Help! How do you deal with clay soil?

bebe_ct(6a)May 15, 2011

Hey there everybody,

I'm a fellow gardener from New England and I'm trying to help Dad with his garden in central TN. The biggest obstacle for him is the clay soil. He's already killed plenty of plants due to the fact that he's only familiar with gardening in New England soils which are very different from TN.

Can any of you recommend any websites and/or books that would help me choose plants for him that would do well in clay in TN?

Thanks in advance for your suggestions.


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Your dad---and you, if you're not still in New England---should come to the Middle Tennessee Plant Swap next Saturday, May 21th, at Henry Horton State Park. There's a thread right here on this forum about the swap.

Newbies are welcome, and trust me, even if you have nothing to swap, you WILL go home with plants. (*grin*)We start at 9 AM, and share a pot-luck lunch around 11. Then we have a speaker, lastly we put all the plants we brought but don't want to take home in one spot, and people are encouraged to help themselves. These plants should be good choices for your dad's garden, because they come out of gardens right here in TN.

    Bookmark   May 15, 2011 at 12:34PM
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brandon7 TN_zone(7)

Clay soil can be an excellent soil to grow a wide variety of plants. Clay soils usually retain moisture well and tend to be more nutrient-rich than other soil types. Problems can occur if drainage and aeration is not satisfactory. A lot of the issues you dad is having may be related to where the plants are placed (moisture conditions at the site). Raised beds (with well-draining soil) are often one of the few practical solutions if finicky plants are desired in a location where drainage is not adequate. Amending the existing soil can often make matters worse by actually increasing drainage problems (sometimes referred to as the bathtub effect).

More details about what he's trying to grow and conditions at the site may be helpful in further recommendations.

    Bookmark   May 15, 2011 at 12:39PM
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Starting a compost bin might not be a bad idea to help whatever you plant along. Just don't put yours in the shade like I did mine. We built ours from cinder blocks. There are some good, 2 cubicle, plans on the net for compost bins. The rich, dark, loamy stuff just seems to suitable for the garden to me. Our soil is a little clay like too.

It'll take a few months to get the compost bin producing a good amount if you do nothing but add kitchen scraps (learn which can't be added) a source of carbon and a source of nitrogen (I think it's nitrogen...tired and just learning this myself.

Ours has been going only a bit over 3 months with no loamy compost yet but lots of worms underneath and we didn't chop things up well. I'm still reading on the finer details of this. A lot of different ways to produce compost apparently (we aren't using any manure, which is another way).

Boy, those who do compost well have some very nice looking material to amend with it seems to me.

    Bookmark   June 1, 2011 at 9:46PM
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Check out books by Judy Lowe - she's written several region-specific books.

Another one I like is "Tough Plants for Southern Gardens" by Felder Rushing. He has a cute, funny writing style - kind of a "no bs" type. :)

Here is a link that might be useful: Tough Plants for Southern Gardens

    Bookmark   June 2, 2011 at 1:16PM
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heathersgarden(6b/7a Mid TN)

My 2 cents:

+ Natives adapted to our soil

This has been a winning combo for me, and now seven years later I can grow all sorts of goodies that would've just curled up and died in the early years.

    Bookmark   June 2, 2011 at 4:42PM
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Hi heathersgarden,

How would you feel about starting a thread on composting sometime?

There seems to be a learning curve involved and the internet has so many different techniques to use that it just seems to complicate it all the more.

    Bookmark   June 2, 2011 at 11:23PM
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heathersgarden(6b/7a Mid TN)

AesSedai, you're right about there being almost too much info on the web concerning composting. I've composted for years, and I just keep simplifying as I go. Once you gain some experience and the understanding of the science behind compost, it'll become like second nature. Like cooking!;)

Here's what I do currently: As I weed, trim, deadhead etc, I throw it either directly on my beds or I throw it onto the lawn to be shredded by the mower*. Unless I've treated my lawn with chemicals, I can bag those clippings to spread onto my beds, or just mow it in to feed the lawn. I even run over small branches with my mower because my goal is to return all the nutrients my soil helped produce going right back to the soil. It can be hard on the mower (the machine and the husband:)), so we sharpen the blade at least once or twice a year.

*The only exception to this is weeds or weed parts that are unwelcome pests and would cause more problems if recycled back into the garden such as: bermuda grass, any weed seed head, or perennial weed root. I frequently dismantle weeds to keep the good parts for my garden, and only throw away the bad parts.

In the kitchen, I run my scraps through a high powered blender, and then I pour that onto various parts of the garden or lawn.

As my garden becomes more lush and productive, I find myself not gathering as many materials as I used to. But if you need lots of organic material - look locally, be creative, and don't be shy to knock on a neighbor's door to ask them for their bagged leaves or discarded holiday straw bales.

