Pit and Mound Gardening

Hang out in sustainability circles for any length of time and you will notice a distinct antipathy towards traditional vegetable gardening. It ruins the soil; it is dependent on inputs; it eschews perrenial plants. It is un-natural. And in most cases that is all true.  But there are some real truths that this attitude can gloss over.  First, annual vegetable gardens are wicked productive – easily a pound or more per sq ft.  Second, the vast majority of us are used to eating food grown in annual vegetable gardens and food habits are extremely difficult to change – they are a integral part of our living culture and that changes slowly;  I am much more likely to eat potatoes than skirret or sunchokes, no matter what the permaculture books tell me.  Third, its gonna take YEARS for your multi story permaculture forest garden to start producing much of anything.  For certain, eventually it will outpace your annual gardens in productivity, but that is a decade or more out.  Until then, the 25#’s of harvest per tomato plant is gonna make you and your larder a lot happier.

So whats a suburban homesteader to do?  I’ve read thousands of pages on sustainable vegetable gardening – fantastic books from John Jeavons, Elliot Coleman, and many more that have inspired and intrigued me to the possibilities of vegetable gardens.  I’ve also read thousands of pages on ecology and soil science that contradict so very much of what those masters and mistresses have to say; tilling is very rough on the soil.  I want to have healthy soil, but I also need and intend to have a large canning garden for years to come.  Mulch Gardening like Ruth Stout’s “No – Work” garden and Lee Reich’s Weedless Gardening makes a great step towards integrating the two philosophies by removing much of the tilling.  Word to the wise though on this – Ruth Stout gardened conventionally for over 7 seasons before switching to no-till.  It takes a long time to build up your soils and you also need to irradiate persistent perennial weeds like quack/couch grass, sow thistle, and the like if you have them on site.  No till gardening is a journey, not a destination!

Bolstered by some impressive results from 2009, I mulched heavily this year and was very impressed with the reduced weed and irrigation inputs.  But the garden was still flat and that bothered me.  So at the market garden I tried a new technique that I want to explore Whole Hog in 2011.  Essentially it is based on a side bar blurb in Chapter 12 of David Blume’s epic opus Alcohol Can Be a Gas. Now a book on homebrewed energy revolutions is not a place one would expect to have an epiphany on vegetable gardening, but David is a die hard permaculturist so its all connected.  His idea was to dig trenches under your paths, fill them with mulch, and then use these mulch paths to breed up trillions of red worms to function stack a “wasted” space in the garden.  This idea worked wonders at the farm – with the beds I used this technique out producing my conventional beds by 20-50%.  As the season went on, I gave it more and more thought and always paid special attention to those two beds – digging and poking around as I tended to them.    My findings in short were these:

  • Mulched Trenches improved drainage -essentially turning the planted areas into raised beds
  • Mulched Trenches improved water retention – the mulch acted like a sponge, holding water for weeks and weeks between rains keeping a higher water table within reach of the annuals
  • As hoped, Mulched Trenches foster just ridiculous amounts of fungus.  My hope was that even with the soil intrusion in the beds from potato harvest the fungus would live on in the paths to re-innoculate the soil for the next season.  The mycelium was often inches thick and brilliant white to the naked eye.  Bingo!
  • Thanks to the moisture and fungus, the Mulched Trenches are havens for earthworms, even if you don’t plant worms in them, they will be there soon enough.
  • Within only 3 months, a 1/8″ (3 mm) layer of humus formed under the straw that mulched the potatoes and was clearly evident to the naked eye when harvesting.  That is very impressive soil building in such a short time.  Now, this was on incredibly microbially rich soil that has been farmed organically for 20 years so your results may vary, but it is no wonder why straw mulch gardening works.  You are truly “uppening” your soils!

All of this really coalesced with the epiphany that  my Mulched Trenches essentially mimic “pit and mound” topography in old growth forests and were creating all kinds of interesting micro climates for soil fauna and plant roots to exploit.  Wait a minute – the reviled and ecologically barren annual vegetable garden was starting to sound a lot like permaculture!  I was on to something.

