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How to Improve Clay Soil and Poor Garden Drainage

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Having worked with clay soils for years, I've learned a few simple ways to improve the structure of the soil.

This article provides tips and tricks for how to improve clay soil structure and clay soil drainage.

This article provides tips and tricks for how to improve clay soil structure and clay soil drainage.

How to Improve the Structure of Clay Soil

If you can roll a handful of your garden soil into a sticky ball, it is clay. Clay soils are sticky in winter and brick-hard in summer. With the following tips, you can improve the soil rapidly. However, it may take several months to a few years to completely change the structure of heavily impacted soil.

Add Organic Material

All clay soils become easier to work with if you add organic material. I've found that garden compost is best, but conditioners such as seaweed, farmyard manure, or bagged manure products like Scott's Organic Dehydrated Manure can also improve the soil quality.

This process is easiest to do after the rains during spring and autumn, when clay soil is easier to work with.

  1. Spread the soil conditioner across the surface and use a garden fork to mix it in.
  2. If using manure, spread to an 8 cm (3") thickness.
  3. If using dried seaweed meal, apply 100–200 grams per square meter. (3–6 oz per square yard).
  4. If using proprietary compost mixtures, follow the instructions on the package carefully. Improper use can do more harm than good.

After a year or two of repeated applications, the soil will become more friable and easier to work with.

Forking organic material into clay soil to improve it.

Forking organic material into clay soil to improve it.

What Is the pH of Clay Soils?

Clay soils tend to be acidic, but not always. Although my current garden soil is clay, it is alkaline. A simple way to find the pH of your soil is with a pH kit. They are very easy to use, and you can find out whether your garden soil is acid or alkaline in just a couple of minutes.

Can I Change My Soil pH?

While it is possible to adjust the pH of your soil to grow certain plants, the process can be time-consuming and very expensive. Adding compost and other organic materials tends to neutralize the soil, so you'll have trouble growing plants that love either acidic soil or alkaline soil. This is where raised bed gardens are useful.

While adding in compost and organic material is always beneficial and does tend to help neutralize the soil, you are still going to have trouble growing acid-loving plants in alkaline soil, or alkaline-loving plants in acid soil, and this is where raised bed gardens come in handy.

Whether you choose to buy a ready-built raised bed garden or have one constructed from wood or brick, you can choose to fill it with a compost of your choice, and grow your plants of choice.

Improve the texture of your heavy clay garden soil, but make a point of growing flowers and vegetables best suited to the natural pH of your soil.

Raised bed gardens allow you isolate your plants from the ground soil.

Raised bed gardens allow you isolate your plants from the ground soil.

Are There Plants That Can Grow in Clay?

There are certain plants that can grow in clay soils. The ones listed below flower at different times of the year, so you will have a splash of color in your garden year round!

Flowering garden built on clay soil.

Flowering garden built on clay soil.

Plants That Can Grow in Clay

  1. Flowing currants (Ribes sanguineum)
  2. Hardy geraniums (Geranium sanguineum, G. pratense, G. macrorrhizum, G. enderssii)
  3. Hellebores (Helleborus atrorubens)
  4. Ivies (Hedera spp)
  5. Japanese anemomes (cultivars of Anenome hupehensis or Anenome x hybrida)
  6. Lungworts (Pulmonaria saccharata)
  7. Paeonies
  8. Roses
  9. Snake's head fritillaries (Fritillaria meleagris)
  10. Snowdrops (Galanthus nivalis)
  11. Winter aconites (Eranthis hyemalis)

Plants That Cannot Grow in Clay

  1. Bulbs: Avoid the smaller, delicate ones that need light, warm soils.
  2. Alpine species that are usually grown in rockeries.
  3. Lilies, except the Madonna lily (Lilium candidum and L.pyrenaicum). Lilium regale can also be grown if it is cultivated and well-drained.
  4. Rock roses (Helianthemum).
  5. Sea hollies (Eryngium maritimum) and other Eryngiums that naturally grow in sandy soils.
  6. Irises, especially the smaller ones. However, Iris foetidissima can grow well in clay.
Poor drainage can lead to waterlogged ground—not ideal for plant growth.

Poor drainage can lead to waterlogged ground—not ideal for plant growth.

How to Drain Clay Soils

Clay soils tend to become waterlogged in wet weather; the grains tend to stick together, preventing water from escaping. Most plants, except bog plants, do not like having their feet wet because they can quickly rot. You may also find that it's hard to walk on the waterlogged soil.

A quick fix is to make drainage holes with a garden fork or similar tool. However, if the problem persists, consider installing land drainage pipes to remove excess water permanently.

Herringbone drainage system. The main drainage pipe (middle) drains downward, away from the house, toward the soakaway (SA).

Herringbone drainage system. The main drainage pipe (middle) drains downward, away from the house, toward the soakaway (SA).

Creating a Herringbone Drainage System

This involves digging series of deep trenches across your garden, in areas where you might walk.

  1. Start by digging the main drainage trench—two to three feet deep in a straight line across your garden. Be mindful of the slopes of your garden when positioning the trench. You want to have the trench at a downward slope.
  2. Dig trenches that will feed into the main trench in a herringbone fashion.
  3. Cover the surface of the trenches with gravel or small stones.
  4. Lay piping in each trench and interconnect them. Use special drainage piping with drainage holes across the top to collect the water.
  5. Angle the pipes so that water will flow into the main pipe.
  6. Build a soakaway—a deep circular hole with sloping sides—at the end of the main pipe. The soakaway should be at least 6 feet deep and filled with rubble to collect the water.
  7. Position it well away from the house.
  8. Cover your soakaway with thick plastic sheeting.
  9. In areas of poor rainfall, you may want to build a concrete soakaway to store water for gardening during drier times.

