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Preparing clay soil for planting fruit trees?

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  • Preparing clay soil for planting fruit trees?

    Please help! I'm in Auckland, NZ and I'm planning to turn some lawn into a productive food forest of sorts and would like to plant dwarf/semi-dwarf fruit trees as part of that. The space is roughly 15m x 8-9m (not quite square). It already has a fully grown grapefruit tree to one side of it (the drip-line is just on the edge of the space I'd like to cultivate). We get plenty of grapefruit from it, though it's starting to look a little yellow on one side. The soil is very heavy clay (soggy/marshy in winter, dry/cracked in summer) and has been covered in grass (including kikukyu) for a long, long time.

    I can wait until next winter to plant the fruit trees, so that gives me almost a year to prepare the soil. I'm only renting my place, so I don't want to do anything too majorly invasive/costly. I was thinking about using chickens to clear & fertilise and then some kind of sheet mulch/cover crop/clay breaking soil improver. It will have to look relatively neat to appease my more conservative neighbours (the land has 6 flats on it and is communally owned). What would be your permies' advice?

    Is it possible to plant fruit trees using a 'no-dig' approach? (Other than in containers, I mean!)
    Will a deep sheet mulch left for almost a year help to improve the soil?
    What about using alfalfa/daikon radishes/potatoes to break up the clay? Is it possible to do this amongst a sheet mulch?
    Would it still be a good idea to dig in the broken down sheet mulch before planting the trees next winter?

    Thanks everyone!

  • #2
    Are the chickens going to stay on in the long term or would you bring them in then retire them? If they are a short term solution then I would think it isn't worth the effort involved.

    I'd sheet mulch it really (really!) thickly, and use manures as part of that. Leave it settle in for 6 weeks or so and then plant potatoes - or kumera would be culturally appropriate for NZ! Dropping seeds for daikon or green manure crops into the sheet mulch too early are probably not going to work, but a few months down the track once it has composted down you could then do a green manure crop, and that would get dug in, and depending on how much time you have left before you want to plant your trees you could repeat it. You don't need to (and shouldn't) try and dig the whole sheet mulch layer in. That's what worms are for.

    Also think about the support species you are going to use, and you could start putting them in ahead of the fruit trees.

    The aim is to build up the soil before the trees are planted. Done correctly you should end up with a nice thick layer of friable soil that is easy to dig in for planting.

    Don't forget to think about how you are going to trap and use water in the system, and where the sun goes.


    • #3
      Have you seen Kay Baxter's book on orchards? She covers this situation exactly, and she's even in the same climate! The library should have it.


      • #4
        Dear Crystal Lil,

        If your clay soil is water logged in winter and cracking in summer,,,, then it says 2 things to me,,,

        1st . the soils calcium - magnesium ratio is out of wack ,,, and if you work to get it in balance the water and nutrient holding capacity will improve over time and the cracking will not be so severe over a few seasons. this explains it the albrecht method :-

        2nd it could be worse,,,and its not that hard to fix.

        Other soulutions are,

        1. get support trees in now ,,,, tagasaste planted wholly to be sacrificial mulch providers over time,,, maybe keeping one of them on the most cold windy side perhaps.

        2. why wait until next winter to plant your dwarf fruit trees,,,if its a small little garden of 15 m square, it shouldn't break anyone to give a bucket of water in late summer once per fortnight say,,,, if you follow good garden practice with deep mulching,,,and planting the trees into deep holes that are filled with good mulchy soil down low,,,there should not be a problem ,,,,,, only if planting broardacre lots that require irrigation should folk really be worried about time of planting,,,, its only a handful of trees,,? Auckland summers are mild and I dont think you should be too worried or go into great delays to prepare the soil? planting the trees will prepeare the soil for you via photosynthesis action,,,added with your mulching will all help down the line.

        yes it is possible to plant trees in a no dig situation,,,

        planting comfrey / vetiver grass will provide a barrier for your kikuyu ,,,,

        add a cup of molasses to a bucket of boiling water,,,stir it,,, wait for it to cool,,,and water your plants with that as they go in,,,,,this will encourage fungi activity at the root ball and greatly help your soil conditioning from pasture/grass bacteria dominated to a forest/fungi friendly environment .

        I think folk tend to over think things about ground preparation,,,,whilst good design and placement is the name of the game,,, getting the trees in aids in the process itself. comfrey , salad greens, clovers and herbs around the base of the trees will be your friends,,,why wait.

        happy planting,


        • #5
          Crystal, I have a fruit orchard in clay, really tough clay, and it took almost two years of mowing greens (weeds, lawns, etc.) and thick mulch before the soil around the trees got enough organic matter in it. It will absorb it, even weekly, so keep replacing it. The key is never let the clay be exposed to the sun or the pounding rain, so mulch a minimum of the depth of your hand, or more, is crucial. It needs to be this thick so the mulch will be damp at the soil level and will work like a mini compost pile. Keep the mulch a good finger's length away from the trunk so it won't rot.

