The worst clay soil on earth

St. Louis, MO(Zone 5b)

I have the worst clay soil on this planet. I was digging down deep in a area to ammend the soil when I saw just how bad it is. It's perfect for a pottery class. When I got down about 8 inches, the color went from medium brown to a lighter tan! I was disgusted.

I am planning to start digging the stuff up in my raised beds, tilling and ammending it with humus, compost and perlite. Does this sound like overkill? Is compost and humus too much?



Precipice Valley, BC(Zone 2a)

No you don't, Maureen--*I* have the worst clay soil!

When we were planning our garden, on our new site, DH said it would be easier to build up and fill raised beds with 30" of new stuff than to dig the beds! But we did it just with the vegetable beds; all my flower beds are CLAY CLAY CLAY.

I now bribe "someone" to dig down 2' and I fill the holes with a mixture of clay and other things. Clay has good nutrients--it just doesn't allow the roots to breathe or the water to drain away.

So, humus, compost and perlite aren't overkill!!!!! Find some sand and add it too. Add leaves. Non-sprayed grass cuttings. Dig up your neighbour's garden in the dead of night. Sneak into your nearby park. Go to the beach.

I think dolomite lime helps break down the clay, also.

Where do you live?

Cary, NC(Zone 7a)

Hello Maureen,

I understand your plight, I live in central NC and that is all there is once you get beyond the first 2 inches of topsoil. I have done the double dig routine and then added the usual compost, peat moss etc. mix but started to get to tired to garden with the upkeep.

Anyhow, if it is that horrible, it may be worthwhile for you to consider raised beds, which is what I did for a vegetable garden. Then I modified it to have something like a "lasagna garden bed."

This method has been great and very successful for the last five years, bumper crops of tomatoes, lettuce, beets, peas, etc. You name it, it's growing.....

East Bethel, MN(Zone 4a)

I have clay, rocks, and tree roots. I recommend building up as well!

Josephine, Arlington, TX(Zone 8a)

Hello MLMO1, I know what you mean about bad soil. There are many ways to solve a problem, but if you want a permanent solution, sometimes the hard way is the best.

St. Louis, MO(Zone 5b)

LOL Chilko,

Those sound like things I've thought of, except my neighbors yards are probably as bad as mine! ;)

I live in St. Louis County Missouri, zone 5b. I knew we had clay but I didn't know just how bad it was until I started digging.

About the nutrients in clay--does that include the light tan colored soil I ran into? I thought light colored soil was bad, but I don't know much.


St. Louis, MO(Zone 5b)

Hi Yankee,

Although the area I dug in was not raised, I do have raised beds, I just wonder if they are raised enough. The guys who did it did not dig down below the surface, just added compost and top soil on top. (I was very unsatisfied with their work, but that's another story.)

This has me wondering if I need to double dig anyway. How deep does the raised bed needs to be?



St. Louis, MO(Zone 5b)


You describe my soil perfectly on your site where it says "...a sticky gook when wet and like a brick when dry."

This sounds like what I may have to do with my existing raised beds.

Here's a silly question, where do you put all the dirt when you dig it out?



BTW--beautiful site, and great choice of music!

Josephine, Arlington, TX(Zone 8a)

Hello Maureen, If you catch your soil at the right ammount of moisture, not too dry, not too wet,
you can break it up as you take it out, one thin slice at a time and lay it to the side of the bed.

The trick is not to cut too large of a clump, but rather thin slices, it breaks up better that way.

You will use that soil to layer with your ammendments and when you finish you will have a lovely raised bed.

Thank you for the compliments about our site, my husband built it and I took the pictures and did the research.

SE GA, GA(Zone 8a)

Be careful with clay soil.

Adding sand will simply create bigger issues unless....that is the important word...unless you add enough sand so that sand is 45% or more of the total volume. Less than that percentage and you will end up with something akin to brick which is no less impossible to garden with.

I would recommend that you go with raised beds because you can eliminate the work of trying to amend the soil and avoid the problems that come with inadequate amounts of sand.

The other advantage of raised beds versus amending the soil is being able to avoid drainage issues. Raised beds will drain out of the bottom but digging out an area of soil and amending it will basically create a bath tub effect.

Tons and tons (not literally) of compost and any other organic matter you can get will help over time but you will always have clay soil.

