Sand and Clay
Question from Irene:
I have had a huge perennial garden for ten years. It was clay.It was once beautiful, had garden parties. Every year, in the spring, I incorporated the bags of tube sand from winter into my soil, (pleasantly happy with myself for “enriching my garden soil” to what I believed was helpful to my garden). To my dismay, my garden plants started to dwindle. I saw the soil hardening to cement boulders, cracks in the soil, couldn’t even drive a shovel into, and even with the addition of truckloads of manure, and the addition of four compost piles filled with worms spread (thinly) throughout, I was still disheartened with the “roll Off” effect of watering. I even went so much as to replant my garden, pot all of my favorites and add wood chips, peat, and compost to fix my soil.I do not know how to fix what I have done. I have failed my garden and myself. I cannot find an answer. Soil test? Replace soil? How does one go about making a wrong a right? Cannot find a site for my wrongdoing. Any
suggestions?
Photo by F. D. Richards
Answer from Pat:
The only suggestion I have is to bulldoze off your ruined soil and haul it away in trucks. Then replace it with truckloads top soil, but be sure to mix the lower levels of the replaced soil with the soil you have so you do not create a horizon between the two, thus making a buried layer of hardpan, which could stop roots. If you live in an area where the soil is alkaline, adding gypsum to the clay soil below would also help but it will not help the clay you have mixed with sand, because in that case you changed the structure of the soil, which means the size of the particles that are in it and the way they work together. As I have said many times we must never try to change the structure of our soil but only improve what we’ve got with organics.
I am truly sorry to hear about what happened to you, but I have been warning gardeners for many years against the dangerous practice of adding sand to clay or clay to sand with the hope of improving it. You didn’t know the harm you were doing, so you cannot be blamed. But there are some people who fall into the same trap because they simply will not listen to my warnings or they do not believe me. Witness some of the letters I have received from guys—mostly guys!— arguing with me. All that I have stated, however, is based on scientific research that was done many years ago by the University of California and the Agricultural Extension. These facts were taught to me by a Farm Advisor many years ago when I first became a garden writer. Over 30 years ago he took me under his wing and used to come to my garden and sit with me over lunch and tell me much of what he knew. He wanted me to communicate to the public with truths he had learned from agricultural school and research. This was long before there were any Master Gardeners. I wrote a popular garden column and he figured this was one way to spread his knowledge since I knew how to write and make things interesting to the public.
Though your story is a sad one, you have done me a favor by sharing it, since you have put a human face onto a sequence of events that I have been trying to explain for many years.
Photo by National Garden Clubs 
Taking your advice. Have been planning on removing ruined soil and replacing. For my situation, bulldozing cannot be done, as I have established ornamental trees and shrubs within beds, PVC water lines under lawn and one inch pavers for my walkway. Working on details. Thank You very much for the time you took to respond, and so quickly! I look forward to seeing my garden thrive and having a garden party this year.
How kind of you to write back! Since you have an extensive greensward, of course you cannot bulldoze, but working alone for 10 years digging sand into your clay you probably did not mix in the sand deeper than the length of your spade. Seeing your landscape, I could visualize how you could have one bed or portion of a bed dug out to that depth at one time creating a ditch which you could then subsequently refill with top soil and so forth around the entire garden until all was done.
My only concern is layering the new top soil over the native clay soil beneath, especially if the top soil you get is not clay based so I’m going to change my advice about mixing some of the top soil in with the clay on the bottom of the trench. It would be better to mix composted organic soil amendments into the clay on the bottom of the trench before you replace with top soil. This would be better in case the top soil is sandy. That would be repeating the same error as before! If you can find top soil which is made of amended clay, this would be ideal since there would be little difference between the soil above and that below. I know a man who bulldozed off his entire property of clay soil and replaced all of it truckloads of premium top soil, which was probably amended river silt. His garden grew well for forty years, as long as that man lived there, but the soil was so deep that he never dug the buried clay soil beneath into the amended top soil above.
Firstly, I wanted to apologize for writing, again. I hope I am not being obtrusive to your time or knowledge. It is just that no one that I know is so deeply in love with the delight of gardening as I am, so they couldn’t help with my situation. (In fact, I am the one whom gets their requests to help them with their outdoor space). So, this is why I initially contacted you, and why I keep writing back. I only want to have, once again, that feeling of the sense of accomplishment that all of my work in my outdoor space provides beauty in thriving plants with happy faces, and mine. If I am wearing you a bit thin, I understand. Please let me know if I am. I hope you are willing to help me fix this with your experience as it plays out, so I can share it with somebody!!
