle. Now, as you're growing and designing pumpkins, are there any other decorative pumpkins, are gourds? Are there trends going on? Yeah, I would see, you know, something that I'm seeing now is, like, 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-lantern. It's a cucurita maxima, and so I'm starting to look at those now as well.

You know, I think I hear about a story like this every year. Someone throws out a pumpkin in their backyard or into the... a compost heap, then you've got a pumpkin patch the next year of all these seeds have sprouted. How likely is this to happen? A seed all the time. We call those volunteers. Volunteers. Chris, have you tried that yourself with the pumpkin?

Throwing it back there? Growing them in the compost. Yeah. You know, not in the compost pile itself, but they do do well if you grow them on kind of a mound of compost. Yeah. That's kind of like you mound up the soil. That's a good forum. love growing like that.

I know that you're currently breeding acorn squash. What are the traits you try to optimize for? So with acorn squash, we, like I said, we kind of like those grower traits, which I think of like good disease resistance, you know, 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 for bricks. We actually freeze them and then we squeeze them to get that bricks concentration. Freeze them and squeeze them.

I have to remember that about squash. Let's go to Frankie in western Massachusetts. Hi, Frankie. Hi there. Hello. Hi there. How's it going? Fine.

Go ahead. So I was remembering when I was a kid, I read one of those little house in the prairie books called Farmer Boy. And in it, at one point, Almanzo decided to grow a pumpkin using milk. He kind of 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, like, 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. Chris, have you heard about this? 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 that calcium might help with the fruit development, at least from milk, we don't see that. Well, thank you, Frankie. That was an interesting question. Of course. Thanks for the insight. You're welcome.

Chris, what's the biggest challenge to designing new foods here, especially with your squash? Wow. Yeah, I mean, there are a lot of challenge. What's the biggest challenge? We know with squash and pumpkins, the hardest part is they take up so much space. So it's really hard to have, like, 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. Well, before you go to the break, I want to get to Kirk in Portland who has a really interesting question. Hi, Kirk. Welcome to Science Friday. 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 plowing plants like marigolds and zinias and dahlias. I've had success with that. You've got to get to your question because I're running out of time. 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. Wow. Okay.

Chris, what do you think of that? I would be surprised if a gourd was apparent 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 save seeds, you had that gourd genetics in there. Can any of them cross-pollinate and you get some weird answer at the end? Oh, yeah. So within a species, they can cross-pollinate. So zucchini and a jackliner

can cross-pollinate. pollinate a gourd, you 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 should really need to kind of keep the bees out and do the pollination yourself. That's the surest way to make sure you get with you. Keep the pollination yourself. A little paintbrush with the back and forth for the flowers? 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 the next in the morning we take the male off the plant and we remove its flowers and we use it like a paintbrush, the male flower on the female flower, and then we then we close the female flower back up to keep the bees out. Wow, that is fascinating. Dr. Hernandez, thank you for taking time to be with us today. Yeah, thank you. It was great being on.

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. Today's episode was produced by Shoshana Buxbaum. I'm Flora Lichtman. Thanks for listening.