Which size mesh for sifting stones out of rocky soil dug 2 feet deep for biointensive garden

Hi everyone, this is my first post. I am new to gardening.

I have been reading the book "How to grow more vegetables by John Jeavons", and I have started digging what will be a 33 feet long 3 feet wide portion of the backyard. (3 feet wide is all I was allowed to use, so it will have to do.)

Unfortunately there are very big rocks which have bent the tines of my spading fork during attempting to double dig. The spading fork is completely destroyed. I couldn't even loosen the soil the first foot down. So I have started to do a one time dig to remove all the soil a full 2 feet down in order to get all the huge rocks out so it will be easy in the future to do double digs, and it will also be easy on a new spading fork. I have finished digging 2 feet down in a 3 feet by 3 feet section and I have 10 more of those to go.

The problem I am having is that I want to sift the soil as I put it back, and I have tried to find some info on the internet about what size mesh to use, but most of the info I find is for just the topsoil or compost. I also can't find anything in the book I mentioned about sifting rocks from soil, let alone 2 feet down. The book only mentions sifting compost. I am running out of time and I need some help to understand what size mesh to use to sift this soil.

I have been looking at 1/2 inch and 1/4 inch hardware cloth. At first I thought I should take out all the stones. But now after reading a bit, I see that stones can be benificial to the soil structure, at least smaller stones to allow the soil not to compact too easily and to have better drainage.

I don't know what size stones I would need to leave in the soil to have a good soil structure. Before I found out that I shouldn't be taking out all the stones I was thinking that 1/2 inch mesh looked too big to me, and I was going to go with 1/4 inch, but now I don't know what would be best for the soil structure. I am only begining to learn about soil structure and I don't want to do anything to damage that 2 feet down.

I would very much appreciate if someone could explain what size mesh I should use to sift the soil before filling the hole to keep only the stones that are necessary for the best soil sturcture and to remove everything else, and also considering I have dug out all the soil 2 feet down if that makes any difference (should it all be the same soil structure the full 2 feet down?). It is a lot of work to dig 2 feet down to remove all those big rocks and I want get the correct amount of sifting done so I feel very good about all the work I will be doing.

Long story short,

I utilize 1/2 inch hardware cloth and I think it works well.

Big stones get added to an ever-expanding rock wall while the smaller stones get used as permanent mulch around my homes foundation.

The rocks that get through the mesh have not caused me any issues from what I can tell.

I hope this helps!

If I may ask, what kind of soil do you have besides the rock?

Welcome to Permies!

I too used a 1/2 mesh for some of my garden beds. I did not use that size for any particular reason... simply that I had it handy.

I never went as deep as you are though. I just did the top 6-8" so it was easier to transplant. Here in Maine, I'm pretty sure we grow rocks, so I didn't go any deeper. I just worked on my soil health, and it seems to have helped the roots get to where they need to go at that depth.

We have two sizes of mesh for general gardening.  Half inch is used most often and quarter inch is good for the very top inch or less, but only when starting small seeds.  Any rocks bigger than about an inch can be picked out by hand when digging.

If memory serves, this is the half inch siv.



It's actually a bit large a frame for me as soil is heavy.  If I had my druthers, a frame about half that size would be more efficient.   But it's four generations in our family (with repairs),  so that's the size it is.

Edit to add- most of the time when building new gardens, I don't siv unless I'm on glacial till (excessive drainage) or have really tiny seeds like carrots or smaller that have trouble with obstruction.  Hand picking the soil is worlds easier and most plants don't care about rocks upto four inches.  

Also, no matter how well sifted, rocks will reappear each winter.  It's one of those mysteries like toast always landing jam side down.

That sounds like a ton of work. I'd bust it up a little bit however -- spade or broadfork (and I'd only pull out the worst of the rocks) and then just sift a couple inches of compost on top for planting seeds into.1/2" is fine.

Thank you Timothy, that helps! Are you doing the Biointesive method as well?

I would also like to know more details if anyone has anything to add such as if it wouldn't be as good to use a 1/4 inch mesh compared to the 1/2 inch mesh. Or maybe someone wants to just post a link to something that I can read which may enlighten me.