With that in mind, I set out to integrate these learnings into my freshly “pimped out” garden as I prepped it for the 2011 season.   The layout will be a 1′ Mulched Trench on each side of 30″ growing beds.  Now that is a lot of path, and purists will give me hell for that.  Whatever!  To manage a 1100 sq ft garden, be a husband, father, and still work a full time job and do all my other projects if I can’t get into my garden easily and efficiently it will turn into a mess faster than you can say “fundamentalist”.   I plant in straight lines – it may not be efficient in space, but it is incredibly efficient in time and labor – we need to factor those things into our plans too.  Mandalas are great, but they’re not for me.  While digging the trenches the soil was piled up onto the 30″ growing beds – mimicking a “double dug” bed.  On top of this I applied .5-1″ of compost and topped that with 4″ of straw with a nod to Ruth Stout.  Here are some pics:

1' deep and about 1' wide - basically dig a trench with a spade and pile it onto your garden bed. As these paths are to be semi permanent I pulled some lines to keep me honest.

Once the trench was dug and emptied, I filled it with chips. I like to use fresh chips with leaves in it if I can - the nitrogen helps to feed the soil ecosystem. Tamp the chips well (walk on them) and mound them slightly as they settle. I aimed to keep them about level with the top of the growing beds. As the trenches are 3/4 full, rake the growing beds flat to get them back to 30" width and then top the trenches off. Figure a cu ft per running foot - these beds are 32' (9.7 m) long so it takes over a cu yard each.

After the growing beds are raked flat, I put down a .5" (13mm) layer of compost which is enough to cover the soil. More is better, but the most important thing is to inoculate the bed with soil bacteria which will munch slowly on the straw all winter and add some humus.

At this point the beds are built and the straw is laid down.  That is all pretty straight forward.  But before I sign off I would like to show some examples of just WHY this is so important:

This was from one of the chipped paths from this summer's garden. These chips were only 4 months old - just LOOK at that fungal growth!

This is also  my answer to any concerns about “locking up nitrogen” by adding this much carbon to the soil.  The fungus is working like crazy to break it down, plus the soil in the growing beds is normal and the nitrogen concerns will only be in the paths or just next to them.  And once the plant roots start exchanging sugars with the path fungus the soil economy will go bonkers to the benefit of your pantry through increased yields.  Just so you understand that this wasn’t an isolated  shot her are some more pics — all from the same row!

Almost 4" thick - the fungal net was already reaching well below the chip layer. Again - this is 4 months or less of growth!

These fungal nets capture nutrients and water reducing leaching and feed worms (see him?) and other soil fauna. Fantastic!

I am an unabashed Soil Geek, but these discoveries had me beside myself, jumping, hollering, and dragging my wife and kids out to see the bounty growing under my paths. Wow.

So there it is, my Pit and Mound gardening method.  Essentially I am taking straw mulch gardening -the tomatoes and other big plants will grow right into this mulch- and taking it up a notch with a healthy dose of soil ecology by fostering fungus, worms and all their buddies in the “permanent” paths.  This also reduces labor by increasing the gardens ability to self irrigate by essentially creating contour swales next to each bed.

Time will tell how much of an impact this will have.  But I do know that some of the best soils on my property are found UNDER my wood chip paths, humus is formed from carbon after all.  Any question about the efficacy of fungus to make soils is erased by going out to a nearby woods and rummaging under the leaves – its amazing.  In addition to the paths, the growing beds now more precisely mimic a natural soil structure – beneath my garden is the sub soil, then a foot of top soil, the the “duff” layer of partially decomposed material in the compost I applied, and topped with raw organic matter in the mulch.  EXACTLY the same strata you will see in a prairie or forest.   Its still a veggie bed, but we’re a helluva lot closer to building more sustaining system as it holds water, suppresses weeds, and builds soil and soil ecosystems.

Be the Change!


34 Responses

  1. Hey – cool post. I was just messing with my paths today to put in some new edging and noticed it was white just like yours and full of worms (mine is about 8 months old). I hadn’t known that fungus was so beneficial, so this is a timely post!