Good Gardening!


St. Louis, MO(Zone 5b)

>>Raised beds will drain out of the bottom but digging out an area of soil and amending it will basically create a bath tub effect.

I never thought about that but it makes sense. I'm going to try and ammend some of the soil under my raised beds and try to build my raised beds up higher.



Windsor, Ontario, ON(Zone 6b)

I just dug in a few flowers that I brought from my old house, and we're all clay here, too, and everything that's dry is brick. I asked my husband to get some nice soil to mix into the raised beds because we have some roots showing, but it is DEFINITELY time to start composting here. I couldn't believe how thick and gluey it was. (Our subdivision is only 3 years old, so the land is still suffering the worst effects of having been absolutely destroyed to build, I guess).

Also ready to start a pottery class on the side,


So.App.Mtns., United States(Zone 5b)


Greensand is a sand or sediment that consists largely of dark greenish grains of glauconite, usually mixed with clay or sand. Seems there are three main places that mine Glauconite(greensand) in the United States, they are New Jersey, Texas and Arkansas. It is a natural mineral that opens up tight soil and binds the loose soils.

Greensand is mainly potash and a hydrated silicate of iron. It releases it's nutriential benefits through a exchange action in the soil to be taken up by the plants. The mineral has been used for decades which contains a huge amount of Potassium and other trace minerals(as many as 30).

Recommended application of greensand is 2-4 pounds per 100 square feet or 1 tone per acre.

The Jersey greensand contains 20% iron oxide and 7% Potassium(Potash). The ancient sea deposit is a slow release of Potash and the other essential minerals. Since the 1700s greensand has been used as a fertilizer and soil conditioner that looses clay soils and also increases the water holding capability of the sand and clay. Found when added to any soil will increase water holding properties.

Texas greensand also known as glittergreen holds pretty much same properties as New Jersey greensand. Potassium and iron soil supplement recommended for a mulch, conditioning additive or top dressing. It slow releases nutrients, loosens soils and holds water.

In Arkansas greensand is found in Nacatoch and Ozan formations, which extend from the Arkansas-Oklahoma border to Arkadelphia. Here the glauconite is in a sandy marl that can be 2-10 feet thick and be as pure as 50%.

Greensand is non-soluble in water but will not burn plants. Safe to handle and is odorless and best of all can be applied anytime of the year.

Shenandoah Valley, VA(Zone 6b)

I've used coir (in place of peat moss), decomposed straw and grass clippings, and greensand. So far so good; I'll report more later. I think a modified lasagna method can do well on clay, as well as broadforking the base soil.

St. Louis, MO(Zone 5b)


Can you tell me what Coir is and what it's supposed to do? I really don't want to use peat myself.


Linden, VA(Zone 6a)

Coir is coconut husk fibers. The hanging basket liners you see are coir. I use it whenever i have to chance to substitute it for peat at an affordable price; but haven't found yet a reliable source for large quantities. Maybe somebody else knows a source? It does seem to be becoming more and more available at least as a component of other products such as seed starter mix.

Shenandoah Valley, VA(Zone 6b)

I get it at Countryside Natural Products in Fishersville, VA. First discovered them at their display at the Piedmont Small Farm Festival in the Plains when I lived up there.
I paid $4.95 per block (1/2 cubic foot bale; 11lbs). "100% biodegradable growing medium derived from the coconut husk. Naturally rich in nutrients, with a pH range of 5.5 to 6.5. Each bale will expand approximately 5 times when wetted, yielding nearly 2.5 cubic feet. Coir is a renewable by-product, unlike the peat moss that is being depleted."

Linden, VA(Zone 6a)

Thanks, Zeppy. That'd be much easier to tote around the garden than the 2.8 cu. yd. bale of peat, too. Saves not only the environment, but my back! :)

Shenandoah Valley, VA(Zone 6b)

Hey, Mick, I forgot to mention that you have to add the water to it in a big bucket or the wheelbarrow and let it sit for a day to expand. So it's a little bit of a pain, but not bad....

Linden, VA(Zone 6a)

Thanks Zeppy for all the info. I looked at the Countryside Natural website and they look worth making a trip for. I'll just use the excuse of going to the Dayton Farmers' Market, a trip my DH is ALWAYS up for!

