Annuals, Perennials and Permaculture

I posted a while back on the issue of annual and perennial plants and the permaculture movement. An interesting debate on the Permaculture Research Institute of Australia website initiated by Angelo Eliades has prompted me to reflect further on the question.

Other than confirming once again that the Y chromosome finds ever new arenas in which to construct its fragile ego, the debate turns on the possibilities for replacing the widespread cultivation of annual plants in global agriculture and horticulture with perennial plants. As explained in my original post and as further outlined in Eliades’s article, the potential benefits of doing so are multiple. The question is whether it’s possible to provide enough nutrients – particularly macronutrients such as energy and protein – to the planet’s vast human population with a purely perennial agriculture.

It’s striking that most wild floras are dominated by perennials, whereas most agricultural crops including the major staples are annuals (wheat, rice and maize provide the majority of global macronutrients). But there are some perennial staples – mostly tuber crops such as potatoes, yams and cassava, although very often these are cultivated as if they’re annuals, thus losing most of the environmental benefits of perenniality. It’s also worth pointing out that since the Neolithic revolution, most of the world’s population has been fed by annual grain agriculture including all of the famous ancient civilisations, with tuber/perennial-based systems dominating in only a few areas such as New Guinea and parts of sub-Saharan Africa (see, for example, Mazoyer & Roudart A History of World Agriculture or Mithen After the Ice). But though relatively rare, these tuber-based systems have proved stable and successful.

Now, an important permaculture principle is to model human landscape design after natural systems, and since perennial plants are so dominant in the wild this alone is enough to make many permaculturists favour perennial-based cultivation. The puzzle then is why it’s proved so relatively rare in human agricultural history. Eliades believes, first, that perennial plants are more productive than annuals, while simultaneously requiring less energy and effort to grow, which would make the puzzle all the greater if it were true. His answer is that, second, the only reason we plant annual crops is because of “arrogance and lack of perspective”.

Both of these claims are so absurd that they shouldn’t really require any refutation. To fabricate a cultivation system that conjures additional productivity out of nothing, while simultaneously  dishonouring the many annual-based farming cultures that have laboured to create viable social ecologies takes a lot of cheek, and is the sort of thing that prevents the wider world from taking permaculture as seriously as it should. OK, perhaps I should register one slight qualification here – as I mentioned some time ago in my post on potatoes, it’s possibly true that grain-based agricultures better suit the interests of state-building elites than tuber-based horticultures (though I very much doubt it’s really that simple), so in that respect perhaps there may be a small role for ‘arrogance’ in the development of annual cereal culture, but not nearly enough to explain its ubiquity.

So we’re back to square one with the puzzle of annual agriculture and perennial flora. In my earlier post, I mentioned Professor J. Philip Grime’s CSR theory as a way to explain the puzzle. Grime classifies plants as ‘competitors’ (selected for in high nutrient – low disturbance situations), ‘stress tolerators’ (low nutrient – low disturbance) and ‘ruderals’ (high nutrient – high disturbance). Most wild habitats are low nutrient, low disturbance and are characterised by stress tolerator perennials, with slow growth rates, cautious reproductive strategies and defences against herbivory, all of which tend to make them less appropriate for domestication in terms of yield and possibly palatability.

As Paul Hillman pointed out in a response to my original post, and as Angelo Eliades also points out, there are nevertheless quite a number of highly productive perennial crops such as sugar cane, cassava, plantains, potatoes etc. With my thinking clouded by the perennial vs annual distinction in the context of CSR theory, my initial response was to suggest that these crops were probably less productive than the annuals. Quite how productive they are in terms of yields per unit fertiliser input or per unit solar input in comparison to the major annual crops is something I need to work on some more, but I’ll now readily accept that they might well compare favourably. Because on reflection, the broader point about all of these perennial staples is, I suspect, that they fit naturally into the ‘competitor’ category of high nutrient/low disturbance crops – essentially pioneer plants that quickly occupy and crowd out fertile space (think of the way gardeners describe potatoes as a ‘cleaning crop’, for example) before giving way to stress tolerators in long-term succession. Many woody fruit and nut species also occupy the competitor or competitor-stress tolerator hybrid niches, as Grime has remarked. In this respect, perhaps we can place the three strategies on a continuum of agricultural usefulness (yield and perhaps palatability) from R to C to S. And if we map the annual-biennial-perennial distinction onto that continuum we’ll find most of the annuals and biennials and a few of the perennials at the R/C end of the spectrum, and most of the perennials at the S end.

