Thomas' Plant-Related Blog

On plant science. Mostly.

New crops: perennial grains?

with 6 comments

Most of our staple crops are annuals—plants that grow from seed, produce the next generation of seeds and then die, all in one year. In particular, the ‘big three’ crops, rice, wheat and maize, are all annuals. What would life be like if we instead grew perennials—plants that last more than one year? No more yearly ploughing and sowing.

Pear orchard

Pear orchard in the US. Photo by victorhansonsmith (flickr)

First things first: we’ve already got plenty of perennial crops. Many fruits, such as apples, grapes and kiwis, grow on trees and vines, and plants like the tomato can grow as annuals or perennials. But they’re luxuries, not our daily bread. The cereals and pulses that we depend on are almost all annuals.

There’s probably a reason for that. One might be that, because annual plants  have evolved to die after producing their seeds, they pour all of their energy into seeds, which are what we harvest. Another part of the equation is that ploughing the soil is a simple and effective way to kill weeds which might compete with the crop.

To keep it in perspective, though, the idea isn’t to replace the crops we’ve spent 10,000 years breeding. Rather, perennial crops may be able to produce food in harsh environments where conventional crops fare poorly—which could well be the parts of the world where they’re most needed. With larger root systems, they can use water and nutrients more efficiently, and by leaving less bare soil, they reduce water lost by evaporation from the soil surface.

There are also environmental benefits. Farmers growing perennial crops might allow more biodiversity to remain among them (think of the difference between an orchard and a wheat field), although that might be wishful thinking. The soil, left unploughed, will probably accumulate more carbon, while soil erosion and fertiliser running into rivers will be reduced.

Is it realistic? At a glance, yes: both rice and maize have close relatives (in the same genus) which are perennial, while wheat’s closest perennial relative, Thinopyrum, is a bit more distant. Nothing but a spot of cross breeding to do? Well, apparently both the US and the Soviet Union had a shot at it (with wheat) back in the 60s, and didn’t get very far. Perhaps the technology we’ve developed in the last 50 years—to read and understand genes, and then to alter them—can accelerate the process. Or maybe, taking a broader view of world crops, we’ll find a better starting point than wheat.

I’ll leave you with some numbers: the yield per hectare of four major annual crops and a selection of perennials. Some of the perennials do very respectably, although yield’s not everything.

Item Yield (kg/Ha)
Barley 2777
Maize 5109
Rice, paddy 4309
Wheat 3086
Almonds, with shell 1131
Cashew nuts, with shell 908
Chestnuts 3432
Cocoa beans 525
Hazelnuts, with shell 1241
Oil palm fruit* 14080
Walnuts, with shell 2400

* According to Wikipedia, this yields some 22% oil, giving about 3100 kg per hectare. (Data from FAOSTAT, for 2008)


Glover, J., Reganold, J., Bell, L., Borevitz, J., Brummer, E., Buckler, E., Cox, C., Cox, T., Crews, T., Culman, S., DeHaan, L., Eriksson, D., Gill, B., Holland, J., Hu, F., Hulke, B., Ibrahim, A., Jackson, W., Jones, S., Murray, S., Paterson, A., Ploschuk, E., Sacks, E., Snapp, S., Tao, D., Van Tassel, D., Wade, L., Wyse, D., & Xu, Y. (2010). Increased Food and Ecosystem Security via Perennial Grains Science, 328 (5986), 1638-1639 DOI: 10.1126/science.1188761


Written by Thomas Kluyver

28 July, 2010 at 11:02 pm

Posted in Papers

Tagged with ,

6 Responses

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  1. Seems to be a problem in units — The chart says 14080 kilograms of oil palm fruit, comment says the yield is 22% (implying 3098 kilograms), but then comment says this is 3100 tonnes… seems like it should be 3.1 ?


    29 July, 2010 at 1:24 am

    • My mistake! Thanks for pointing it out, I’ve corrected it.

      Thomas Kluyver

      29 July, 2010 at 10:29 am

  2. Thanks for this. There really been a lot on this topic in the literature lately. We’ve written on the subject here and also here

    Luigi Guarino

    29 July, 2010 at 8:18 pm

  3. […] perennial grains the answer? Thomas’ Plant-Related Blog comments on the possibility that perennial grains could produce crops in harsh climates, based on recent research published in […]

  4. Food is life. We have unvarying tendency to over produce profitable items due to our greed but under produce what is really needed. We have to replace greed with need. We should grow diverse perennial vegetation. Annual grain monocultures should be replaced with polycultures of perennial grains and oil seeds.

    Nalliah Thayabharan

    4 October, 2011 at 3:53 am

  5. Wheat raises blood sugar higher than most of the other foods. 4 slices of whole wheat bread raise blood sugar higher than 12 teaspoons of sugar. That’s a simple fact as per the table of glycemic index.
    Almost all wheat in USA is from a dwarf strain, which produces a far greater yield but has contributed to the current obesity epidemic.

    Nalliah Thayabharan

    18 June, 2012 at 1:23 pm

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