Atlanta, GA(Zone 7b)

Lighter colored clays are typically a sign that the area has been flooded a lot in the past (which is probably the case since you're probably on an old flood plain near the grand ol' Mississippi). I'm not sure if this has to do with nutrient washout, but this is what I've been told. We typically have a lot of red clay here in the southeast, which when amended with lots of organic matter makes a beautiful loam that would be hard to accomplish in a sandy soil. However, in your circumstances, I'd suggest doing a raised bed.

(Zone 2b)

I have the worst clay soil on this planet. I was digging down deep in a area to ammend the soil when I saw just how bad it is. It's perfect for a pottery class. When I got down about 8 inches, the color went from medium brown to a lighter tan! I was disgusted.

8 inches of topsoil sounds pretty good to me. It's completely normal for the soil to change in appearance once you dig down past the topsoil - even in very good soils. Soil formation happens from the top down, and underneath the mature topsoil you will eventually get to the parent material. In most soil types there will be one or more layers in between - partially formed soil or a layer of leached material or that sort of thing. Soils that don't have layers are ones that have been churned around - for example by machines or by the natural cracking that happens in extremely heavy clays.

Gardena, CA

A word of caution: Sand mixed with clay = concrete. that is how they make it. Suggest compost, hay or any other kind of organic ammendments. Try deep rooted plants like dandelions to help break it up and bring the rich nutrients locked into the clay upwards. amend, amend and amend is the most important thing you can do.

Westerville, OH(Zone 6a)

The lazy man's slow-but-sure way of breaking up clay soil: plant diakon (sp?) radishes and do not dig them up when they mature; let them decompose in the clay soil.

Locust Grove, AR(Zone 7a)

YardenMan, can you please explain the daikon solution? Why that particular root vegetable? I'm curious and we do have clay here.

Shenandoah Valley, VA(Zone 6b)

Check out the daikon radish in Plant Files. It's a honkin big root.

Myself, I dump layers of straw, grass clippings, etc. on top. Earthworms go nuts eating, and I'm left with better soil.

Locust Grove, AR(Zone 7a)

I'm familiar with the daikons. Yes, they are honkin big things! My husband loves them as kimchee.

I think I'll give it a try in the fall and plant a couple of rows as an experiment.


Westerville, OH(Zone 6a)

AingieRich: The daikon radishes are the giants of the radish world. They can get to be 4inches or more diameter by 12"-15" long. They are very vigorous growers with massive root systems that break up the clay soil. By not harvesting them and letting them rot in the ground you are accomplishing 2 things: 1) the decomposted radishes add organic humus to your clay soil and 2) the "holes" they leave behind have the same effect on your flower bed as when core areate your lawn.

Locust Grove, AR(Zone 7a)

Thanks YardenMan! You talked me into it and I'm adding them to my seed list.

Midland, TX(Zone 8a)

Keep a big barrel of alfalfa tea going at all times. Drench your soil with the tea, dregs and all. Keep doing this all of one growing season, and keep the entire area you are treating moist. Compost with leaves--preferably shredded, but have lots of twigs and coarse material mixed in to keep it aerated. The microbes and the worms will do their thing and turn your clay into loam. This is the same as amending with organic materials but faster--much, much faster. You can also throw in some garden soil or manure into your brew for even more microbes.

The key to handling this tea--and actually enjoying it--is not to let it ferment beyond the point that it begins to foam on top. Stirring occasionally is good, but judge its readiness by that time that you find it foamy on top when it has not been recently stirred. It will not smell bad at all. It will smell like alfalfa (well, if you add manure, it might smell like a barnyard). Do not put a lid on it. Put a screen on top if you need to keep varmits out, but I don't even find this necessary as the tea will be done in 12-24 hours during the heat of the summer--maybe as long as 5 days in cooler spring or fall weather. Letting it brew beyond that point that it begins to ferment (bubble) is what causes the brew to get rank. The prolonged brewing develops into a tea that gets increasing colonies of anaerobic bacteria, and that's what causes the wretched odor. Use your tea when it is fresher and has a higher ratio of aerobic microbes--that's what your soil wants.

