Clay Soil: A Real Challenge

By Toni Leland (tonileland) April 28, 2008

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For a potter or sculptor, abundant clay soil is Nature's goldmine. Thick and sticky, its natural strength and water resistance are prized by artisans, but despised by gardeners.

Learning to work with this native soil is the secret to nurturing many beautiful plants, shrubs, and trees. Familiar clay-loving plants include Black-eyed Susans (Rudbeckia), Canna (Canna), Joe-pye Weed (Eupatorium), Purple Coneflower (Echinacea purpurea), and Sunflower (Helianthus), to name a few.

Why is clay so difficult for gardening?

Of all the soil types, clay has the most minute mineral components; when wet, clay is slippery and slow to drain; when baked in the sun, clay becomes hard and unworkable. Clay is the last soil to warm in the spring.

On the positive side, clay has high levels of nutrients and will support many more specimens than one might think.

How to survive a clay landscape

Preparing the planting site and maintaining hydration are the key steps in enjoying a satisfying relationship with clay. Plan your planting for spring when the soil is most workable; be sure to wait until ground temperatures warm up and excess moisture has drained, otherwise you'll end up with clumps and clods. With clay beds, unless you love to till and dig, it is not necessary to cultivate the entire planting area. Decide where your plants will be located, then dig individual holes and amend them with peat or other organic soil amendments. (Pay close attention to the nutrition requirements of the plant; some will not appreciate over-fertilization.) Dig the planting hole much larger than usual to accommodate the amendment and give the new plant some room to establish itself before being required to burrow its roots into the surrounding resistant soil.

When you dig the hole, take a moment to inspect the sides. Note the slick shiny surface you've created. This surface will not allow water to leave or enter the planting hole. The answer? Using a hand-cultivator with 3 or 4 tines, drag it from the bottom of the hole up the sides to form little furrows all the way around. These breaks in the slick surface will allow drainage and absorption.

Maintaining moisture during dry periods is critical; do not allow the top 3 inches of soil to dry out. Mulch is the obvious answer to this management issue. Spread mulch no more than 2 to 2-1/2 inches deep and soak it thoroughly. Ideally, mulch should cover all the planting area to prevent wicking and evaporation. Be sure to keep mulch material well away from the stem or trunk, since the decomposition process produces heat and can cause plant damage. (For more information, refer to my article on Mulch.)

Remember, any new planting - whether it is drought tolerant or simply not fussy - will need TLC for the first season. From then on, you can relax and enjoy the fruits of your labor. So, gardeners take heart. The following partial list of clay-tolerant plants will enrich your landscape, giving you depth and color without many complaints.

Perennials

Bulbs, Corms, Tubers
Canna Lily (Canna spp.)
Daffodil (Narcissus)
Daylily (Hemerocallis)
Milkweed (Asclepias tuberosa)
Miscanthus/Grass (Miscanthus sinesis)
Nearly Wild Rose (Rosa rugosa)
Obedient Plant (Physostegia virginiana)
Oxeye Daisy (Heliopsis)
Purple Coneflower (Echinacea purpurea)
Salvia (Salvia spp.)
Shasta Daisy (Leucanthemum spp.)
Sunflower (Helianthus)

Shrubs
Beautyberry (Calicarpa dichotoma)
Burning Bush (Euonymus alatus)
Chokeberry (Aronia melanocarp)
Deutzia (Deutzia gracilis)
Flowering Quince (Chaenomeles japonica)
Forsythia (Forsythia spp.)
Japanese Barberry (Berberis thunbergii)
Lilac (Syringa vulgaris)
Ninebark (Physocarpus opulifolius)
Potentilla (Potentilla Fruticosa)
Red Osier Dogwood (Cornus sericea)
Spirea (Spiraea spp.)
Swamp Hibiscus (Hibiscus coccineus)
Viburnum Arrowwood (Virburnum dentatum)
Winterberry (Ilex verticillata)
Witch Hazel (Hamamelis vernalis)

Trees
Ash (Fraxinus spp.)
Bradford flowering pear (Pyrus calleryana 'Bradford')
Eastern redbud (Cercis canadensis)
Flowering crabapple (Malus)
Maple (Acer spp.)
Oak (Quercus spp.)
River Birch (Betula nigra)
Willow (Salix spp.)