That, at any rate, is my working hypothesis. It explains why agriculture and horticulture tend to favour R and C strategists and invariably try to prevent ecological succession (by ploughing, mulching or burning), and this in turn explains why our cultivated plants are mostly annual and biennial but with a number of important perennials.

All of this matters because C strategists – whether annual or perennial – are essentially short-lived, high nutrient demanders, so they don’t exempt us from the fundamental agricultural tasks of generating fertility and preventing succession. This shouldn’t be all that surprising, because in the spartan energetic economy of nature, nobody can expect a free lunch. The more we try to push productivity, the more we need to fertilise and curtail succession, and the more perennial agriculture starts to resemble annual agriculture (eg. with sugar cane replanted every second year in high output systems). And unfortunately we do need to push productivity, because there are 7 billion people on Earth. I think it’s worth being a little sceptical of anyone who claims to grow all their own food, and even more sceptical of anyone who claims to grow it all from perennials – which is not in any way intended to suggest that I think it’s a bad idea to try. There’s much to be said for abundant polyculture, but we do need to keep an eye on overall yield and energy balance. In that respect, every step towards a more perennial staple agriculture and horticulture is important, and initiatives such as the Land Institute need our unqualified support. But the ultimate goal of a productive perennial agriculture is not an easy one to achieve – to state otherwise on the basis of a simplistic reading of permaculture principles risks discrediting the movement. There’s already far too much snake oil on sale.

I have a lot more work to do to flesh out this basic thesis, but I think that’s enough for now. I’d be interested to hear anyone’s further thoughts on the topic.

10 thoughts on “Annuals, Perennials and Permaculture

  1. I thought you had hit the nail on the head chose the words “agricultural usefulness” as the baseline against which to map the RCS continuum. I do how ever think that you should expand the definition of usefulness beyond yield and palatability to include agricultural and cultural utility and that these should be in block capitals. It might be helpful to look at the fate of a couple of perennial agricultures to explain what I mean.
    1/ Fruit is almost exclusively grown on perennials and we have found many ways to make them conform t0 our needs which have little to do with simple yield. I haven’t time to start listing them but it’s worth pondering and if we didn’t need them for nutritional and cultural reasons I suspect fruit would have dropped out of agriculture long ago being too problematic. Interestingly the largest volume fruit in world production is a perennial grown as an annual the tomato. Is this because it is the highest yielding, most delicious or nutritious? I don’t believe so. I have visited tomato growing operations in Italy where the tomato is grown in rotation with cereals. Could it be that it is the ability of the tomato to fit within an established agricultural system is the reason for its ubiquity? If this reasoning is projected back into agricultural history it is possible to develop scenarios where utility was equally important to yield.
    2/ Coppice wood was being used for fuel and building materials at the time of the earliest farmers in the UK but fell out of favour when it was first over used and then replaced by coal in the industrial revolution. But biofuel is back but not in the form of old style coppice, why not? The answer cannot be given purely in terms of yield.
    As an aside – Why is sugar cane grown at all let alone made it to the top of the pile amongst agricultural crops? From and energetic point of view it looks good but nutritionally it is a poison when eaten in large quantites. I have stats which say 20% of the average American diet is sugars of one form or another. All at a time when the worlds 7 million need feeding. You cannot easily exclude economic and political reasons for agricultural choices.

  2. Thanks Paul for another thoughtful response. I’d like to follow up on a few of your points, but will probably leave them for now as they’re relevant to my next post. What I’d say now is that I certainly don’t think yield (ie macronutrient production) is the only important consideration. On the other hand I probably am inclined to think that it is the most important consideration, because I think it’s the hardest thing to produce in sufficient quantities in a sustainable farming system. If you tell me that it’s equally difficult to produce the many micronutrients and other things we need, then I’ll believe you – and that’ll mean that our future problems are a whole lot more insoluble than I’ve been imagining.