Don't forget to keep your area moist. The moisture plus the microbial activity will bring the worms, and the worms will make your soil. You can even go ahead and plant in your clay as long as you make big planting holes and backfill with the clay plus equal parts of fluff. I use potting soil for the fluff. You could also use spanghum peat and some perlite. If you use potting soil, buy the cheapest stuff you can find. You don't need nutrients in it--just the fluff. The amended backfill will provide a decent growing media until the worms and the microbes do their thing to the native soil as you condition routinely with the alf tea. Of course, you will want to drench your planting hole with the tea before and after back filling.

Continue adding the tea to the soil directly around your plants (and on the foliage while you're at it) every 4 weeks, but keep drenching the unplanted areas as often as you can make the tea.

Purchase the alfalfa pellets at your local farmer's co-op--about $6.50 for 50 lbs. This is the stuff they use for horse feed. Don't use rabbit feed--it typically contains additives you don't want in your soil. If molasses is an added ingredient, that's good. The molasses will help feed the aerobic bacteria and keep the aerobic:anaerobic ratio high, and this is good.

Happy gardening,

(Zone 2b)

The microbes and the worms will do their thing and turn your clay into loam. This is the same as amending with organic materials but faster--much, much faster.

This isn't quite accurate. 'Loam' and 'clay' have nothing to do with how much organic matter there is in the soil. They are texture classifications based on the percentage of clay particles, silt particles, and sand particles in the soil. A soil must have at least 50% sand and no more than about 27% clay in order to be classified as a loam. Even to be classified as a 'clay loam' or a 'silty clay loam' it could have no more than 40% clay.

Changing the amount of organic matter will not change the texture from clay to loam or anything else. Microbes and worms cannot change clay particles into silt or sand particles, so they also will not alter the texture. Amendments such as manure, compost, 'teas', pellets, etc. will not alter the texture. Adding organic matter and having earthworms will likely change the structure of the soil, making it more crumbly and less dense, and breaking up larger clods of soil, but it will not alter the texture. The only way to alter the texture is to alter the percentage of clay, silt, and sand, which is usually not practical.

Josephine, Arlington, TX(Zone 8a)

It seems to me that we are getting stuck between the differences of structure and texture.
Actually, for the purpose of organic gardening, it really doesn't matter if we alter the texture, or the structure, as long as the soil is soft and friable, has lots of organic matter, and can be worked easily, that is what we really after.
If the soil is healthy, it will suppot abundant plant life.
I think that the advice that Penzer gave is very good, and works very well.

Midland, TX(Zone 8a)

Thanks, Frostweed, for your comments, and I'm pleased you found my post useful, but I do stand corrected.

I will change my quote to...
"The microbes and the earthworms will do their thing and change your clay into a worthy media for gardening."

How's that, Spectrum? I note that you are a soil scientist, and you are welcome to correct my rants at any time. This whole matter of soil science is fascinating to me, and I wish I had more formal education in this area. I would be very interested to hear your recommendations for coping with clay. I live in West Texas, and we typically have only a thin layer of alkaline, clayey topsoil on a caliche base. Alfalfa tea has changed my life, but I am still inclined to grow only those plants that are known to tolerate our soil. The difference is that now my plants thrive, whereas before they merely existed. Replacing my soil is out of the question. I'm determined to cope with the native soil.

Hey, I note that you did not take exception to my term "fluff". How's that for amateur nomenclature? ;)

(Zone 2b)

Sounds better :) 'Aspiring soil scientist' might be a better description. I didn't actually notice the word 'fluff' :) I tend to read less carefully towards the end of posts. But it's not a scientific term anyway, so you didn't use it inaccurately :)

Interestingly enough, clay soil is valued here because it can hold more water than lighter soil textures. We have a semi-arid climate and generally need the soil to hold as much water from snowmelt as it can. And it doesn't wear out cultivator shovels and openers as quickly as more sandy soils. However, it does have the drawbacks of requiring more horsepower in machinery and being susceptible to water erosion and 'crusting' which can cause problems with seedling emergence. And there's also the possibility of large cracks causing problems with machinery - breaking axles and that sort of thing.

Around here, it is suggested that people leave lots of plants (roots) in the soil to protect it from water erosion. That also helps to prevent some of the crusting. So, instead of cultivating the old crop under, direct seeding into stubble is a better option. Of course, that doesn't always work so well for gardens. Mulching might be a reasonable alternative. Growing plants that like whatever soil you have is always a logical decision :)

When you say 'alkaline' are you referring to pH or to salinity (patches of white on the surface)?

