Does no-digging chaos still need crop rotation?

I don't dig, and all variety of plants are randomly placed with each other in no order.

I always read you need to rotate crops to minimise pests and diseases. This means the roots left in the ground would be harbouring them longer. And as everything's jumbled, I can't know what was where a year before.

Is crop rotation another practice some permies successfully ignore, or should I start practicing it like say brassicas to the west of my yard one year then the east of my yard the year later?

Does no-digging chaos still need crop rotation?  

The short answer to your question is:  Very likely not, especially considering what you wrote in that thread about your weeding strategy, I'd say your soil organic food web is going to take care of things for you, particularly as you progress with your system. I would probably say, tentatively that with permanent mulched beds, as you have, anybody will get consistently improving soil communities, and thus available nutrients, and will, as time goes on, need to think less and less about issues that people associate with crop rotation.

Crop rotation is primarily a tool for monocrop, or even micro monocrop, but it is more generally associated with and necessary with tillage cultivation.    Unless you are composting your feces and watering with your urine, you are bound to create deficiencies over time, especially if you are tilling, especially if you are creating large monocrops, and especially if those monocrops are planted repeatedly in one location.

 If, on the other hand you have permanent beds, and you plant large blocks of a single crop like beets for instance, and you decide to weed it perfectly, you get that one crop consuming certain organic and mineral nutrients, and when you pull all those beets, you pull a bunch of that out, and this could be bad if you have not build up your soil's organic matter well enough.  

But if you have plenty of soil organics in this no till beet monocrop,  the vast majority of the feeder root hairs that are attached to the soil food web remain in place, composting and building that community further, and I think you likely still get a net gain in terms of nutrients, but it is best not to monocrop.  

If you do small blocks of monocrop, and you put even a small amount of effort into thinking about it, it is unlikely that you will repeatedly overlap these patterns in the same place year after year, and that is really the only way that, with no till and a good soil food web, you will possibly get into big trouble with diseases and pests, in my opinion.  

As far as I can figure it, most diseases and pests are a problem created by damaged soil systems that are resulting from monocrops and tillage, and especially if they are combined, and super especially if they are not mulched, are weeded heavily with cultivation or outright removal.  

I always read you need to rotate crops to minimize pests and diseases. This means the roots left in the ground would be harbouring them longer.

 There are schools of thought that have people clear out all the dead matter above the ground in the hopes that this will eliminate diseases or pests that overwinter in them.  This, I believe, stems also from tillage agriculture where those stems would be tilled into the earth that fall or the next spring.  This completely unnatural pattern, of mixing in or burying a bunch of dry carbon rich material into the soil creates more problems with the soil food web (as it attempts to re-establish after tilling), then if it were left on top high and dry, and then in the spring were broken down to mulch, or left to stand and were planted amongst as if they are part of the topography.  

Primarily, I think this practice of cleaning out the garden of standing dead material arose out of a twisted sense of aesthetics.  This, I feel is more neurosis than it is intelligent, but again, that is my thinking on it.  That way of thinking does not appreciate that the skeletal remains of seed stalks can be beautiful snags that harbor beneficial insect larvae, such as lady bugs. (This is something that I saw as they came out in quantity from a two year old broccoli stalk that I pushed over).  Roots left in the ground do not harbor diseases unless you had a serious issue with the crop in the first place (and even then, in my opinion, the soil food web is likely creating resistance by you leaving everything in place)  [ It's probably best at that point to consider not putting that particular family of plants in that part of the bed for a couple years-but this is an extreme case--put a stake or two there with a flag on it, and a note in a book about what the flag means ], but some plant species roots do secrete exudates in the soil food web that inhibit certain other microbial communities and or other species of plants, and that can cause problems, again particularly if there are monocrops, and particularly if these are extensive, repeated, and you add tillage cultivation and don't mulch.  