          Don't put manure or fertilizer in the planting hole because the roots will get lazy and start to circle, being unwilling to leave the overly-amended area. You can make compost tea in buckets or a garbage can for three days, then soak the bottom of the planting hole so it goes down below it, then the roots will go down below it, too.

          I love clay because it's full of minerals, which add great flavor to vegetables and fruits, and it holds water, so you don't have to water as much. Although when starting fruit trees, they do need more water, sometimes twice a week if it doesn't rain enoiugh. Water slowly but deeply, drippers at the dripline of the branches so it goes very deep and the roots have to go down to get it. Don't use sprinklers, that will water too shallowly. If the clay dries out, simply water it deeply, cover it with a tarp or a board, let it sit for a few hours, and it will be easy to put a shovel into. Think of it as cooking with wheat flour instead of white flour, it takes longer for it to absorb moisture.

          I have added granite sand, which is a 10-year source of phosphorus, and I've done raised beds with almost %50 granite sand for carrots, which I've never been able to do without it. Keeping the soil moist will bring in the worms, and the mulch will feed them. But they will go too deep if you don't keep it damp enough.

          I think it's more important to keep sheet mulching on top of the soil. The worms and beetles will take it down into the soil for you. Just don't let the clay show ever again.

          And you probably know, when planting always plant the graft side of the tree, where there's a knot at the rootstock level, to the north in the southern hemisphere, the south in the northern hemisphere so the sun is on it, and it won't get algae or moss on it. Keep it a good two finger-lengths above the soil.
          Last edited by sweetpea; 13-09-2011, 04:45 AM.
          "Life flows on within you and without you"...George Harrison
          Coastal California, USA, Mediterranean climate - no summer rain, a little frost mid-winter


          • #6
            Thank you so much for all your helpful replies.

            eco4560 - I am planning on keeping chickens anyway for eggs, compost and generally to have nice pets. I thought they would do a good job of clearing all the weeds and kikuyu, which has always found a way to come up through any sheet mulches I've done in the past.

            pebble - I have borrowed Kay Baxter's book a couple of times and actually have it out at the moment! I had a look through her suggestions and wasn't sure whether sheet mulching or rototilling would be best in my situation. The main cause of my uncertainty is whether I need to do anything drastic to improve the drainage - but I'm probably over-thinking it a bit. I should just get on and do it!

            barefootrim - thank you for reassuring me that it's not too late to plant trees now. And for the info on magnesium/calcium. In fact, thanks for all your helpful info!

            sweetpea - it's so good to hear that someone else has had success under somewhat similar circumstances. Your detailed instructions are really helpful! When you've added your granite sand, do you just layer it on the top of your mulch, put it under the mulch or dig it into the ground? I added sand into my vegetable beds when I dug them over to get them going. I'm not planning on digging them any more - just using lots of mulch.

            So - am I right in thinking that to plant the trees, I should dig a hole, mix the soil I take out with compost, soak hole with compost tea or similar, put tree in hole & back fill with soil/compost mixture? Then mulch like the devil and also plant comfrey & other herbal ley stuff around about?

            Thanks again!


            • #7
              Depending on how compact your clay is, you may want to double dig. The area should also be as root free as possible. I did a massive area this last year to establish a main garden at our home. Without double digging it would have been impossible to grow the plants we did this year. I've read that double digging isn't proven to help with woody plants, but I'm definitely sure that breaking up clay that was previously hard as a rock (meaning you couldn't put a shovel into it all the way) will help anything grow.

              Great thread though, I want to plant some fruit trees in the next couple of years and we have clay too so its nice to see responses now.
              Pre-June 2012 A Victory Garden documents our typical American suburban lawn to a food forest based upon the permaculture principles.
              Post-June 2012 60° N Permaculture follows my permaculture explorations and integration story in Finland.


              • #8
                When you have dug your hole fill it with water and observe the drainage .If it does not drain completely in one hour you will need to build it up.
                the end of suffering comes from the living of joy!