Secondly, not sure if I have ever seen any soil offered with clay in it. People must veer from that as Northern Ohio is clay. Mostly, I find a “grandeur” label like premium garden blend, that is 1/3 humus, 1/3 sand, 1/3 compost. Or something of the like. I have access to my four compost bins, horse manure, my worm farm rewards, pine needles, straw, leaves, peat, and more. If I added these gems to the clay before topping with said “grandeur”, would it be correct in assuming that I mix them with a mantis (tiller), and not just create a layer? How much per foot? Wouldn’t the organic additive just break down over time and create a bi-layered garden bed? Should I try to find a topsoil without sand? I am not against adding any organic substance to whatever I order (ie: organics). I suppose it all boils down to the terms of what I need in regards to the term “topsoil”. Can you help with what I need to understand? Irene
As a side note,… I have requested the help of two brawny men whom I work with, that are willing to wheelbarrow said topsoil, and I cannot wait to see the one of those two in a T-Shirt!! Hope it is too small for him.
It’s true I am unbelievably busy and have many irons in the fire, but I am committed to writing this blog and communicating with people like you who love gardening. I like helping people solve their garden problems.
Thanks for the new information you have given me. It sounds logical that no company sells clay-based top soil. Hence I am changing my advice to the following:
1. Have your two brawny guys dig out and haul away all ruined soil you mixed with sand.
2. Haul in the same kind of clay soil from your own property or from your neighborhood and mix it with a lot of organic amendments, well rotted compost, peat moss, etc. (Don’t add dry carbonaceous materials however. It must be properly composted.)
3. Replace removed soil with this mix of amended clay.
4. If you cannot find any clay fill, simply add a lot of amendments to the soil you have got. It looks as if your beds were mounded up. They may end up flatter but that is okay. Gradually they will mound up again.
We have had a few similar clients that have combined the dreaded sand & clay creating a “cement” soil. (Cob building anyone?)
We have a compost-tea/extract product called Soil-Restore which is a combination of: compost, worm castings, wood chips, humic acid, mycorrhizae,glacial rock minerals, and liquid fish & kelp. This combination adds TONS of beneficial biology, organic matter, minerals, and LIFE back to your soil. I am unsure where you’re located and if such a service is available in your area, but what we do is come out and drill (yes, drill) into the rock-hard soil about 3-5ft deep and inject the compost directly into the root zone of the tree and broadcast the compost-tea on top of the soil. For problem landscapes like yours, we would add mulch and worm castings/compost on top of the soil. We Soil-Restore 3-6 times a year and have completely turned around landscapes and saved declining oak trees!
Pat,
In your book you recommend adding 15%-20% Profile Professional Soil Conditioner, which according to the manufacturer, is sold under the trade name of Turface MVP. I am in the process of reworking all flower beds by adding Profile and Growmulch to achieve a mix of 40% soil, 40% Growmulch, and 20% Profile in the top 6 inches of soil. Any comments?
I took out my recommendation of Profile from my last and latest edition of my book,which is called “Pat Welsh’s Southern California Organic Gardening, Month-by-Month”, published in 2010 by Chronicle Books. Please refer to the current edition. You are using an old edition I wrote 13 years ago that was published in year 2000. Agriculture and gardening changes just as other sciences change. Change is brought about by more research. I think this is too much Profile. Follow package directions. Also, I have changed my mind about this product since using it myself. I think it’s best for lawns and definitely works well there, since it is used by golf courses with great success. I don’t think it works long term in flowerbeds, nor as well, since we dig them up all the time and this may break it down. My recommendation for amending soils is to amend with 4 inches of organic compost, such as Gromulch or other bagged brands or trucked compost and dig that into the top one foot of the soil and after that fertilizer goes in the top 6 to 8 inches. If you have heavy clay also add gypsum. If you have sand, wetting agents may also help.
I’m glad I found this article. I was thinking of adding french wells: simply using a post hole digger for 3-5 feet and filling with sand in areas where water is accumulating. Would this have the same disastrous effect?
Yes, your plan would have a disastrous effect though not for exactly the same reason. It sounds as if you were planning to build what is technically called a “sump.” (There is no such thing as a “French well.” The correct term is “French drain” and this is totally different from what you describe and it works well. See below for description.)