But in your system, Tim, with chaotic plantings in permanent beds mulched with seaweed and leaves, with plenty of weed roots boosting the soil food web of your crop plants' communities... this is bound to be robust enough to take care of the majority of potential issues.  

everything's jumbled, I can't know what was where a year before.  Is crop rotation another practice some permies successfully ignore, or should I start practicing it like say brassicas to the west of my yard one year then the east of my yard the year later?

 I don't know how to answer that if I didn't already know what sort of stuff you are doing already.  I would say that in general, if you are planting brassicas all over the place, then you can continue to plant them all over the place, but only if you are also planting alliums all over the place, and cucurbits everywhere as well, and nightshades everywhere too, and beets and chard everywhere, and the carrot family everywhere and, and... well you get the picture... you are not going to get any harm by occasionally having a broccoli where you had a cabbage or kale the previous year.  

In my opinion:  Resilience is inherent in your system.      

I think we need to look at nature. In a natural system, an annual plant grows from seeds. Where do most of the seeds land? Immediately around the original plant, where they grow and flourish. Sure some get moved away, but if seed dispersion was essential (as implied by the rotation concept) there would be a lot less annual plants.  If annual plants needed rotation a lot of them would go extinct. If the annual plant in question does not grow in monoculture then the picture is something like what you are doing in a designed and deliberate way. Well done! The problem of course is in annual vegetables that have been bred so 'weak' that they might need special treatment, but the concept remains true.

I'm now convinced to just continue as I'm doing. Thanks.

Leaving the withered stalks to stand for years is interesting. I'd planned to chop and drop mine but I see the benefits of leaving them stand for years: shade, which Australian gardens desperately need in summer, and wildlife use.

I think we need to look at nature. In a natural system, an annual plant grows from seeds. Where do most of the seeds land? Immediately around the original plant, where they grow and flourish.

 This is true to a certain degree.  I actually quite agree with it, but I would add that in a natural system (which is hugely complex and I don't assert to have a massive knowledge base in all the directions of it's intricacies), most plants will come into an area and they will be superseded by others in time.  A weed has a certain job to do, whether it is producing biomass, or extracting a certain mineral or nutrient from the sub soil and bringing it up to the surface, and it will do this until it is done, or because it's own exudates had essentially 'poisoned' the ground for it's own species {but this happens over a long period of time, and only if conditions are such that succession to another plant species is not happening for some reasons}.  Successional issue can happen in desertified areas where shrubs take over, but trees have difficulty re-sprouting or otherwise regenerating because certain mega fauna (which browse or trample the shrub biomass down into the soil) have been removed from the successional process, so the dead branches, or whole dead shrubs are left high and dessicated, going through a very slow oxidizing break down instead of one in which microbes and fungi play a larger role.  

As mentioned, succession happens not only because the ground has become better suited to new plant species, but because the existing plant has sometimes fouled it's own nest with it's waste.  In this way, people who observe a natural field or meadow over time will notice that for many years an area might be dominated by a certain weed, whereas suddenly it has been succeeded by another one.  This even happens in gardens with tillage agriculture and intensive weed cultivation-over time, as fertility changes, and as a weed has done it's purpose, the weed species change, and it has been demonstrated (by attempting to introduce the plant back to the area) that the plant can no longer function in that soil system.  If one were to till that soil, it might be able to live there again, because the soil community would be knocked down to an earlier successional stage.

Many of our garden plants have been domesticated from weed varieties, and these above comments in this post can also effect them, but because, in the case of Tim's garden where their is a constantly changing chaotic mosaic of planting and weeds, it is very unlikely that this will ever happen (except with possibly some of the dominant weeds), especially since the vegetables have been selectively bred (whether intentionally or not)  to be able to withstand repeated planting in similar or same soils.

Leaving the withered stalks to stand for years is interesting.