                • #9
                  Gypsum is great for breaking up clay. You do need a lot but it is cheap.
                  Dolomite may also help + all suggestions already made esp organic matter, mulch and worm food.
                  "You can fix all the world's problems in a garden. .Most people don't know that"
                  Music can solve all the world's problems. Not many people know that- MA 2005
                  "Politicians will never solve 'The Problem' because they don't realise that they are the problem" R Parsons 2001


                  • #10

                    I wouldn't recommend amending the soil that goes around the roots with compost. You can Google this, but I think there are a lot of findings to back this up. The roots won't go beyond this newly enriched stuff and they will circle, becoming rootbound. If you wanted to add rock powders, granite sand to it, that would work. But save your compost for the top, under the mulch. Then watering sends down even more compost tea and the roots will go search for it. Always amend out to the drip line so the roots will have to reach out.

                    I don't till anymore. My rototiller broke and it was either get it fixed or get tires for the car, and guess what won? But in the meantime I started doing 1/3 meter/1 foot deep-mulch beds. I'd always mulched, but never this deep, and it is one of the best things I have ever done.

                    I put the sand down first on damp soil, then start layering mowed weeds, and walk on them to compress them. Then plant directly into this mulch. The roots of transplants seem willing to keep searching for soil and water when in mulch, but if they find dry soil (some raised beds use layers of soil and leaves/grass) they stop looking and the plant fails. It's a lot easier not to have to drag heavy clay around, so I don't anymore.

                    So now my soil is always damp, there are worms up in the mulch, squashes, pumpkins are sitting on clean, dry mulch. And I only have to move the mowed stuff once, at least the majority of it, rather than compost it all, then move it again.

                    I put stubborn things, like crushed egg shells in the paths, and wood ash, and it disappears. I think the walking on it helps, but even the soil under the trees, where I don't walk, the soil critters break it down and take it down into the soil. I guess I would say, there's no such thing as too much mulch
                    Last edited by sweetpea; 14-09-2011, 04:35 AM.
                    "Life flows on within you and without you"...George Harrison
                    Coastal California, USA, Mediterranean climate - no summer rain, a little frost mid-winter


                    • #11
                      I was going to ask more about your mulching, sweetpea. I've read that too mulch mulch can create anaerobic conditions, but you advocate at least a hands depth. The most I've laid down ever, and this is just this year, is about 5". Of course, climate conditions will dictate how much mulch you can ultimately use.

                      So, my question is, how much mulch have you been using and for how long? You are in a warm climate so I assume i breaks down rapidly? Anyway, more info on that would be great!
                      Pre-June 2012 A Victory Garden documents our typical American suburban lawn to a food forest based upon the permaculture principles.
                      Post-June 2012 60° N Permaculture follows my permaculture explorations and integration story in Finland.


                      • #12
                        Finchj, I know they are always talking about anaerobic conditions are not desirable for compost, I have yet to have bad compost or problematic mulch. Those piles are not air tight. There is enough air in there for fungi and bacteria to form, it's easy to see it within just a couple days. It's not like the amount of air we need.

                        I make compost by layering whatever I've got and putting pressure on it with boards, blocks, heavy bags of potting soil over a tarp and squishing it. It breaks down really fast. A friend of mine researched about the anaerobic compost pile conditions and found that the bacteria and fungi can actually function under either condition, too wet or dry, they actually morph back and forth. We laughed that they "swing both ways". And I mentioned that if you look at the edge of a pond where the water is saturated in the soil, yet retreating in the summer there is always some of the greenest vegetation at the water's edge. Nothing dies because it's anaerobic there, so that's an example of how soil fungi and bacteria adjust to moisture levels.

                        Even in the winter when it does rain, I have garlic, onions, lettuce, brassicas going all the time, and the clay soil is always friable under that mulch. The rain does not pound the clay down, which might make the clay anaerobic, you know how it gets when clay is saturated, it is impossible to dig into when it's too wet as well. But the thickly mulched beds avoid all that.

                        These are Permaculture beds, that's where I got the idea to go to these deeper beds.

                        It is dry/arid where I am in the summer so I control the moisture, but this spring we had unexpected heavy rains right at planting time, and if I hadn't had those mulched beds in place I would have had to wait 2-3 more weeks for the clay to dry out so I could plant. That would have been a nightmare, because I sell produce during the summer. Everyone is expecting everything ASAP!

                        I pull the mulch aside, throw in a handful of compost or chicken manure, put my transplant down, and tuck it back in with mulch, water it a little, then rely on the drippers after that. I am more concerned about air pockets that the roots might find, because then they faint. Every week I use my foot to press gently around the plant to make sure there are no air pockets.

                        I have mice and voles that run around at the soil level, but so far they are not causing any problems with the plants. Before I used these beds the plants died a lot because the little tunnels they made dried the clay out, it cracked open and the roots dried out. I couldn't even begin to water enough.