    I’d say that biofuel isn’t back in the form of old style coppice for the same reason that organic food isn’t back in the form of old style small mixed farming – labour costs and industrialised regimentation.

    Totally agree that there are economic and political reasons underlying agricultural choices. But I don’t think they trump biological reasons long-term, at least not in the context of a solar ecology. Or to put it another way I don’t think people have focused so single-mindedly on annual cereals for 10,000 years because they forgot to look at perennials.

    • So both the coppice and old organic agricultural set up have gone out of favour and returned in a culturally mediated form in a shorter time period than it would take to do a useful perennial breeding program. We may think we are a clever species but we are utterly hopeless at long term planning. I suspect that perennials were looked at and used a lot (you talk as though they are gone) but as a greedy and opportunistic species we would tend to favour plants which allow this behaviour. Perennials which are now grown as annuals will have gone through long periods of our relationship with them being grown as perennials. I am not trying to make the point that yield isn’t important I just believe that other process were at play during agricultural development that meant a cool decision making process choosing the highest yielding possibilities is unlikely to have been the way things were. Speculation of course.
      Incidentally if I had to design a Decision Tree to help someone develop an agricultural system the first question would be “what are the nutritional requirements that the new agriculture are aiming to deliver?” Second question “what are the available agricultural practices that are capable of producing food of the appropriate quality?” And now “what is the most effective way of producing that food using those methods?”. The answer would not be what we have now.

  3. I think I agree with what you’re saying inasmuch as our greed and opportunism has led us down an agricultural path of choosing particular sorts of crops which has enabled a huge population explosion but which is unsustainable and has now put us into a big hole. I don’t think perennials are ‘gone’, but nor do I think it will be a simple matter to get out of the hole by switching to perennial agriculture. Where I think we disagree (which is where I think we usually disagree) is what we do from where we are now, and I do strongly believe that any overall solutions we try to adopt have to aim overall to provide fully for the current and future global human population otherwise they will be both self-defeating and unethical. I wish it were otherwise but what I wish is neither here nor there…and neither you nor I are in a position to point the finger at other people in relation to over-population!

    Anyway, I’m now going away for a few days – I’m driving to Edinburgh to give a conference talk entitled ‘Agro-ecology: securing sustainable futures?’ and I hope to enjoy the opportunity of debating with you the many contradictions implicit in this little odyssey upon my return…

  4. I may have missed something, Chris, but with the words, ‘… perhaps we can place the three strategies on a continuum of agricultural usefulness (yield and perhaps palatability) from R to C to S. ‘ aren’t you making a bit of an assumption? I mean by putting R before C. You don’t seem to have established any reason for doing that – other than your overall desire to champion annuals. But, as I say, I may have missed something.

    I feel your central argument, that humans would have switched to perennials at some point in history if they really could produce as much as annuals is more of an assertion than the clinching argument which you seem to hold it to be. On the contrary, I feel there’s plenty of evidence to suggest that humans tend to be good at addressing immediate, short-term situations but shy away from addressing issues with a longer timeline – eg breeding improved perennial crops.

    This tendency is clearly one element in the present consensus on climate change, which has moved on from denial to an acknowledgement that it’s happening combined with a decision not to do anything about it. Of course the question of our response to climate change is a complex one, but a discounting of anything with a long timescale seems to me to be a very important component. When you suggest that humans must, at least at some point, have done the sensible thing I think you’re on shaky ground. Present experience suggests the contrary.

    In fact my position isn’t that perennials are more agriculturally useful than annuals. I suspect that, if they had been given the plant breeding that annuals have received over the past 10.000 years, they would be about on a par. What i do contend is that they’re more ecologically sound and if they really are equally useful agriculturally then that’s the direction we should go.