About Toni Leland   Toni Leland has been writing for over 20 years. She has written a biweekly gardening newspaper column as a spokesman for the Ohio State University Master Gardener program, and writes for Grit magazine and Romance Writers Report. She has been a gardener all her life, working soil all over the world. In her day job, she scripts and produces educational DVDs about caring for Miniature Horses, as well as writing and editing books about this unique height breed.

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Subject: Sand Amends Clay Nothing is BETTER!

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Posted by SeramasunARK (from Batesville, AR) on May 10, 2008 at 1:16 AM:

I have poor rocky clay soil last year I got some top soil. That was a joke it was full of johnson grass and more clay. This year I got river sand. I have never been happier it's the best. No weed seed, and it makes it easy to weed. Broke up my existing raised beds with spade fork and worked sand in. Sand is whats missing in clay. Of course I have compost, manure, and leaves to work with but nothing beats river sand to ammend clay soil. The Best agriculture land is mostly sand. River sand is affordable compared to what's out there and it works better.

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Posted by Fitsy (from Hayesville, NC) on May 10, 2008 at 8:09 AM:

I had given up on getting river sand, but now will
renew my efforts!
Fitsy

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Posted by Flamboyana (from Houston, TX) on May 2, 2008 at 1:55 AM:

My three year, 5 ft. Jatropha only leafs out at the top of its three branches. Like stars on a Christmas tree, lovely red blooms appear on each branch and last for weeks. After seeing photos of several Jatropha bushes in full dress, I wonder if I am not watering it enough or maybe watering too much. It is planted in healthy organic soil, with peat and conditioner. I've also added mulch. It seems strong despite its spindly appearance. Also, it receives a lot of sunlight. I have never fertilized it. I live in Houston, TX where temps are already in the mid 80's. I would appreciate any suggestions/advice. Thanks.

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Posted by tonileland (from Nashport, OH) on May 2, 2008 at 6:31 AM:

I am not familiar with this plant, but if you post your questions on the Texas Gardening forum, I'm sure you'll get some answers. [HYPERLINK@davesgarden.com]

Good Luck!
Toni Leland

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Posted by Bettypauze (from Victoria Harbour, ON) on April 28, 2008 at 4:11 PM:

You've given me hope as well, my back yard is quite sandy and I've put mulch and worked topsoil and flowers are flourishing..

Not so though with my clay soil located in the front shade gardens...will read and re-read your column in hopes of improving this location..

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Posted by coyotee (from Colorado Springs, CO) on April 28, 2008 at 3:12 PM:

The Pikes Peak Rose Society recently had a seminar covering the Texas A&M program to develop hardy roses that didn't need much in the way of care. One of the key components was to use expanded shale when preparing new beds. This is shale (stone) that has been super-heated to "expand" each piece, making a very porous material able to retain water/loosen the soil. More on this can be found at:

[HYPERLINK@aggie-horticulture.tamu.edu]

aggie-horticulture.tamu.edu/extension/newsletters/hortupdate/nov03/Expdshale.html

The techniques developed in this program can apply to pretty much any planting, not just roses. Meanwhile, I thankfully (?) don't have clay soil in my garden - I'm sitting on top of a sand dune. Similar problem - lack of nutrients plus extra care needed for getting water to plants.

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Posted by MistyPetals (from North Augusta, SC) on April 28, 2008 at 1:44 PM:

Great article! My clay soil was the cause of much heartache until I started amending like it was my life's work to do so. When I did, I recognized results over a period of time that are satisfying. Truly, the plants recommended here are the ones I've found to do best in our clay soil. This practice is not for those in a hurry, rather it takes time to get to the point of Wow, it really does work. The good news is after reaching that point, it seems relatively simple to maintain quality soil. Just keep plugging away.