Midland, TX(Zone 8a)

Our soil is high pH. I assume that's because of lime leaching from all the rocks and the caliche base. Caliche is sometimes no more than a few inches beneath the surface. One does not plant acid-loving plants here except in raised beds or containers or unless one is prepared to treat routinely with chelated iron. I have read that there is no way to permanently change the pH of soil in any significant way, but I am guessing that the alf tea drenches I apply tend to neutralize it, much as a compost heap neutralizes over time.

Oddly, our clay tends to drain well, but I am guessing that is because the soil layer is so thin. I would think as soon as the water reaches the gravelly caliche, it just trickles on down to China. Wish I understood more about these things. I can water my beds till they're boggy in the evening, and by the next afternoon they're already baking again. I guess it's the aridity and this blistering West Texas sun. Mulch helps a lot.

The main problem with our soil is that it is so tight. A plant must have great vigor to establish roots in our native soil. I have some young crepe myrtles really struggling to get established. No matter how much water I apply, the leaves turn curly and crispy, and this is a tree that is supposed to love the heat and tolerate drought. I can imagine that they are just not able to take up enough of the water that is being applied. I backfilled their holes with good stuff, but I was not able to make the holes very deep because I hit that dreaded caliche. Every time I apply the tea, these little trees put on a great show of new growth, but the new growth soon gets crispy, too. They're trying to bloom now. Wish I knew what I could do to help them. Any ideas?

(Zone 2b)

Hmm. The alkaline part sounds similar to here - our soils generally also have a high pH, due to the fact that many are calcareous. Typically somewhere between 7 and 8, although sometimes higher in certain soil types. We also don't plant acid-loving crops (like blueberries) and need to apply iron to some fruit trees - apples especially. Changing soil pH is difficult, especially in a well-buffered soil that contains a lot of carbonate. On the plus side, it means that the soil is more resistant to the effects of acid rain :) Minor/localized/temporary changes in pH can happen with the addition of certain fertilizers (eg - sulfur), peat, some seed innoculants, etc. Manure addition will slightly lower the pH of an alkaline soil. But usually not in any really significant way.

As far as the hard layer goes, that's tough to deal with. If it's just a layer of hardpan with looser material directly underneath, deep tillage may temporarily break it up. But if it's a really thick, dense layer then I'm not sure just what would help. Around here, we use that sort of land for pasture rather than for crops (or gardens). And what usually grows best is native grassland plants that are well adapted to just that sort of soil.

Marlow, OK

I have the same soil here in oklahoma... Nothing but sand and clay.
I dig holes/trinches down to the clay and mix the top soil/sand with compost from my worm beds. Lotta work but it is the only way here to grow anything..

Hillsboro, OH(Zone 6a)

I was going to start a new thread but thought my question might fit in here. I am accustomed to heavy red clay and have learned to deal with that. I just bought a farm a dug a hole 10x15x3' deep. I dug it out with a bobcat. After I went through the sod and topsoil, I found that everything under that is crumbly gray clay. You can form it into a nice ball then crumble it back into dust. If you run it over with a bobcat, it turns to cement but will go back to dust if you hit it with a shovel. How do I deal with that? I have not done a perk test yet but that is next on the agenda. Has anyone worked with this kind of soil?

As the area holds water, but does not flood, I know I need to build up anyway to save roots sitting in cold wet soil in the spring. Anyone have any tips?

Bloomingdale, NY(Zone 4a)


I farmed in clay soil; actually clay and rock. Our kitchen garden consisted of double-dug raised beds with a (semi) permanent mulch. The market gardens were mostly wide rows on the flat in which I tilled in many tons of woodchips and leaves. (Most days after work I stopped at the town garages and filled the pickup with a load of chips. I did this for years.) I also had good results with growing buckwheat as a green manure crop. When we sold the place some ten years later, the soil was hardly recognizable as the rocky clay we started with.

There are legumes that will add organic matter with the added benefit that roots penetrate deeper in to the subsoil and you get some free nitrogen.


Hillsboro, OH(Zone 6a)

Thank you very much for your reply Wayne. I know I have lots of work ahead of me. :)

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