    With a nod to permaculture and no-till practices, I was forming a plan of scraping up all that fungusy half-decomposed path-mulch each Spring and piling it on top of the beds. I’ve got clover green manure growing there over the winter and would smother it that way. I was going to try to plant through it.

    Like you said though I was leery of nitrogen robbing. Do you think that would work? I haven’t been able to slog through a permaculture book yet, so I’m kind of improvising. 🙂

    • The nitrogen robbing should only be an issue if the carbon is mixed INTO the soils. Bacteria can’t move much after all. So if you are just using it as a mulch then I think you will be ok. It would be even better as a mulch on a a perenial garden, under some fruit trees or shrubs for instance. I do not intend to pull the chips up from these paths, but we’ll see what the future brings.

      Glad the post was timely – I recommend Gaia’s Garden as the most accessible permaculture book I’ve read. Very fun and informative.

      • Thanks for that info! For some reason I had the impression that mulch would, like, suck nitrogen up out of the soil or something. -laugh- I would dig trenches like you but I’m gardening *right* at the water level. Literally you dig down one shovelful and the bottom fills with water. So I’m trying to gradually and naturally build raised beds.

      • To summersweet:

        I have a garden bed that gets waterlogged too. Last year I dug a trench, inserted semi rotten branches, and raised the whole bed 6 to 12 inches. It is called hugelkultur: http://www.mplsobserver.com/node/1335.

        So I had no drainage issues, the branches were still there when I tilled just now in the fall, and despite the drought in the US Northeast, did not water my garden once with OK results (only the vines had problems like cukes and watermelon – but I was too busy chopping up a massive downed tree that resulted in 2 cords of firewood).

      • I don’t have my reference books, but the nitrogen robbing effect actually extends 5-9 inches from wood chip mass (not green or cedar chips) because the mycellium distribute it to some extent. Some things are stunted more than others.

  2. We are just in the process of putting in a garden so this post is going to be very useful indeed and it is something we can do without huge expense. I’m not sure how much garden we’ll get this year as we are starting rather late but we should manage some Autumn crops and a few winter things as well.

    I will check out Gaia’s garden too at the library.

    viv in nz

  3. This is how I’ve been gardening for the past two years; it works extremely well. 1 foot paths and 30 inch beds is just about right. If the garden isn’t conveniently accessable, you’ll spend time in other parts of the yard, and weeds will creep in. Now if you run a soaker hose, or better yet two, over the beds, you’ll really be in business. Of course, I’m in a hot climate.

    Bermuda grass, or quack grass in a cool climate, grows across the mulch path, but it is easy to pull the rhizome out of the mulch before it gets established in the soil.

    I actually do think nitrogen “robbing” is an issue. The amount of manure I used should have been excessive, but my plants didn’t reach optimal growth until I supplemented them with bloodmeal. I think that the mycellium digs into the soil for nutrients, and competes with the crop. In 3-4 years, all of the nitrogen stored in the mulch will become available again, in the best possible form.

    One possible disadvantage I’ve noticed is hundreds of slugs. But I call it a possible disadvantage because they seem to prefer fungus to leaves; they only bother seedlings.

  4. Re: quack and mulch

    It has worked incredibly well for me to sheet mulch the entire garden area (including paths). Lay corrugated cardboard over the whole area, overlapping 12″. Cover with straw, if possible, then a full foot of semi-composted horse manure. Ideally, top with 3″ of top soil or garden blend soil.

    At the very least, cardboard and horse manure will do the job: kill all the sod, including quack, and make a nice foundation layer for a garden. If anyone near you keeps horses, you can probably get manure for free. Places with a few horses often have a bucket loader and will happily fill up your truck for free…all you need to do is shovel it out of the truck.

    Plant squash, beans and corn the first year, especially if you’re on 100% manure. Tomatoes will get blossom end rot unless there’s more calciumin the soil. Bone meal can help if you’re in a hurry, but just letting the worms work for a year and blend the under-soil in with the manure works, too.

    Now that I’ve got this bed established and the grass killed, I’m going to try some chip paths, too!