                        I think there's a lot less stress on the plants, the moisture is more consistent even if I am not around to water one day, and I know the soil improvement is going on all the time.
                        "Life flows on within you and without you"...George Harrison
                        Coastal California, USA, Mediterranean climate - no summer rain, a little frost mid-winter


                        • #13
                          Thanks for the reply. I think we need to have more mulch! We were sowing some lettuce, spinach, cilantro, and sunflowers (crossing my fingers they will flower before frost, just as an experiment) this evening and the soil was still moist, but the entire mulch layer was bone dry. I had just watered deeply two evenings ago. In the areas with more mulch some of it was still moist- which I think is a good thing. So I'll pile on some leaves this fall. Going to get as much from our neighbors as possible this year. If I do, by whatever happenstance, begin to have problems I can always remove some mulch and put it to use somewhere else.

                          Thank you again
                          Pre-June 2012 A Victory Garden documents our typical American suburban lawn to a food forest based upon the permaculture principles.
                          Post-June 2012 60° N Permaculture follows my permaculture explorations and integration story in Finland.


                          • #14
                            So anyway, respectfully back to Crystal lil,

                            Its not so much you want to put the same soil back in the planting hole as you took out,,, at the bottom of the in-going plant,,, in a deep clay area (or new sub-division where all top soil is gone perhaps) it is best you put a good neutral compost at the bottom of the ingoing plant ----- by neutral I mean a compost soil that wont burn or has gone through its heat process,,,or has been well worked by microbes---- this will encourage the roots of the potted plant to come down into the compost,,,,,, if all the composty soil is on top you'll have roots reaching up for it.

                            In my 5 years of living in heavy clay areas,,, I planted my fruit trees 3/4 potted rootball in the ground,,, 1/4 of the potted root ball sticking out of the ground and in stead of mulching like the devil,,,, I mulched like an angel would,,,,very heavily,,heaps of humus,,,heaps of straw- mouldy hay, heaps of grass clips. Go to town.

                            If you read Dr Albrecht's papers,,,and go into cation exchange capacity and all that jazz,,,you find its mentioned a lot,,,, briefly (in a sentance) cation exchange is fertility on cation/anion polarity,,,and is reached by the minerals of clay mixing with humus to give the exchange..... Since you have heaps of clay (ie minerals) present you have to ask yourself as a gardener do you have the humus ( sitting on top of the soil) to mix with the clay (via worms and little critters) to give good cation exchange. mulch like an angel,,,tehe.

                            all the best

                            In a no dig garden,,,you cut a hole in the cardboard for your fruit trees


                            • #15
                              So great to get all these replies & comments. I'm going to have to get a bit creative about where I gather mulch materials from, I think. There is a lot of lawn on our property (again, communal, shared betweemn 6 flats) but there is a contractor mowing man who never uses a catcher and mows about every 3 weeks, so there never seems to be an abundance of lawn clippings to collect. He also sprays the edges with roundup or something, which seems to be a common practice in these parts to keep it 'tidy' (I suppose to stop the kikuyu spreading). Personally, I think it looks bloody awful and it messes with the soil on the edges of the lawn. However....

                              I'm currently growing veggies on about a 10m2 site and composting everything that I can from that. I'm starting to produce enough to put back on this small patch, but there's not much left over. I live in the city, so any straw or hay bales have to be bought and transported (which I have done before in the back of my corona liftback - but you can only fit a couple in there!) According to 'Gaia's Garden' "bomb proof sheet mulch" instructions, I would need around 10 bales of hay/straw to sheet mulch a 20m2 area (I think?). I started a sheet mulch garden off a few years back and put out a request on freecycle asking for materials. That was relatively successful but I had to hire a flat-back truck to go around and pick them all up. I ended up driving quite a long way to get some of the stuff too.

                              This time, I'd like to do it much more locally and without hiring transport, if possible... time to put my thinking cap on! Has anyone got any clever suggestions? One thing there is in abundance around here is used coffee grounds (lots of cafes). I can probably gather grass clippings too and maybe a little seaweed (if I'm lucky...there never seems to be that much on the local beach). I'm trying to find a local source of sawdust/sood shavings for my intended chickens. Lots of the trees around here are evergreens and it's not the right season for a lot of leaf drop from the deciduous ones. Time for a walk around the neighbourhood to suss things out, I think!

                              One other question I had was around pruning. I've read about lopping trees off at knee height after planting so that you get trees of a managable size for small spaces and easy to reach for picking. There are some heritage fruit trees I'd like to buy but none of them come on dwarfing rootstock (because they don't do well on clay soil, I think!). Rootstocks are Northern Spy or 793 for apples, quince or pyrus for pears, and peach for peaches. Will it work if I plant and then lop off the top at knee height? Sounds so brutal!!! (Maybe I should start a new thread about pruning???)

                              Thanks again, kind people. I learn so much from all of you.