To answer your question I am just learning, so I don't understand what soil should be like other than how it should be not too sandy and not too clay like. But it looks good and feels like a good texture in the hand and is a nice dark color. It does seem to drain water slowly from when I watered it to prepare for a double dig, but that could be the big rocks. About a foot and a half deep it gets very clay like and a light brown color and very compacted, but it still breaks up into soil after digging it out. Other than the large amount of very big rocks and medium rocks, there is just a normal amount of smaller rocks. My uncle says that when my grandfather built the house, they dumped a lot of big rocks in the back yard and covered it with soil.

The backyard just had the grass replaced and those people put some better soil in the garden section, than what they put under the grass, but probably only 6 inches deep. It still looks just as good for that foot and a half.

Quarter inch is a lot of labour (about five times the labour of using a half inch mesh) for very little benifit and, depending on the soil you are working with, a risk of compaction and reducing drainage.

Quarter inch is great for the light dusting on top of fragile and neigh invisible seeds.  

What is your subsoil like?  If it's not sand and or gravel, perhaps keeping the rocks would work to your advantage.   Also, do you get rain at least once a month in the growing season? if it's that often, draining might be useful.

My own personal expierence in the climate and soil types I've gardened on is that sifting is seldom useful.  But sometimes it is useful.  Always it's a massive amount of labour.  In the video, I sived as I neded to reduce drainage as we have 5 to 7 months of zero rainfall and this garden is on top of about 400 feet of glacial tilth which is some of the best drainage in the world.

But you won't know what works for your climate and soil until you try.  So how about dividing your garden into three.  First third is hand picking the stones. Second is one or half inch siv.  Third is quarter inch.  Then you can observe what works and have a control group to compare it against.

Note, if you ever move, it's good to repeat the experiment as every soil needs something different.

r ranson, thank you! It helps to have a general rock size to follow. I also agree with you that I wouldn't be sifting the soil either, but since I already dug it out and there is so much of it, I want to sift to make sure I get out the bigger rocks that I missed and I just thought why not sift it with the correct size mesh while I'm at it. But I was also thinking the further down the less it is useful. Rocks reappear? interesting. I assume not the huge ones though.

Your next post has a good amount of information that I was looking for. Thank you so much! Yes I get a good amount of rain. I am in Montreal Quebec in Canada. Drainage looks like it will be important which is another reason to get all those big rocks out. There is just so much soil I dug out which I have to go through to check for rocks that I am going to make a 2 foot by 3 foot frame for what I now have decided will be a 1/2 inch mesh to sift everything since I can't imaging going through it by hand faster than sifting it. I guess I can just dump some smaller rocks back into the soil if it looks like it is needed after finding the bigger rocks with the siv.

Christopher, yes it is a lot of work, but the huge rocks go all the way down and they are everywhere, there isn't one spot I can get through with a spading fork after the first 8-10 inches. It's just a bunch of huge and medium rocks filled with soil. I can't manage to do a double dig at all unless I do this. If I was just doing a normal one foot dig I would be able to do as you suggest. As I said in my last post, the back yard was filled with huge rocks when the house was built (1962) and then covered with soil. Thanks for the 1/2 inch confirmation.

E Dowe wrote:I would also like to know more details if anyone has anything to add such as if it wouldn't be as good to use a 1/4 inch mesh compared to the 1/2 inch mesh.

The guy we bought our property from left us a wood frame with 1/4 inch mesh.  He had dug a area for the house foundation and might have used it for that.

While I don't know what he used it for that would work for rocks that are 1/2 inch to 1/4 inch which seems good to me.

It all depends on what kind of rocks you want to shift out.

We have a lot of rocks that are baseball size that we simple pick up and put in the wheel barrel.

We also have lots of two ton rocks that we pick up with the tractor.

My dad had built a sieve using 1/2" hardware cloth that I still use.  It is literally an antique; I'm almost 65 and he probably built it some 30 years before I was born!  The only thing I use it for is my compost.  I set it atop my wheelbarrow and shovel out the compost from the bottom.  Anything that doesn't fit through goes back on top of the pile.  What comes through the screening is absolutely lovely to use.  

As far as your situation, I would say that you don't really need to go any deeper than you already have.  Most annuals don't have very deep roots, and perennials will find their way around what's there.  My advice would be to build up.  Mulch up leaves in the fall and add.  Add grass clippings.  Keep augmenting the soil that's there with available plant material. Mulch with wood chips.  If you think about it, when you harvest food from a garden, you're taking out a great deal of mass.  That needs to be replaced.  My front garden used to be much lower.  By regularly adding plant matter, the level has risen a bit while the quality has improved dramatically.  Before it was just sand; now it's deep, dark soil.  The one exception to this is that you will want to remove any dropped fruit so as to not carry over diseases, unwanted fungus or insect larvae.