  5. Rob, Love the Blog. I found it a month or so ago and I’m absolutely hooked. I’m very interested in learning to how to grow my soil. Can you recommend a book or two to get me started?

    • Teaming With Microbes is very good and a bit heavier on the science, and Soul of the Soil, by Grace Gershuny is perhaps even better with a bit more applicability for gardeners. Both are accessible enough for someone with only a bit of biology schooling to comprehend, but add depth to that base very quickly.

  6. I read the ramp up and found it pretty impressive. The one name that seems to be nearly hidden is Emilia Hazelip. She learned double digging from Alan Chadwick at Berkley. Had to be about the same time John Jeavons was first starting out. She went to Europe and caught the wave in Permaculture became an instructor and put out some good stuff on Synergistic Gardening. You Tube peices together her one tape (video) and I’ve found a few pages. She was all about One Straw revolution but, had to adapt it to the French Pyrennes. She dug the dirt between the beds sometimes like 20 inches tall. then really got into mulching and planting through the mulch. It’s like Rob is treading along the same path. What I want to see is if her theory worked that there was no need to keep adding compost but keeping everything mulched. I stumbled on to some related sites where this was being used in India and some other places with great success.
    I applaude everyone’s efforts and please keep sharing and updating. It really is inspiring.

  7. […] going to ask my tree removal neighbor for all his wood chips from now on to do this in the  veg garden. I could easily fill up those garden paths with wood chips and leaves. These […]

  8. […] to put in a stand of willow on the north side of our garage, so I started working on that. I love Rob’s description of pit-and-mound gardening – it’s got aspects of hugelkultur, permaculture, and soil-building – and knowing […]

  9. Your article was wonderful and inspirational! I can understand the howling, the jumping and the dragging of wife. 😉

    One thing, however, concerns me. From what I hear, irradiation of anything is really dangerous. It would certainly be an effective weed killer if you could get your hands on a commercial gamma-emitter sterilizer. (joking!)

    Concerning your removal of pesky perennial weeds, I think the word sought was “eradicate” instead of “irradiate”. (second paragraph, next to last sentence)

    Best of luck to you, thanks again for another vision of things going well!

  10. Just found your site and it looks very interesting! I’ll be following it.

  11. hmm, I’m interested to give this a go too. Thanks for the interesting post!

    I’ve been using a thick straw mulch on some of my beds over the last couple of years, inspired by Emilia Hazelip’s you tube vids amongst other sources. Very very nice results – better moisture retention, great crops, very little weeding needed at all and of course that means you hardly need to disturb the soil so any mychorhiza or other soil organisms are relatively undisturbed and can keep that soil nice and healthy. I’ve been using this mainly on my root veg and I’ve had a marked improvement on root size this year for very little work on my part since the mulch went down.

    So I’d planned to put in some new paths and have already bought in some bark chips. I’ve already laid some with an under skirt of thick black sheeting, but will give it a go with just a thick layer of bark for the paths that are left. My only concern is that I’ll get weeds growing through the path, but I guess if I lay the bark deep enough, this will be less of a problem. What’s your experience been with that?

    Cheers again,


    • Nancy – that sounds fantastic! For your paths, it depends on the weeds. Persistent perennial weeds will have the energy reserves to push through the mulched paths, but annual weeds germinating from seed will not be able to do so. With a bit of diligence, non aggressive weeds should be controlled easily. Couch grass or other rhizomatous weeds will be an issue and should be resolved first.

  12. Very cool! It has all of the benefits of hugelkultur, but is useful for crops that are more nitrogen sensitive . Those that are sensitive still need to be 10 inches away or the mycellium will distribute the nitrogen and rob their roots. So maybe make wider rows for those crops.

  13. Hi Rob,
    did you know that Dave Jacke (of Edible Forest Gardens) and Mark Krawczyk are writing a new book on Coppice Agroforestry! Cf.