 I've seen birds land on them, as well as butterflies, bees, and dragonflies.  Some animals will not land on the ground, but feel safe to do so on something raised above the ground.  Also this gives a space for web spinning spiders to find a place in the garden.  <--- {I know, considering the many extremely poisonous spiders in Australia that creating spider habitat might not be in your interest, though... }

If you have the room to crop rotate then what harm could come from planting your beets here this year and over there next year. No till has nothing to do with varying what needs this crop has and what that crop adds to your soil.

If you have the room to crop rotate then what harm could come from planting your beets here this year and over there next year.  

 no harm at all, but that is not what the OP  Tim  is asking.  He doesn't plant in mono blocks, but rather sporadic chaos, where crop rotation is functionally impossible, and in my view of things completely unnecessary.

No till has nothing to do with varying what needs this crop has and what that crop adds to your soil.

 I have a completely different understanding of what no till does.  

No till is a permanent soil system that is constantly building a soil food-web which gains (increasingly as it ages) plant soluble nutrients from the atmosphere and the mineral sub soil.  

No till is particularly enhanced with a maximized plant cover, (while ensuring that the choice plants have the space they need), plant species diversity, and plant shape (above and below ground) diversity, and mulching with a diversity of materials.  Compost is made much more effective in a system which is not tilled, if the compost is mulched over to protect it from drying out.   All of these factors can add different inputs to the soil food web, and as such, combine to make nutrients available to an individual plant.  

No till can also be enhanced with things like biochar being inputted via transplant potting soils or under mulch; and biological sprays or waterings, which can include things like actively aerated compost teas, diluted urine, or mushroom slurries, amongst other preparations.  While many of these things can be added in tillage cultivation, they are much more effective in a no till situation where the active biology is able to make use of it, or store it effectively with it's advanced nutrient holding capability, and otherwise stable systems of the living nutrient sponge like fungi.    

i agree i also like to add leaving plants that get covered in aphids or bugs at the end of there season
where there are thousands on 1 plant and in a week or 2
the pedators insects come  and you can see baby lady bugs and lacewings eggs everywhere and others i dont know

I just wanted to add a link to the referenced discussion in one of Tim's previous original threads. Do weeds rob soil of it's nutrients? just so people can make that connection, if they so choose.

In my experience, plants benefit from having legumes having been grown in the ground previously, as in a crop of field peas or beans covering the bed, but I have also seen excellent results have legumes interplanted with the crop plants in the same bed.  The latter can be done rather than rotating/cycling them as intensive blocks throughout the garden.     A few broad bean plants, for instance, go well almost anywhere (so long as they are not bringing too much shade to a plant that needs full sun), and a cluster of runner beans can climb a pole trellis that can be put up anywhere, and have plenty of other plants in amongst them, including plants that thrive in shade in the summer, including some greens and radishes.

Our human garden heritage encompasses many millennia, with the style of gardening changing and evolving to people's needs depending on location and, in more recent years, particularly in the west, the changing tides of technology and trends.  Polycrop planting has been successfully accomplished by traditional peoples all over the world, and is gaining popularity amongst permaculturalists and others who find that it's diversity enhances crop plants, if it's done right (meaning that the chosen crop plants still have the space they need to access light, moisture, and nutrients).  

I would be interested to see the region of South America where tomatoes originate, and where thousands of varieties are being grown with traditional methods.  In my experience traveling to indigenous villages, I would hazard to speculate that in the most traditional gardens in the smallest remote villages of the Andes, the tomatoes are grown in ways that closely approximate Tim's garden, or some variation of a more chaotic multi-cropping, rather than a planned rotation in blocks.

I don't know if Tim is growing tomatoes, but if he did grow a tomato, it would likely be mulched, it might have a weed near it, and maybe also a basil plant, a bush bean, and maybe some carrots, or some lettuce or spinach. It is unlikely that Tim's tomatoes, if he grows them, would individually be in the same spot from one year to the succeeding year, because his plantings, as he said, are chaotic.  Given that last point, that even in the unlikely event that a tomato plant happened to be same place as the previous year, the resilience of his intact soil system and nutrient rich mulch should be able to handle the tomato's problems, should they occur; Also, from what I understand of Tim's garden, the chance of a tomato plant occurring in multiple years in the exact same spot, seems quite remote.