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Posted by Gardendogfriend (from Milwaukee, WI) on April 28, 2008 at 12:32 PM:

I have been amending the planting holes (as described in the article) for 16 years. It really does work. When I plant something, tree, bush, perennial or annual, I make the hole bigger than necessary. I add a mixture of peat moss, vermiculite and manure/compost. Over the years, the soil has improved tremendously. The "additives" gives nutrients not only to the plant that I am planting, but also to the surrounding ones as well.

I just removed some sod to add to my garden beds. The new areas have very heavy clay. I dug some holes to plant new trees and after the rain the water is still there 4 days later. I will try the raking method with the hand rake. Hopefully the water will then drain.

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Posted by zemco20 (from Tipp City, OH) on April 28, 2008 at 11:58 AM:

Thank you!! I have clay soil that I have been fighting for 24 years. The plants that you recommend are the ones that have made it over the years.

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Posted by SuitePME (from Auburn, ME) on April 28, 2008 at 11:10 AM:

My first veggie garden in 2005 in my new house was best situated exactly where the most clay was concentrated. My Dad cautioned me about planting any root veggies but was helpful in his advice for tomatoes, peppers, and other items, but honestly didn't think I would see any results. Lo and behold, 6-7 foot tomato plants by the end of August, pepper plants that yielded so many peppers I just finished the last of the frozen stock, daisies that burst wide open, and green leaf lettuce that unfortunately went all but one harvest to the groundhogs! I made some of the best fresh salsas and sauces I've ever produced and loved every minute of the hard work. I did use some Coast of Maine amendments and also barriers to make the walkways easier to navigate, but other than those, very little extra was done other than watering when necessary.

2006 was far too busy in the office for a veggie garden so I planted a few flower plants, threw in some wild flower seeds and a Buddleia and let it go. Gorgeous, and the hummingbirds and butterflies loved it! 2007 was recovering from a broken fumur so NO gardening extras at all - I called it my year of "Gardening by Butt". Imagine my surprise at the end of the season to find a few pepper plants and two yellow pear tomato plants that took it upon themselves to sprout!

2008 will be a similar year of recovery so will take heed of the lists and add even more to the garden to continue to bring in the bumblebees and their friends, and I might as well plant something for the groundhog since he appears to be staying for the long haul!

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Posted by woodsyearthmama (from Lynchburg, VA) on April 28, 2008 at 10:32 AM:

Just moved from sandy loam to Virginia clay...been plugging away making compost and such! Thanks for the wisdom...

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Posted by soive2000 (from Austin, TX) on April 28, 2008 at 9:04 AM:

As I live in Austin Texas area I had a profound interest in your article.
I recently moved into a new house and have been reading and re-reading about plants that grow well in not only clay dirt, but also alkaline laden dirt.
I have been working a lot with using native plants of Texas and am trying to incorporate xerascaping(sp) techniques in my yard. The suggestion about using a hand cultivator really made me think and I will use it next time I plant a new plant.
I have dug out the entire front yard of my yard, yes I hand tilled it, and have many more plants I want to plant.
Thank you for writing.
Have a great day,
Anita

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Posted by pelletory (from Marlton, NJ) on April 28, 2008 at 8:20 AM:

Clay definitely is a challenge!

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Posted by davis1676 (from Disputanta, VA) on April 28, 2008 at 8:55 AM:

I want to chime in & agree with pelletory. However after reading this article, I'm feeling a bit optomistic. Think I will pursue the idea of working with what I have & trying to take advantage of it. Maybe instead of my constant complaints about the clay, I can embrace it's attributes. Thanks for giving me a bit more positive perspective. Great article!

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Posted by savagegardener (from Middleton, TN) on April 28, 2008 at 9:10 AM:

and I would add ... use Gypsum, it will indeed break up the clay particles over time... it is working in my hard red clay soil!!
Sharon

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Posted by Pamgarden (from Nellysford, VA) on April 28, 2008 at 9:45 AM:

I am learning to love my clay soil, amending in the lasagne method, with layers of shredded paper, wood chips, leaf mould, compost, alfafa meal, green sand, and kitchen scraps.

