Perennial rice: Plant once, harvest again and again : Short Wave Rice is arguably the world's most important staple crop. About half of the global population depends on it for sustenance. But, like other staples such as wheat and corn, rice is cultivated annually. That means replanting the fields year after year, at huge cost to both the farmers and the land. For years, scientists have been tinkering with rice strains to create a perennial variety – one that would regrow after harvest without the need to be resown. Today, Scientist in Residence Regina G. Barber takes a look at one promising perennial rice effort. It's one of a series of interviews we conducted live at the 2023 Annual Meeting of the American Association for the Advancement of Science (AAAS).

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Perennial rice: Plant once, harvest again and again

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EMILY KWONG, BYLINE: You're listening to SHORT WAVE from NPR.


Hey, SHORT WAVErs. So earlier this month, some of our team went to a big science conference in D.C., the American Association for the Advancement of Science, or AAAS. This conference attracts scientists from all over the world. I listened to one talk on invisible matter in the universe and another one from a Jordanian princess on strengthening science within her country's borders. Basically, it's a big party for science nerds. We had a blast. And we tried something new, live interviews with scientists on stage. We're going to share a bunch of those conversations with you in the coming weeks. To get us started, we have a pair of scientists who are tinkering with what arguably is the world's most important staple crop.

TIM CREWS: All of the cereals that we eat and most of the grains are annuals. You have to resow them every single year and harvest them. None of them are perennials, meaning they regrow after you harvest them again and again and again. Not just rice.

BARBER: Rice. That's what Tim Crews is focused on. He's the chief scientist and director of the International Program within The Land Institute in Kansas. Specifically, he's talking about a new perennial variety of rice that wouldn't have to be planted every year. And for the first time in probably 10,000 years of human rice cultivation, he says, the new strain stays productive crop after crop.

CREWS: And now it's gotten on to where it's eight consecutive harvests, approximately equal to the annual grain growing alongside as a check.

BARBER: I talked to him and his colleague Erik Sacks, a professor at the University of Illinois Urbana-Champaign. Erik studies rice genetics, the science behind this perennial rice and the impact it's having on the farming communities where it's being put to the test - in China.

ERIK SACKS: Humanity depends on basically three staple grains for survival. And those are rice, wheat and corn. And of those three, rice feeds the most people in the world today. About half the population depends on rice for sustenance. So it's hugely important.

BARBER: Today on the show, the science behind the rice that regrows on its own, an idea two decades in the making. I'm Regina Barber, and you're listening to SHORT WAVE, the daily science podcast on the road from NPR.


BARBER: I interviewed Tim Crews and Erik Sacks about this perennial rice on the Sci-Mic stage at the back of a busy expo hall.

So, Tim, can you tell us, like, how rice right now is farmed?

CREWS: Right. When we grow annual crops, you have to kill all of the vegetation every year and put your seed in the ground so that you don't have competition with other vegetation since we have to start from a seed every year. That's all well and good, except the ground is left bare for many months frequently. And what happens? Well, nutrients leach out. Dead zones in the Gulf of Mexico and 400 other river mouths around the world. You have soil erosion. You have loss of soil organic matter. You have greenhouse gases, all sorts of negative consequences of starting from scratch. And so, my gosh, if you have a crop that functions more like the natural ecosystem that preceded it, you're not leaching nutrients. You're not eroding soils. You're - this perennial rice actually shows that the soil was more fertile at the end of the 4 or 5 years than it was at the beginning. That's an agriculture that we can get behind.

BARBER: Erik, can you talk about anything else? What are the other benefits with labor costs?

SACKS: Right. So planting of rice is very labor intensive. So we have to usually start a seed bed. Then we transplant the rice into a field that's been plowed. That plowing takes effort, and all of that takes a lot of time and money. In a lot of the world that's still done by hand and it often falls to women and children to do that planting and transplanting. So if you have to do that every season, that's a big cost. It's a big labor expense. But if you can plant once and then harvest consecutively and get the same kind of yields over four years and you don't have to do that labor in your two, year three, year four, you save a lot of time. And you give the farmer, especially a smallholder farmer, a lot of extra time to participate in other important labor activities that could generate income. So this could be a great way to pull people out of poverty.

BARBER: And, Tim, what's happening right now with your perennial rice?

CREWS: Well, I'm going to let Erik speak to the breeding objectives, but there's a lot of work - now that there is a perennial rice, there's a lot of questions being asked about it. How does the soil microbiome change when you go from an annual to a perennial? What are the trace gas - greenhouse gas emissions like when you go from an annual to a perennial rice, given the concern of certainly methane? And how stable is the accumulated soil organic matter that you get when a crop is left in the ground for four years? And you don't have the tillage. Things that cause soil, organic matter and carbon to leave have been reversed. And so there's really exciting questions.

BARBER: So can you give us kind of the science of, like, how is this rice different from what - you know, what we have now?

SACKS: Yeah, sure. So the way this rice was developed, we crossed a domesticated Asian rice - so just a typical rice variety, actually a cultivar from Thailand - with a wild relative from Africa that's really good to regrowing. And it actually produces long, horizontal, underground stems, which, of course, we don't want, but we like the regrowth part. And then over many years, selecting for good agronomics, good yield and ability to regrow after it's cut back, selected a number of different varieties. So three of these cultivars have been released in China, the first one in 2018. And then they've been now available to farmers who have been rapidly adopting them and trying them out. And so that's where we - that's where it's gone on. And it's that breeding has all happened in Yunnan.

