How To Condition And Improve Clay Soil That Doesn't Drain Well

Filed Under: Drainage and Erosion, Landscaping, Techniques & Methods · Keywords: Condition, Improve, Clay, Soil, Poor Drainage · 1360 Views
Good Morning, it has been a while since I have posted or logged in. The last few months have been exciting moving into a new home. With a new home brings new challenges. We live in an area where we sit on a layer of limestone and above that is clay and mud. Which doesn't drain very well. I was told clay is very nutritious for plants. So the question is.....

How deep should I dig and what soil should I add to the bed. Peat moss? Cow manure? Sand? mushroom composite? Or should I just add this to the top of the clay and mud and not dig into the clay at all?

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Additional comments about this question: · Gardenality Genius · Zone 8A · 10° to 15° F
Hi Josh - Congratulations on your move and new home. If you can let us know what types of plants will you be planting in this soil and how deep the clay goes before you hit the limestone we should be able to give you some tips and suggestions for planting in it.

5 years ago ·
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Josh Hersey

Josh Hersey · Gardenality Bloom · Zone 8A · 10° to 15° F
Thanks Brent! The builder planted gardenias. I want to plant anything zone 8a and colder. I have already planted Montauk Daisies.Well, it really is hard to tell, the mixture is a grayish, white material. I hit small to large rocks about 1 foot deep. If I was to guess I would hit solid rock about 5 to 10 feet down. It isn't

5 years ago ·
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Answer #1 ·'s Answer · Hey Josh - I probably should have asked about soil pH as well, which will be important to know. While some clay soils are acid others are alkaline. Specific types of plants, such as the garenia you mentioned, require an acidic soil, while others thrive in alkaline or neutral soils. I've never tested or planted in a greyish white clay soil so not sure what pH it might typically have? Best thing to do is test the soil, or have it tested, to determine if any adjustments need to be made to pH and/or to determine if there are any nutrient deficiencies. Here's a link to an article on soil pH and how to adjust it that might be helpful...

Regarding conditioning the soil to improve drainage...specifically clay soils, it's not a good idea to use peat moss as a soil amendment. Reason being is that peat moss holds 9 times it's weight in water and clay is known to hold lots of water on its own, especially during winter and rainy seasons or periods. So, to improve drainage, you might want to add and mix in the composted cow manure or other compost and/or sand or small gravel to the soil. Mixing in some good native screened topsoil can be beneficial as well. The small rocks you found beneath the clay when digging should help to improve drainage once the heavy, muddy clay is conditioned.

Most shrubs and perennial plants should do fine (when drainage is improved) in the 12 inches of soil, but some trees might have a difficult time establishing a deeper root system that will support the tree over the long term. Worse case scenario, if drainage cannot be improved you can always build raised beds (mounds) using a good native screened topsoil. The raised mounds would ensure good drainage and keep plants from developing root rot and other diseases due to too too much soil moisture.

Hope this info was helpful and let us know if you need more details or have any other questions.


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