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Posted by Brent_In_NoVa (from Sterling, VA) on April 28, 2008 at 10:12 AM:

Yes, thanks for the article. It seems that the one thing that gardeners all have in common is that we like to complain about our soil! I deal with heavy red clay soil in Virginia. I have had more than one neighbor complain that nothing will grow in this soil and comment about how lucky I am to have nice soil in my yard. Luck? The three tricks that I have found for working with clay soil are organic matter, organic matter and organic matter. Compost...shredded leaves...organic mulch...lasagna gardening...it all helps.

As pointed out in the article...it makes much more sense to work with your soil than fight it. About the fastest $24 that I wasted was some lavender plants that I killed. I figured that if lavender does not like my rich, moisture retaining soil then that gives me more room for one of the other 1000 plants that do like those conditions.

- Brent

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Posted by KaylyRed (from Watertown, WI) on April 28, 2008 at 10:39 AM:

What a great article, Toni!

I've learned to make peace with our clay soil. Bit by bit I'm getting it amended with compost. It's improving slowly but surely. A good top dressing worked into the soil each year seems to be working well for me, as well as compost in new planting holes, as you mentioned.

This is important with any soil, but I find it especially important with clay, that gardeners try to avoid walking on it, particularly when it's wet. Nothing compacts like clay soil! Mine will turn into pottery wherever I step. ;)

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Posted by docgipe (from Montoursville, PA) on April 28, 2008 at 11:10 AM:

I second Brent's comments and add.....manure, manure, manure and cover crop, cover crop, cover crop.

This article is of questionable value. My first twenty years of gardening was in clay soil. Send this article back to the Land Grant College and their corporation grant providers from major chemical firms. They provided to much misery already for the folks who really trust their advisements.

Clay soil no matter how terrible can be built back to excellent structure and biological health the same way any man ruined soil can. Eliminate the chemistry and build back up the biological strengths. Just do not expect to correct in one year what took seventy five years to arrive at the condition it is in today.

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Posted by DouginMtVernon (from Alexandria, VA) on April 28, 2008 at 5:34 PM:

I agree with docgipe.

It takes time and organics, more organics, and some more organics. A hard freeze in a winter or two has definitely helped my top few inches break down more readily.

And I have to disagree with the author--when clay is heavily compacted, I don't think you can cultivate it enough, and while your doin' it you're wasting your time if you don't mix in the local supply of organic humus. That's the only way to get more living organisms and friability into that clay. It's got to be done by earthworms, earwigs, and lots of microscopic organisms. Whatever you do, DON'T dump chemicals on it that throw the living soil into imbalance. But digging only around the planting holes to me would mean that annuals and groundcovers could never get established. I say dig at least the top 4-6 inches and cultivate every year after severe compaction until they are again workable.

I've tried just this year a Cheasapeake compost made from chicken manure, crab & oyster compost, and other organic plant humus. It's primary benefit is supposed to be helping to make the clay more friable. Too early to tell, but it sure seems like the new plantings are taking to it very well.

All my beds started as immediate post-construction severely-compacted poor-draining Virginia lowland clay, and slowly every time I add more organic material I see more life in the soils, and it becomes easier and easier to work, better draining, and supporting a better diversity of plants. But if I had only dug around the planting holes a bit, I don't think my beds would be performing as well as they are now.

I now also love my clay soils, but it's been a four-year stuggle just to make them workable, and I still have a long way to go.

This message was edited Apr 28, 2008 4:44 PM

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Posted by KyWoods (from Melbourne, KY) on April 28, 2008 at 5:51 PM:

Good exercise, diggin' in the clay! A little too much exercise, every time I hit a rock, though...
Yep, I read that the clay is rich in good minerals for our plants, so instead of just throwing it all out, I do mix it with the nice forest topsoil (leaf mold) that we thankfully have so much of here.
Oh, and the rocks that are diggable make nice rock walls for more flowerbeds!

Thanks for the informative article, since there are so many of us with this issue.

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Posted by docgipe (from Montoursville, PA) on April 28, 2008 at 6:05 PM:

The clay we speak of is usually related to limestone. Both were at the bottom of the oceans before being faulted up to where they are found today. If your home is on clay soil that soil was one day the floor of the ocean.