I do not recall any mention of using hybrid plants in this or the previous thread.  I prefer heritage seeds, if I can find them, or any open pollinated varieties that I can save the seeds from.

Hi Scott Porteous.

i agree i also like to add leaving plants that get covered in aphids or bugs at the end of there season
where there are thousands on 1 plant and in a week or 2
the pedators insects come  and you can see baby lady bugs and lacewings eggs everywhere and others i dont know

 Bingo.   I think that you are observing the best of it, right there.  

The more we leave things alone (obviously within limits-->we are culturing this land), the more nature will take care of things.  The more we follow the natural cycles and patterns, and try to mimic them in our gardens, the more resilient our systems become.

Hi Tom, I'll chime in with my thoughts in an attempt to get this thread back to happier places.

I used to manage my garden with 25' rows of a single crop.  I lay them all out in excel so I can make a crop rotation plan.  Beans/peas precede tomatoes and other hungry crops.  Plants in general don't end up in the same bed for at least 4 years.  

Now I want to work my way to a more jumbled polyculture.  But I'm still stuck on the crop rotation thing so I divided all the beds in half so they are 12'.  In my program I shifted the half beds so that they don't line up with their partners any more.  This probably sounds confusing but instead of having row #1 be 25' of tomatoes, now the South half of row 1 is tomatoes and the North half of row 7 is tomatoes.  Next year it will be rows 5 and 11 since I jog them 4 rows over each year.  

So this at least gets my monocrops to be only 2.5' wide beds, 12' long.  Any volunteers are left to grow and some weeds.  I'm not sure I'll ever get totally polyculture since it's so hard to manage 200 garlic bulbs over winter along with trellis requiring beans and tomatoes, space needing squash and early crops vs summer crops.  Today I picked two gallons of beans from my two half rows of green beans.  If they were sprinkled around on individual trellises they'd cast more shade in different places and they woudn't support one another.

So I'm in your boat but I'm managing it in one "conventional looking" garden.

One area of polyculture I'm interested in is how to seed it. I tend to grow in polyculture but it is really just micro clumps of the same type mixed with other micro clumps. Do you mix a bunch of seeds together and broadcast? Or plant them individually? I also tend to have issues of the plants being way to crowded when I just broadcast them...

I feel your pain Daron.  When I plant carrots in little rows I get 20% germination.  This year I got frustrated and prepared a whole 12' bed and broadcast a thousand carrot seeds.  Then I scuffed it with a rake gently and covered the whole thing with 1/2" of sifted compost.  Bang, tons of seedlings.  It took 40 minutes to thin but now I have a full bed of carrots.

I can see how poly planting works well with transplants.  With seeds it seems like you need to deliberately seed them in spots or just wing them around and let a lot of them not thrive.  But I'm sure many, many other folks have figured it out and are just snickering at me.

One other thing I did last year was grow beets for seed.  Once I harvested the seed (tons), I took the smaller seeds and just sprinkled them in beds that would have larger plants or single rows in them this year (tomatoes, beans, etc.  I hoped I'd have tons of beet "weeds" to thin and let grow wherever.  I think about 7 of them grew.  Better than nothing but not worth writing home about.

Daron Williams wrote:One area of polyculture I'm interested in is how to seed it. I tend to grow in polyculture but it is really just micro clumps of the same type mixed with other micro clumps. Do you mix a bunch of seeds together and broadcast? Or plant them individually? I also tend to have issues of the plants being way to crowded when I just broadcast them...