Alternative: French Drainage System

An alternative method is to create french drains. French drains are like herringbone drains without the pipes. Instead, the trenches are filled with rubble and gravel and replace the topsoil.

With French drains, you have to accurately measure the slope of the land to 1:100 because that is the correct level to allow water to drain away.

Clay soil can be a nuisance, but the addition of organic matter, and where flooding is a serious problem, the addition of land drainage can make your clay soil garden easy to maintain and enjoyable to use.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.


IzzyM (author) from UK on December 10, 2011:

It's horrible stuff to work with, isn't it? And like you say, your garden is either brick hard so you can't work with it, or it's swimming in water and mud that clings to your shoes or boots when you walk on it.

Peg Cole from North Dallas, Texas on December 10, 2011:

That picture of the garden looks just like mine did. We have clay soil here in Texas and with the severe drought we're under, the yard has turned into giant bricks. When we were having the 100 year floods a few years back it was just a clay soup farm.

IzzyM (author) from UK on December 09, 2011:

I installed my own land drainage system years ago when I was young and fit, and that included digging out the trenches. It was a LOT of work, but it worked. If you employ a company to do it for, beware of workmen trying to charge a fortune - they'll bring in a machine and have it dug out in half a day or something and want to charge you big bucks. It's many better for you to hire the machinery and employ someone with a bit of muscle to help you. Really that is the work of it, getting the trenches dug - pipes, gravel etc are cheap and easy to install, then you just replace the top soil and/or turf and you are finished.

Dolores Monet from East Coast, United States on December 09, 2011:

When I dig around in my garden, sometimes I forget how awful it was when we moved in. Then, if I start a new garden, or go to plant something in unimproved soil, I get the surprise of feeling like I am trying to dig in cement. Plus, we have the drainage problem in the grassy part of the yard. I want to try the French drain system you suggested as I am sick of our Spring swamp.

IzzyM (author) from UK on December 08, 2011:

Earthworms can't live in heavy clay soil that is mostly dry like here. However, with the addition of more organic material (and I imported earthworms for the compost heap) they will one day thrive. I hope. @kris, well done I am glad to hear your soil is improving!

Writer Fox from the wadi near the little river on December 08, 2011:

This is an excellent article! I think it should be Hub of the Day!

PS: earthworms and kitchen scraps can help clay soil, too.

Kris Heeter from Indiana on December 08, 2011:

We have lots of clay here in Indiana too. These are very useful tips - I really could have used these tips 15 years ago when I started planting gardens and had no clue what was doing :) Over time, I've worked more organic matter in so it's not as bad anymore - it definitely takes time and hard work!

IzzyM (author) from UK on December 07, 2011:

Apart from the whole clay soil aspect, I like the idea of isolating and growing plants that would normally struggle in this climate, like potatoes. I have had no success with them here, and the shop-bought ones are horrible. I'm hoping to raise some Ayrshires, in the winter, in a raised bed garden.

Juliette Kando FI Chor from Andalusia, southern Spain on December 07, 2011:

Thanks Lizzy, you are motivating me.

Joyce Haragsim from Southern Nevada on December 07, 2011:

Thanks, maybe I will get outside and do what you've suggested.

IzzyM (author) from UK on December 07, 2011:

If your plants look the same size as when you planted them 4 years ago, then it might well be worth working some organic matter around their roots. Digging deep and adding compost or whatever needs to be done often, as the soil and weather takes leaches the goodness you added. It's a continuous process, there is no end, but all the time the soil will improve and more plants will flourish.

Joyce Haragsim from Southern Nevada on December 07, 2011:

We have clay soil here in Nevada. When we moved in I had dig deep then put some nature soil in the bottom and around the plants before closing them up. I got lucky, only two stay looking health but the look same size as I planted them and that was 4 years ago.

Great hub to help us, thank you.

IzzyM (author) from UK on December 07, 2011:

It'll be fine in a raised bed garden even if there are eucalyptus nearby because they won't share the same soil. I have not actually heard of a connection between eucalyptus trees and veggies? Make sure you don't put ordinary garden soil in your raised bed, else you're just raising the level of your garden. If you can afford to buy either topsoil or the cheap compost your local garden centre sells, fill it with that instead. Else do like I am doing, and make your own. I am slowly filling the new raised beds with grass cuttings and kitchen waste, but am thinking of asking the neighbours for their left-overs too because it will take forever. When it is finally ready, it should more or less pH neutral which will be great for growing just about anything. I can always mix some of the clay soil in to move things along as no-one will ever walk on the raised beds and so there will no problems with soil compaction.

Juliette Kando FI Chor from Andalusia, southern Spain on December 07, 2011:

Right, I planted lots of oleander and fruit trees. The 5 year old eucalyptus trees are now 20 meters high. Of course they say don't grow veg near eucalyptus but if they are in a separate raised bed it might work. What do you think?

IzzyM (author) from UK on December 07, 2011:

Well Sue you are just down the road from me, and I built raised beds this summer - it finally got to me!! Also with raised beds you can water what needs watering and know it is not going to waste. Then just plant the usual Spanish desert plants in the garden like oleander, and palm trees and stuff. Those plants just don't seem to care about clay soils.

Juliette Kando FI Chor from Andalusia, southern Spain on December 07, 2011:

Thank you for these useful tips Lizzy. My clay soil in southern Spain has been driving me barmy. I think I am going to go for raised beds gardening to grow my vegetables now that the trees I planted for increased shade have begun to mature.