  5. Thanks for that Patrick – very informative comments of the kind I hope this blog can stimulate.

    A couple of points by way of reply:

    Yes, you’re probably right that it’s not really a continuum of RCS so much as RC/S or CR/S. Sloppy thinking on my part, quite possibly. Maybe I was implicitly assuming that there’s likely to be an inherent yield advantage amongst the ruderals given a high fertility situation on the basis of their lifecycle strategy, but such an assumption may not be warranted – as you’ve pointed out before there are certain advantages to perenniality as a starting point for seasonal growth. Of course, high yield is a questionable advantage in terms of the vicious circle of forcing agricultural productivity anyway, but that’s another story…

    In relation to agricultural history, at this stage I only want to put my arguments forward as a hypothesis. I certainly don’t think I’ve clinched any arguments, but I do think these are arguments worth having in view of some of the more extreme statements doing the rounds amongst permaculturists about the benefits of perennials and the wrongheadedness of annual agricultures. I agree with you that the human selection of choices (and indeed the natural selection of species) are strongly geared towards present expedience, something that current inaction on climate change exemplifies only too well. The question is whether that explanation alone suffices to account for the preponderance of annual over perennial agricultures historically. I’m not sure that it does. It’s true that this is largely a conjecture on my part which requires substantiation (though perhaps the same is true of the alternative view?) – I’ll try to come back to this with more data in the future. It does seem to me, though, that there’s a strong but subordinate perennial component in a lot of agricultures historically, involving quite sophisticated modification of the original stock, which I think is at least suggestive of the possibility that perennial agriculture has its limitations.

    It seems to me that with both annuals and perennials, but especially with perennials, we probably have (and have had historically) quite limited options with which to work. Perhaps, moreover, those peoples who figured out relatively sustainable, perennial-based agricultures tended to lose out historically, either to other peoples sustaining denser populations on annual agriculture or to the vulnerabilities of their own systems under population pressure, as in Geertz’s analysis of Indonesian agriculture. By that, I don’t mean to suggest that annual agriculture is superior, not least because I agree with you that it’s less ecologically sound. But it might imply that it’s not so easy for perennial agriculture to match annual agriculture on productivity grounds – and it does seem to me that the logic of pushing the productivity of perennial C strategists is that we may end up with a perennial agriculture suffering from many of the same ecological drawbacks as annual agriculture.

    Anyway, these are all contentions that require further substantiation on my part. And I agree with you that we should be aiming towards a sustainable perennial agriculture if we can. I suppose the main point of my post was to suggest that that goal may be harder to achieve than is sometimes imagined. But thanks for your thoughtful challenges to my assumptions, which I’ve found very helpful. I’ll try to come back to this again at a later date.

  6. Have you read Mark Shephard’s book, Restoration Agriculture? A must rewd in this discussion. He’s got a 105 acre commercial perennial ecosystem, growing more nutrition per acre than annual crops. Lots of data. Be curious about your thought after reading. Cheers.

  7. This philosophical controversy is far from reality.
    In practice, all civilizations (including traditional farmers and permaculture cultists) grow both types of plants.
    The yield of annual plants is greater than that of perennials, but not much. You can feed all 7 billion people with perennial plants and stop global warming.
    The most productive plants in cold climates according to scientific data:
    Columnar apple tree 115-400 tons per hectare (the most productive plant in the world, moreover, perennial! Permies are right!))
    Sorrel 60 tons per hectare (I can’t believe it! More sorrel to the forest garden!))
    Quince 50 tons per hectare (Quince is not tasty! But you have to eat it to save planet!))
    Gledicia 45 tons per hectare
    Grapes 40 tons per hectare
    Jerusalem artichoke 40 tons per hectare
    Apricot 30 tons per hectare
    Cherry plum 30 tons per hectare
    Cabbage 130 tons per hectare
    Zucchini 130 tons per hectare
    Watermelon 110 tons per hectare
    Cucumber 100 tons per hectare
    Tomato 100 tons per hectare
    Carrots 90 tons per hectare
    Beets 90 tons per hectare
    Chard 85 tons per hectare

    • Yep, but most of the weight of fruit & veg is water, so really you need to look at the per acre yields of the nutritional indicators of interest – energy, protein, vitamins, minerals or whatever. And the yield depends on geographical location.

      Since I wrote this post, I’ve published a lot more on the annual/perennial issue – see the relevant page on this site. I’m not inclined to revisit the issues here, but yep agreed that we need a mix of perennial and annual plants. What I’d suggest we don’t need is people saying that there’s no place for annual plants in agricultural civilization…

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