Overcrowding isn't a problem if the plants are compatible and you have luck on your side. Eg. My baby endive lettuce grows well with rocket/aragula, spinach and weeds in the same spot. The endive lettuce and weeds are low growing and need minimal light, spinach and rocket grow high above it, so there's no competition for light. I did it with no planning, just planted the seedlings next to each other.

But the combination in another spot doesn't work, which is why I say luck plays a role too.

Tim Kivi wrote:

Overcrowding isn't a problem if the plants are compatible and you have luck on your side. Eg. My baby endive lettuce grows well with rocket/aragula, spinach and weeds in the same spot. The endive lettuce and weeds are low growing and need minimal light, spinach and rocket grow high above it, so there's no competition for light. I did it with no planning, just planted the seedlings next to each other.

But the combination in another spot doesn't work, which is why I say luck plays a role too.

So you are transplanting not direct seeding for your polyculture beds? My overcrowding mainly comes from direct seeding - I had a fun crazy bed that was very much a polyculture that I transplanted small plants into and they all did great. Looked like a jungle but no real issues. But my broadcast attempts have not worked great so far.

Been thinking about mixing in some dryish soil with the seeds and separating the seeds out based on size. Then broadcasting each mix individually with the soil mixed in to help ensure they spread out. Could combine it with worm castings or compost and just get two tasks done at once I would love to develop some seed mixes that I could easily broadcast that would contain leaf crops, root crops, fruiting crops, etc. Then let the plants sort themselves out a bit. Not there yet...

Your polyculture looks great! I also like to mix in a few perennials in my polyculture beds around the base if they are raised beds and sometimes mixed in depending on what they are. Things like Good King Henry can be mixed in but I like to put lupins on the edges or spaced out widely for some nitrogen fixing and for beneficial insects.

Mike Jay wrote:I can see how poly planting works well with transplants.  With seeds it seems like you need to deliberately seed them in spots or just wing them around and let a lot of them not thrive.  But I'm sure many, many other folks have figured it out and are just snickering at me.

Well those people need to come in here and give us their secrete! I'm thinking about making some experimental beds where I can test different polyculture seed mixes to slowly figure out what works and what does not...

If it's overcrowded and they're not growing as a result, just pull them out gently and transplant them elsewhere! This is what happened when I transplanted my excess baby endive seedlings to a new spot and they grew up

Growing fro seed in situ works well if you cut all your plants down at the same time so that the seeds have enough light to grow. If you have mulch and tall plants already they won't get enough light to grow up. All the photos I posted are of seedlings planted on completely bare soil a few months ago.

Tim Kivi wrote:If it's overcrowded and they're not growing as a result, just pull them out gently and transplant them elsewhere! This is what happened when I transplanted my excess baby endive seedlings to a new spot and they grew up

Growing fro seed in situ works well if you cut all your plants down at the same time so that the seeds have enough light to grow. If you have mulch and tall plants already they won't get enough light to grow up. All the photos I posted are of seedlings planted on completely bare soil a few months ago.

But I'm wanting to be lazy and just broadcast seeds and not have to deal with transplanting

But I'm wanting to be lazy and just broadcast seeds and not have to deal with transplanting

 So in this case, I figure that what you need to do is focus on seed production first, so that you can put a volume of seed out there.  That is really a big portion of the ticket when it comes to broadcasting.  I went to a Permablitz 4 and a bit years ago at the Darfield Earthship, which was being guided by two permaculture teachers, including Javan Bernakevitch, who studied with Sepp Holzer.  In that workshop he focused on putting out volumes of seed, which in that case he and the other instructor Gord of Element Eco Design, had been given a lot of old seed from seed companies in B.C..  The crops and seeds were broadcast over a large hugulkultur we built, but the seeds were also patted in or pressed in with finger tips.  Then the whole surface was covered to about 50% with straw, to hold the soil and moisture in place until the young plants could stabilize the system.