Basically, a “sump” is a hole in the ground usually filled with gravel (not sand.) Gardeners make sumps under planting holes without knowing that this has long been a failed technology. Out-of-date garden books sometimes recommend this discredited idea and so do some gardeners who don’t know that sumps are a failed technology. Tests have shown sumps never work and actually make drainage far worse since instead of draining water away, they hold water. When you build a sump you are basically creating a buried swimming pool for roots. Plant roots go down to find water. They find the water in the sump and die from root rot. Sumps usually kill plants.
One effective way to increase drainage in a bed that does not have good drainage is to build a raised bed. This method can increase drainage on flat ground. Raised beds do not have to be very tall to be effective. Even 4 inches tall will work if the bed is wide enough. Fill the raised bed with native soil or top soil and dig through the soil at the top into the soil below to plant a tree or shrub. Before filling the raised bed with top soil, always mix some of the fill dirt with the soil below in order to create a “marriage” of soils so you do not create a hard line between two different types of soil.
Another way to create drainage where there is a lack of it is to build a French drain. A French drain is a trench that slopes downhill from the area of poor drainage to a place at a lower level on the property. To build a French drain, first dig the trench making sure the floor of the trench slopes downhill to an exit. Next line the trench with landscape filter cloth, then lay 8 inches to one foot of gravel in the bottom of the trench. Place a drainage pipe with the holes facing downwards or to the sides onto the bottom of the trench. Always place the pipe so that holes are on top or the sides of the pipe or it will eventually clog with earth! Fill the trench with 2 or 3 more feet of gravel. Close up the the landscape cloth over the gravel and then refill the trench with one or two feet of native soil on top. Replace the lawn or other landscaping on top.
When the lack of drainage is caused by the alkalinity clay, then you can increase drainage on clay soil by digging about half a coffee can full of gypsum into the bottom of your planting hole. Gypsum causes a chemical reaction in the soil that breaks up clay particles. However, if you do not live in the West this might not help. Gypsum increases drainage of clay only if the fact that it does not drain is caused by alkalinity. In the eastern USA most soils are acid. In the dry West, most soils are alkaline.
When the lack of drainage is caused by a layer of hardpan buried beneath the topsoil, it is sometimes possible to dig a hole down to the hardpan and then break through the hardpan to a layer of earth lower down that drains. You would then fill the hole through the hardpan with gravel. In this case you are not building a sump but an actual drain that lets irrigation drain out of the planting hole into a lower level of soil that has good drainage.
Dear Pat,
I used to have heavy soil (clay)? but over the years it has turned sandy, what is the best and faster amender. Is there a fast fix for a situation like this (I am 86 ). This land was originally terraced from raw land.
It was full of gophers, so when I had the terracing stone-walled, I had the men lower chain link to keep the gophers out. This worked, but 40 odd years later the soil is no longer heavy, but a consistency of sand–not sand, but light and easy for hand work. It is difficult to get at these terraces with big equipment, hardly any company owns a channel line to get products/emplements down to the garden area. That withstanding, I need to know what to do for the soil. My first thought
was to see who could deliver a massive amount of manure. This would
feed it and return its texture–not the answer? Please help
Sounds as if the land you are describing is like a river bed or subject to erosion of sandy soil washing down from above and covering the clay layer beneath it. Yes, adding horse or cow manure is a wonderful way to improve sandy soil. Growing a cover crop and digging it into the soil is another way to improve the texture, water retention and nutrient content of sandy soil.
This is a PS: I am a year older than you and still going strong. Most likely people like you and me will go on and on so might as well do whatever to improve our ground. There might be no rush!
Re: your soil again: Your light soil sounds like silt. Perhaps the clay layer was not deep. Possibly the gophers, if there were as many as you describe, had an effect by bringing up another soil type from below when they were building their mounds. Perhaps this lighter soil layer from below now lies on top of the clay.
I didn’t do my research,and already added sand to my flower garden.(plants not in yet). Now what can i do to fix it? I have compost and topsoil. Please help.
Does this mean you mixed sand into clay? I have tried to warn people not to do that. If you have already done it, I have not yet thought of a solution. Perhaps you should amend with organic compost and if nothing grows there due to lack of drainage, then build raised beds or terraces on top and fill with top soil. Applying gypsum to the clay might be slightly helpful.
Also reference this post and comments for more information – Never Add Clay to Sand or Sand to Clay.