  14. I just found your site and love it. We are in the process of setting up a no-till, all-natural garden market. We’re double digging all beds (3’x50′) with 24″ paths. So far 5 1/2 beds are done. We have no topsoil so we’re adding dried leaves and cow manure as we dig. We hope to have at least eight beds ready for planting by February 2011. We’re considering thick, heavy cardboard and several inches of mulch in the paths. When the entire field is complete we will have 60 planting beds divided into eight rotational areas, two permanent areas for strawberries and muscadines, and a small apple orchard. Since we are eliminating our carbon footprint and working toward complete sustainability it’ll probably take 4-6 years to get everything complete. Any advice is welcome.

    • I apprenticed at UC Farm & Garden program that Alan Chadwick had started. I remember that planting fava beans was recommended when starting a new garden because its roots were strong enough to easily breakup a hard-pan soil (so easier double digging later); when mature you can harvest the edible variety of fava bean (beware of the non-edible variety!) and compost or till in the abundant green matter from the very tall plant. Plus, its probably set some nitrogen for you too.

  15. Memaw – I’ve tried cardboard under mulch in gardens before. We have a wet climate so it may not be the same for you, but I found the cardboard disintegrated over 1 year and weeds pushed up every Spring. I’ve been pleased so far with using landscape fabric underneath my mulch; or you could just plan on continually redoing your cardboard – it is more eco friendly after all. 🙂

  16. […] over at One Straw has posted about how he is using mulched-filled trenches as paths between his garden beds. This is exactly what I’ve been setting up in my gardens, so I was very excited to discover […]

  17. Hey Rob,
    I looked it up in the academic literature and the zone of nitrogen depletion is about 1 *centimeter* both for horizontally and vertically from even deeply extending mulch or trenches of woodchips, so your method is great!

    I haven’t looked up what happens if vegetable plant roots actually partially extend into the woodchips. I could see the plant roots transporting N from soil to wood chip trench, but maybe not.

    Very cool!

    • Great! My estimates were in the 1″ range at most – things just don’t move that far in the soil since bacteria have virtually no locomotion and they would be the ones “locking” the nitrogen. My research has also led me to believe that the roots only exude sugars into the rhizosphere and then only to promote bacterial growth when needed; I suspect any nitrogen lost to the wood chip zone would be in root hair die off. Also, the roots would only grow “towards” favorable conditions. I can certainly see them growing into the mulch for water – in fact I know plants trees do this in old growth forests where rotting deadfall trees are a large water source. What is also likely is that immediately outside the “locked nitrogen zone” will be a very fertile region where the bacteria are dying and its still moist from the water in the mulch. THIS will be a bonanza for the roots of the annuals for sure. Again, its the edges that are the most exciting!

      Thanks for “digging” into this!

      • I think mycelia are able to transport nitrogen farther, but they might not extend very far into bacteria-dominated “turf”.

  18. hi rob – OS-BTC has been an inspiring place to learn from.
    saw you drop into my blog with encouraging words. any thanks for that and this, of course.
    sitting in a remote part of rural india and connecting and learning with friends like you is breath-taking.


    • Sriram – I am so glad that you are finding things that are helpful. The pictures of you gardens looked fantastic – great rich soil that should be incredibly fruitful for you in the coming seasons. Hopefully the chipped paths will help with water management as they do here and in the warmer temps the soil life should be incredibly active – you may need to replenish the material faster than we do here in the States. That would be a great thing as you will be making humus twice as fast as we do.

      Also look into adding charcoal (bio-char) to the beds/paths if you feel you are having nutrient leaching due to heavy rains – not sure how bad the monsoons hit you in your local, but that could be a limiting factor as well.

  19. […] Science, and the learnings from that project were profound enough that they inspired me to revamp the way I plant my gardens,  created and taught several workshops on Introductory Soil Science and posted enough about […]

  20. […] plenty of compost and vermicompost along with some green manures and deep mulching before fall and laying the ground work for rich soil ecosystems.  Still working through the planting layouts for the year, and need to […]

  21. […] me to reconsider how I plant. The second is reading an article by another blogger. In his post on Pit and Mound Gardening, Onestraw talks about creating mulched trenches in his paths to improve drainage and water […]

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