So there you have it - no compost bin, no more turning the compost, certainly no buying any compost. It's working really well for us. I rarely fertilize, I rarely have pest problems, I water sparingly. I do buy mulch out the wazoo cuz it just keeps turning into compost too! I'm a laid-back kind of gardener, but I am religious about composting and mulching.

Now for more opinions, check out the soil and composting forum right here on GW:)

Here is a link that might be useful: Soil, Composting and Mulch forum

    Bookmark   June 3, 2011 at 5:19PM
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rosee bushes, tomatoes(at least in Granger County), blackberries,Crepe Myrtls and many other things I can't remember right now grow well in Tn soil; Mostly I'd suggest going native ,though. Good luck.

    Bookmark   June 7, 2011 at 7:29AM
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katiedidcottage(z7 TN / Chattanooga)

Where I can from, we had a wonderful sandy loamy kind of soil that was really porous and growing in clay was like something just sitting in a clay pot with no drainage and the roots would rot.

I have learned from landscapers to plant the small trees shrubs a little higher than ground level. I dig deep, but fill it in with a good porous soil and some rocks for drainage, leaving about 2 inches above the ground level and then covering it up very tight with the same porous soil and packing it down good. Then I cover it heavily and thickly with mulch and water deeply. I have had no plants die since I started planting them this way and I learned it from a landscaper at a garden show in a convention center.

I also have raised beds for my vegetable garden. Look into Lasagne Gardening. This way your plants will have drainage and the soil will be the soft amended soil that you have put into the beds. I have mostly used the huge bags of Miracle Grow soil, but you can find any soil bagged or not and use it. The soil we had brought in as "top soil" was no good and nothing would grow in it is why I've gone the bagged soil route. The compost pile that someone else mentioned is a good way to enrich whatever soil you have in your raised beds.

I hope this helps some.

    Bookmark   June 7, 2011 at 3:30PM
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brandon7 TN_zone(7)

In some soils, digging a hole and filling it with "good" soil" can actually cause a bathtub-type effect. The hole will easily fill with moisture, but then it won't drain out through the poorly draining soil on the bottom. That can especially be a problem with plants that don't like wet feet. In poorly draining soils, it's often better to either stick with the finer (like clay, for instance) soil or use raised beds.

Also, rocks at the bottom can cause a perched water table (on a small scale). When water drains, it tends to drain from soil with larger pores to soil with smaller pores. So, large objects like rocks or big bark chips can block drainage by creating larger pore spaces around the large objects and locking moisture into the finer soil above.

    Bookmark   June 7, 2011 at 10:30PM
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katiedidcottage(z7 TN / Chattanooga)

Thanks, Brandon. All of our trees and bushes we have planted in a sort of "Raised Bed" fashion have thrived and the ones we planted in holes in the ground have all died, due to the results you described.

    Bookmark   June 9, 2011 at 10:34AM
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How do you plant a tree in "Raised Bed" fashion (other than the obvious of container planting)?

    Bookmark   June 9, 2011 at 10:59AM
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brandon7 TN_zone(7)

Berms (raised beds without sides) work best. Really large raised beds can also be used (especially with smaller trees).

BTW, below is a pretty good guide for planting trees. It doesn't really cover raised-bed planting (especially the fact that different soil can be used), but it does give a lot of valuable info.

Here is a link that might be useful: Planting a Tree or Shrub

    Bookmark   June 9, 2011 at 11:18AM
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Thanks Brandon. You are a wealth of information and I appreciate it! I was hoping katiedidcottage might share details or a photo of their trees in "sort of "Raised Bed" fashion".

    Bookmark   June 10, 2011 at 12:30PM
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katiedidcottage(z7 TN / Chattanooga)

We are getting ready to plant a new shrub, so I'll take some photos and share them. We got this plant on sale because it's so late in the season for planting, so I don't know if it'll make it or not, but I'll show you how we do it any way and then try to remember to let you know later on if it makes it. :) Also, maybe if Brandon can see something that we did wrong, he can point it out at any stage what could be a better way to do it.

    Bookmark   June 12, 2011 at 1:28PM
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brandon7 TN_zone(7)

I'll watch for the thread. If it's a pot-grown shrub, planting this time of year shouldn't be a problem, especially if you keep it watered properly, afterwards. I've planted quite a few trees in the past month (with no losses yet).

    Bookmark   June 12, 2011 at 5:29PM
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katiedidcottage(z7 TN / Chattanooga)

I am going to try to post the pictures I made last evening while planting our new shrub. The link is below. Since I couldn't add any description in Photobucket, I'll try to describe the pictures here. Brandon, please tell us if I did anything incorrectly.

1. Prepare the ground by removing the top layer of grass.

2. Further prepare the ground by chopping down into the soil a few inches making it loose.

3. Add a layer of the soil you are going to use. In our case, we are using Miracle Gro soil with moisture control.

4. Remove plant from pot if it is in one and loosen the roots slightly.

5. Pack the remaining soil tightly around the root ball creating a pyramid type structure tightly around the root ball to the top of the soil of the root ball.