What is scary is that most all the non-biodegradable chemicals absoutely end up back there in the pits and canyons of the ocean floor. The poisoned pits and areas in the oceans of the world that are absolutely known. That is not to hard to figure out. How to effectively stop the flow from my backyard and other major sources to the oceans of the world is not such an easy project and yet remains or should remain everyone's concern.

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Posted by Liquorice (from Melbourne
(Australia)) on April 28, 2008 at 6:56 PM:

I agree entirely with those who advocate massive amounts of organic material for improving clay soil. Clay is definitely a great store house of nutrients for plants, all we have to do is give them access to them. Here in Australia, not only are many of our soils clay, it is very old and tired soil from way before man added his bit. We also have major watering restrictions which adds an extra challenge.

When I work clay I start with a six foot crowbar, breaking it up the surface as much as possible. The use of a rotary hoe produces a hard barrier below the cultivated area and a fork does not penitrate deep enough. I then add as much organic material, (leaf mulch, compost, animal manure, etc) as I can find, going as high as 12 inches or more, and leave the hard work of cultivation to my thousands of helpers (worms) for a few months. This takes care of the top of the garden. Up to three inches of a good organic mulch are added each year. It is important to use a mulch that breaks down easily.

When planting trees I dig a coned shaped hole. This guides the tree root down to a point which they will push down through. Digging a hole with a flat bottom, no matter how large, forms a hard surface that deflects the roots back.

And under no circumstances use any form of chemicals in the process as you will undo all of the goodness of the humus you have created.

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Posted by greatswede (from Lincoln, CA) on April 28, 2008 at 8:25 PM:

Is anyone here familiar with a product called "Liquid Gypsum" put out by Soil Logic Pro and EZ-Flo? EZ-Flo sells a liquid fertilizing system that is injected into the irrigation system.

They claim that it has the "ability to displace sodium cations and replace them with calcium cations, and then create a positionally stable aggregate structure all in one operation."

[HYPERLINK@www.ezfloinjection.com] is the web site that describes this product in detail.

I've been using this product for the past two months and I believe I can see an improvement. One example are my Vinca minors. Up until now they looked like squashed cabbage leaves. Now they are look like they have come alive. Our soil here in Lincoln, CA is really bad. Heavy clay with rocks and has very poor drainage. It's been hard to find anything that would grow in our hot sun, poor drainage and survive frosts in the winter. Even Oleanders have a rough time here.

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Posted by laura10801 (from Fairfield County, CT) on April 29, 2008 at 11:10 AM:

I have clay soil and hated gardening until I discovered the pick-axe. I couldn't break through the soil without it. Now I'm an avid gardener and I'm always looking for ways to live with and make my clay soil work for me. I don't often try to amend it because it is way too hard for me and doesn't seem to work very well.

I found this article and this thread helpful and I have bookmarked them both.

Thanks a lot.

This message was edited Apr 30, 2008 12:11 PM

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Posted by DouginMtVernon (from Alexandria, VA) on April 30, 2008 at 2:25 PM:

More food for thought on this author's recommendations.

In my area, the following recommended plants either are documented alien (non-native) invasives, or are borderline invasive:

Miscanthus/Grass (Miscanthus sinesis)--plenty of suitable native substitutes available--certain native Panicums but some of them can be invasive also.

Butterfly Bush (Buddleia davidii)

Nearly Wild Rose (Rosa rugosa)

Burning Bush (Euonymus alatus)

Japanese Barberry (Berberis thunbergii)

Spirea (Spiraea spp.)

AND ESPECIALLY
Bradford flowering pear (Pyrus calleryana 'Bradford') ---This tree has been naturalizing in Virginia at an alarming rate, crowding out such natives as Redbud, Dogwood, and other eastern flowering favorites. It tends to obstruct native opportunistic plants from establishing populations. I hate it. Can you tell?

Some people's invasives are others' delight. But unfortunately, wild native populations are suffering at an excelerating rate, and it is up to home gardeners to plant responsibly and not contribute to an already dire situation (in some areas including mine).

Like I said, just some food for thought.

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