The latest research says to not till.  There is a lot of life in good soil, and by tilling it, you're disrupting the micro ecosystem that helps plants thrive. Good old cardboard boxes without labels and tape will also help by keeping in moisture and acting as a weed barrier. (I've read that you want to soak it so that water will be able to penetrate it.)  When you till, you're bringing up fresh weed seeds.  rather than pulling up plants in the fall, some even suggest to leave the roots of plants in the soil to break down, in other words, you'd cut them off at soil level.

In permaculture, you'll hear the term, "Chop and drop" which basically means that you cut down plants at soil level and leave the material right there.  When I harvest rhubarb, for example, I cut off the leaf part and lay it down where I think extra mulch would be helpful. It eventually will break down and feed the soil, but meanwhile it's acting like a mulch and preventing unwanted plants from growing there.

The best advice I can offer is to not have exposed soil.  Some sort of groundcover plant and planting in layers will help with this.  I use strawberries out front, but I also have sweet woodruff among many other plants.  Wood chips are a wonder and can be gotten from local arborists who are eager to get rid of them (usually for free.) They are great for pathways or for putting around plants.  Another thing to be aware of is to edge your garden.  You can spade out and down about four inches or so, so that nothing will cross into your garden bed like crabgrass.  Personally, I edge most of my beds with hosta because it's well-behaved, densely rooted so little can get by, and it's once and done.  It also makes it easy to mow any lawn.  

I wrote more than I thought I would.  I hope you find it helpful.  You can research any of the afore-mentioned ideas: no-till, chop and drop, permaculture groundcovers, etc.  Good luck on your new adventure!  I've included a picture of the front garden just as I started it.  You'll see the hosta and the mulch.  I'll try to add another picture of it more recently after.

Here are a few more pictures showing the idea of edging.  The driveway and sidewalk are exceptional for this!  I interplanted many flowering plants to entice insect life, and because so many people walk their dogs along here, I needed it to be pretty.  It is on a state highway, so I wanted them to also help act as a filter and if dogs pee on the flowers, that's fine; they act as a buffer from the Regent serviceberries and asparagus and strawberries (which have really filled in and I no longer need to apply mulch or woodchips. The garden is south-facing, so when I talked about layers, I planted trees on the northern edges and have shrubs in front and around them.

Thank you Barbara, you've given me a lot to think about. I appreciate that very much. The longer the post the better. Thank you for all that detail.

Unfortunately tilling is a big part of the biointensive method that I am learning about. But you have made me interested to learn other methods. I will now be researching permaculture in the following years after I have attempted the Biointensive method for at least a couple of years. I'm curious what all the differences are. I'm interested in a self sustaining organic garden mostly, but the biointensive method is said to create more of a yeild which is the reason for the double digging or really digging the first foot and loosening the second foot.

I finally got the wood and 1/2 inch mesh and will be assembling the sifter by the weekend.

Thank you everybody once again!

Although if anyone else has anything to add, I will be checking back here.

You are most welcome.  It's funny how, no matter what it's called, all of the various methods of gardening are agreeing on so much.  No. 1 is really about building up the soil and not having neat rows of single crops or leaving soil uncovered.  Diversity  is key.  I was attracted to permaculture because it's almost "once and done" gardening.  Trees and shrubs and perennials make up the garden.  The only part I was leery about was that most would be fruit and I was worried about so much sugar, but I guess that is not a worry.  I've been feasting on asparagus for about a week or two and today I had a haul of wine cap mushrooms...much more to come! Once it starts, I'll be pulling out buckets of fruit through December...if the medlars and persimmons produce this year. Tomorrow, I'll have to go out and grab some rhubarb for the freezer.  Maybe I'll even make another batch of wine with it. The idea is to plant in layers, from ground covers up to trees, understory and overstory if so desired. Anyway, I was hoping that you wouldn't find the above posts 'bossy' but instead instructive, so I appreciated your note!

It sounds like you might be renting and that your landlord didn't give you too much land to work with...maybe he was afraid you'd lose interest and the garden would end up as a pile of weeds; prove him wrong!  If you are renting, you wouldn't want to invest in the cost of trees, let alone the time it takes for them to come to fruition.  I wish you all the best on your new-found passion!