In Toby Hemenway's Gaia's garden, he talks about polyculture broadcasting.  He specifically mentions broadcasting same size seeds in one handful, rather than say, corn and squash at the same time as arugula and carrots.  If you Broadcast the larger seeds together, the seeds will disperse evenly; and likewise with the smaller seeds.  Javan, if I remember correctly, said that broadcasting takes some time to develop the technique of evenly dispersing the seed, but that, like most skills, it becomes easier the more you do it.

I for my part have mimicked a practice of some local larger scale organic farmers in this valley, Gary and Wendy Lowe of Twin Meadow's Organics.  They use a planting board, which is made by taking a chunk of 3/4 inch plywood, and drilling it halfway through at 2 or 3 or whatever inch spacing, and then cutting two inch dowels, and putting glue in the holes and pounding the dowels into the holes.  Two sets of holes are cut through on opposite edges of the board, and a rope is strung through each set, so that there are two long loops.  The board is set on the bed, and is stepped on, pushing the dowels into the bed.  The loops are used to place the board, and to lift it off the bed from the path, so they have to be a comfortable length to do so. Then the board is moved down the bed adjacent to the spot that was just done.  While the board is in the second location, I kneel on the board and plant some seeds in the previous holes of the first location, as well as accessing the paths on both sides over the board.  I have a mix of seeds in a bowl and choose where I want to plant the seeds, depending on species (which I have a general idea of by seed shape knowledge).  

This method amounts to using a lot less seed, and having a really good spacing, and does not take that long considering the lack of weeding that needs to be done because of the density.  Sometimes I have a 'sacrificial' crop, like spinach, which I also eat, and it is planted in every second hole, while a crop of kale and collards is in the alternates.  The crops get thinned after they've provided quick greens, leaving choice largest plants to produce into full size.          

Crop rotation is a "solution to monoculture farming" because we didn't want to do polyculture farming.
It sounds like you are already doing polyculture so you are mostly alright.

That said if your "polyculture"  is 80% carrot with a few onions and bush beans. I would still recommend to that you switch out the carrot to another plant ever so often.

all successful natural farming, and no-till/dig methods are basicly methods of enhancing the soil food web.

So the answer is no, crop rotation is unnecessary, and in fact the more you grow the same variety ofcrops in the same place the better because the soils microbiological community will more and more adapt to the environment conditioned by that variety of roots.

the reason crop rotation is necessary where digging and tillage are the culture is because it destroys the foundation of the soil food web and all the networks and biofilms that have formed over the ages. Those sorts of networks that are geared toward plants do not reform in soils amended with fertilizers, organic or not.

I often use the acorns as prime examples of the natural process out performing humankind's abstract, & fundamentally delusional  methods of food production.

a thriving acre of acorn trees (oaks) on a good year can produce 6,000 lbs of nuts. They is 3 times what any nut farmer in California produces on a good year.

Not only do acorns grow that we'll without any inputs or cultivation , but that same acre has been doing so without any cultivation or crop rotation for eons and eons simply because there is carbon to support the soil food web and because the soil and the microbial networks are left undisturbed.

UC Davis wrote:Yields.  Annual yields for walnut varieties are measured as clean, dry, in-shell pounds per acre.  The average yield over the remaining life of the orchard is assumed to be 5,400 pounds per acre.

https://coststudyfiles.ucdavis.edu/uploads/cs_public/de/5b/de5b047e-efb5-4145-b618-1c643240abe9/walnutsv2012.pdf

that's in shell.

pine nuts yield 5,000 lbs in shell and 250 per acre out of shell

once you factor the shell weight of those walnuts the yield will be closer to 2K just lik I said

Table C. Annual Yields
Yield (dry, In-shell)
Year ton/acre lb/acre
4 0.25 500
5 0.50 1,000
6 0.75 1,500
7 1.40 2,800
8+ 2.70 5,400

Not to mention how much fertilizer they use goes up every year along with general costs of all the cultivation required.

what is the average life span of a cultivated walnut orchard in California before having to replace the trees because they stop producing?