6. Add mulch to the surrounding pyramid by packing the mulch tightly to the soil.

7. We also are adding pine straw to the top for protection from the heat and to distribute the rain impact more evenly should we have heavy rain.

As I said, we have had very good luck planting our trees and shrubs this way. We had hard clay soil when we lived near western Tennessee and now that we are near eastern Tennessee, we have chirt which is nothing but rocks with a little dirt mixed in - almost impossible to dig into.

After a few years the plant seems to be part of the earth and you cannot tell that it is packed up above the ground. It seems to reach its roots down and become part of the earth.

Here is a link that might be useful: Planting a shrub or tree

    Bookmark   June 13, 2011 at 11:02AM
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brandon7 TN_zone(7)

I hope you will take my comments as they are meant (to be helpful) and not as overly critical. I wish I could just say "way to go", but that wouldn't be truthful or helpful. So, anyway, here is what I see...

There are two things that would worry me significantly about the planting method.

First is that the type of soil you used isn't real soil (mostly, it's peat moss and composted bark) and won't hold up over the long run. After a few years (maybe 5???), the ingredients of the Miracle-Gro will be broken down and "eaten" by the native soil. This will leave your shrub depending only on the native soil and with part or most of it's root system above ground. It may still be able to survive, but certainly no better than it would have been able to if it had just been planted a little high in the native soil. The Miracle-Gro soil will also be poor in nutrients after a short time (probably just a few months). Maybe the shrub can grow enough roots down into the native soil to compensate, but this will be hurdle it will have to overcome. Another problem with using this type of medium is that there will be a sharp interface between the planting medium and the native soil, which (even with the surface preparation) will likely discourage some root development down into the native soil. The moisture-control part of the Miracle-Gro may contribute even more to discouragement of root development into the native soil.

The second major problem is the size of the mound/berm. If I was using any type of soil other than the native soil, I'd provide a berm large enough to hold either a significant part of the expected size of the mature root system, or, large enough to hold at least a few years of root growth and tapered very gradually off so that roots have every opportunity to grow down into native soil. The example here would encourage a poorly formed root system (almost like pot-bound roots) and eventually girdling roots. It would be highly likely to lead to eventual mechanical failure in the case of a larger growing tree.

A third possible problem (which would only worry me if I found it to be a problem) is poor drainage of the planting medium because of the combination of moisture-control, mulch covering, and poorly draining soil underlying the Miracle-Gro. Whether the berm would stay too wet depends on too many things for me to really accurately predict, but I would keep an eye out for this problem.

I would recommend that you get some good quality topsoil and mix that with your native soil to form a shallow but broad berm to plant in. I think that would lead to much better root establishment, better drainage, and a long-lived plant.

    Bookmark   June 16, 2011 at 11:19AM
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katiedidcottage(z7 TN / Chattanooga)

Thanks, Brandon. I wish I could find some "topsoil" or any kind of soil for sale where I live. We looked high and low a couple of years ago and asked many people and finally bought a truck load of this stuff from a dirt place called "Garden Mix" close to downtown Chattanooga that looked pretty promising for our raised bed gardens. It was "highly recommended" and pretty expensive also. It looked great, was dark and rich in color and seemed to be loose and easily worked with. After one year, this stuff turned to a hard sterile packed hard as a rock mess in our nicely built raised beds so that the bottom of what is in our beds in now about 6 inches of a hard sterile packed layer. We have a hard time even breaking it up with a shovel now and we had mixed it with several bags peat, manure, and other bags of "topsoil". So since then, we have had to build it up with the only thing we can find close to something to grow in which was miracle grow. There are no nutrients at all in the native soil. We are in a house about 6 years old and the yard has been built up with this sterile chirt which is mostly small to medium rocks from about 1 inch to 3 or 4 inches wide. Grass will hardly grow in our yard unless we fertilze like crazy. It seems that everything we've planted is doing well and most of the time we have mixed some of the chirt in with the miracle grow and the plants seem to be doing well. If you can imagine this: 5" of what we dig out with post hole diggers (the only way to get into this chirt) will result in a small pile of small rocks with at least 3 of the 3" to 4" rocks and just barely enough dirt (a clay that does break up some when dry) to fill in the spaces between the rocks.

I certainly do appreciate your criticism and will keep it in mind when I plant anything else.

If you or anyone else knows of any place near Chattanooga to get any topsoil, it would be greatly appreciated. I would have to start out with a wheelbarrow full to see how it worked because after my other "highly recommended" pick up load of "Garden Mix" that was sterile and hard as a rock after the first growing season, I have my doubts.

    Bookmark   June 17, 2011 at 5:40AM
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