BARBER: The breeding, you said.

SACKS: The breeding has all...

BARBER: So how does the breeding actually work?

SACKS: Oh, OK. So that initial cross was actually a difficult one to make. You don't - if you cross those two species together, you often don't get any viable progeny back.

BARBER: How do you cross those two species together? What's the mechanics?

SACKS: You take the pollen on - of one of them...


SACKS: ...And put them on the stigma of the other one, the female part of the other flower.

BARBER: I wish our listeners can hear - see your hand movements.

SACKS: I know. I want to get the tweezers out and show you. Anyway, but - and then you hope for a seed, but usually, you don't get a good, viable seed. So what our colleague Duyan Tao did - he, at an early stage, around 10 days after the pollination, went in there and dissected out the very young embryo that was developing and put it in tissue culture and gave it nutrients to help it grow. And then he rescued one of these seedlings. And that was the beginning of it.

CREWS: Called embryo rescue.


BARBER: And what year was that?

SACKS: Oh, that was in the - 97.

BARBER: '97.

SACKS: '97.

BARBER: OK. So what has happened between that embryo rescue till now?

SACKS: So there's been a lot of selection. There's been a lot of crossing. And we did a lot of work to identify where in the genome were genes that affected how well the plant regrew. And then we identified molecular markers that we could visualize more quickly and easily to allow us to select those genes very quickly and find progenies that would give us the right combination of regrowth without the rapid spreading of underground stems, which we didn't want.

BARBER: So, Tim, how big is the scale of the crop that's happening right now in China?

CREWS: The latest numbers we have are around 15,000 hectares and 45,000 farmers.

SACKS: There's about 2 1/2-ish acres per hectare.

CREWS: So that shows how small the landholdings are of many of these farmers. They're measured typically not in hectares but mus, which is one-fifteenth of a hectare. So that also shows the scale of subsistence farming that is going on for a lot of this production. Not entirely, but yeah, so - but it's - what? - quadrupled...

SACKS: Yeah. Four times in one year.

CREWS: ...In one year. But it's important to realize that rice is subtropical. It's not frost-hardy, right? So it will not - people are like, well, can we grow it in Minnesota? And I'm like, well, you might grow it for six months in Minnesota, but it'll die because...



CREWS: ...It cannot persist through anything close to the winters that we have in these latitudes.

BARBER: How many times have you had this rice? How would you describe it?

SACKS: So I mentioned there are different cultivars that have been released. And they each have a different quality characteristic. So some are more fluffy, and some are more sticky. And so there's different types that we have.

BARBER: What do the farmers think about this crop? So the farmers that you've actually worked with in China - like, what is the consensus?

SACKS: So the main driver for the farmers who have been adopting it is they're really excited that it takes a lot less labor and a lot less money to produce the rice. As it turns out, rice farmers are a lot - in China, are a lot like farmers in in America. They're getting older. The young people are going to the cities for the jobs. And so anything that can reduce the amount of labor that's required to produce the crop is a huge advantage.

BARBER: So, Tim, what are the other grains or crops that you would like this to be a reality for?

CREWS: Right. So The Land Institute and many colleagues around the world are working on wheat, which is a similar cross between the existing annual wheat and a perennial relative. We're working on sorghum. But then we're also domesticating wild perennial species but with some modern tools of, like, genomic selection using DNA markers to guide the breeding process. We're developing a relative of wheatgrass called Kernza - it's in some beers and cereals - as well as silphium, which is an oil seed like sunflower. And then sainfoin is a legume sort of like a lentil. All of these are perennial. All of them build soil. They - it's not groundbreaking. It's ground-saving work. And yeah, I'd love to talk to you about it after the show here.

BARBER: And, Erik, I'm going to give you the last question. What is your dream outcome for the future of perennial grains?

SACKS: Oh, I'd love to see these crops further develop so that farmers all over the world are growing them and that we have a more sustainable agriculture where we're building soil, not destroying soil, where farmers are able to grow their way out of poverty, and we have a sustainable planet and a happy population, basically.

BARBER: I want to thank you, Erik and Tim. Let's give them a round of applause for coming to talk to us.


BARBER: One voice you didn't hear today but who was a huge part of this project is Dr. Fengyi Hu, dean of agriculture at Yunnan University in Kunming. He leads the team that studies, grows and harvests this new strain of perennial rice. And he was even kind enough to give the SHORT WAVE crew a sample of the rice. It was incredibly fragrant and super tasty. And we were told we were the first people, outside the research team, in North America to have this tasting experience.


BARBER: Before we go, we've had some staffing losses here at SHORT WAVE, and we're going to be in your feed three days a week now. It's going to be the same newsy, nerdy science content you love. And we appreciate all your support of our work. We love making the show for you. See you Wednesday.


BARBER: This episode was produced by Berly McCoy, edited by Gabriel Spitzer and fact-checked by Anil Oza. The audio engineer was Gilly Moon. Rebecca Ramirez is our managing producer. Brendan Crump is our podcast coordinator. Beth Donovan is our senior director. And Anya Grundmann is our senior vice president of programming. I'm Regina Barber. Thank you for listening to SHORT WAVE, the science podcast from NPR.

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