Acorns and pine trees produce more and more as they get older, also unlike orchard trees in that respect.

Tips about Polycultures from Toby Hemenway's Gaia's garden in my own words...  

Seed several varieties of each species (imagine, for instance, an example of lettuces that are planted at the same time, but go to full head, or bolt to flower, at different rates.  This, especially if you have familiarity of what each species looks like in the first place, gives you tons of information on how these species will act in polycultures, and occupies more ecological niches, while stacking the lettuce function in time, lengthening your harvest).  

Don't sow seed to thickly. Check seed packages at your store or look online for the planting density of a given seed, and then, if you are for example going to sow 10 varieties in one bed, then only seed out 10% of what it says on the packages for each type.  Unless you want to do the heavy broadcasting and transplanting method of Tim (which is awesome.. I follow this technique as well, sometimes) then you might find that any more than one seed on the soil (and then covered with dusting of compost or top soil), per couple square inches is plenty. By not overseeding too heavily you will get better performance from tender young herbs like dill and flowers like calendula.

Harvest greens early and in some instances heavily to open up light and space for other plants.

Mix your families, not just species within families.  Mixing families in the bed confuses pests that might infest say in a bed planted and dominated by cabbage, kale, broccoli, cauliflower, and Brussels sprouts which are all in the brassica family.

If you want to cover the soil and get things rocking fast, then do have a heavier thicker coating of seeds of  plants with shallow rooted fast growing nature: radishes, mustard greens, fenugreek, and buckwheat.  Eat them young and enjoy the bounty of flavors, and then transplant into this.

Overlap harvests:  In the same places or beds that are dominated by say dill in the spring, can be dominated by basil in the summer.  Consider this in all aspects, so that you can stack functions in time.  

Avoid root and light competition:  Think about the nature of each plant, does it have a sprawling nature above or below ground, or does it have a pointy root, or a tall thin nature? How will these effect other plants?  A potato is difficult to plant with other plants, but can be surrounded by a quick crop of leaf lettuce and radishes before it gets bigger and needs hilling. A dill plant can grow above the sprawling nature.  Consider that some plants enjoy shade, and others do not.  Some plants like potatoes and some squash plants, can be partially buried and seem to enjoy the climate, rooting into it!  

Save a few plants for seed:  Let a few choice plants go to seed.  What I like to do is put a stake and ribbon of cloth beside a plant (say the largest, healthiest, Kale seedling), and do not harvest anything from it at all (even though it's really tempting).  Let it grow to it's full potential in root and leaf and take over the largest area that it can, and then let it go to seed.  The more you give this plant what it needs without pampering it too excessively, the better the quality of seed will be in regards to your system.  Once the seeds are formed, consider knocking it over a bit towards where you want the seed to drop, or harvest the seed for next year's (or an autumn) broadcasting.  Toby recommends choosing plants on the poleward side of the bed, if given a choice, so that the tall seeding plant does not block sun. I think that this would depend on how many plants you have going to seed, and how big your garden is.  If in the case of a biennial, you will know to plant a bunch of shade loving plants on the poleward side the second year.  

Examine your polyculture often, daily if possible.  This will grow fast and dense and will need your harvesting prowess, and the reward is constant salads and stir fries.  As the Chinese say: The best fertilizer is the gardener's shadow.

Toby also recommends harvesting whole plants, meaning to pull out a plant, root and all, to give space for other plants.  I personally think that cutting them at soil level is a better technique for preserving soil life, but many might try to re-sprout from the cut root.    


 

I'll add that if you plant an area with the right mix of plants, which are naturally resistant to pest destruction, you've now achieved permanent agriculture. They self-seed in the same area, insects balance each other, and the cycle takes care of itself. I've seen it work on a very small scale with a forgotten herb garden where after 20 years the same herbs are still self-seeding in the same spot without any assistance.