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How to Improve Clay Soil and Poor Garden Drainage

Updated on December 7, 2013
clay soil easily form a ball in your hand
clay soil easily form a ball in your hand | Source

Improving 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, but brick-hard in summer, but with care you can improve the structure rapidly.

All clay soils become easier to work with if you add organic material.

Garden compost is best, but soil conditioners such as seaweed, farmyard manure or bagged manure products such as Scott's Organic Dehydrated Manure are also available and will help improve the quality of the soil.

Spread the soil conditioner over the soil, and use a garden fork to turn it in.

This is probably easiest to do in spring autumn after the rains, as clay soil is easier to work with at this time of the year.

Use about a barrow-load of compost or manure to 3 m2 (3 sq.yds) and spread to a 8cm (3") thickness.

Dried seaweed meal also improved the structure of the soil.

Apply 100 - 200 g per m2 (3 - 6 oz per sq. yd).

Follow the instructions carefully when applying proprietary products as they can do more harm than good if applied too thickly.

forking organic material into clay soil to improve it
forking organic material into clay soil to improve it | Source

As someone who has worked with clay soils for many years, on many different locations, I can say that clay soils are improved rapidly when using the technique outlined above.

The soil, within a year or two, becomes much more friable and easy to work with, but it does take many years of repeated applications to reverse the soil structure completely.

Soil constantly encroaches from surrounding areas every time it rains, and dilutes all your efforts.

However, it is well worth making the effort to improve your clay soil structure, as with the passage of time, it becomes much easier to work with.

pH of clay soils

Clay soils tend to be acidic, but not always. In my current garden the soil is not only clay, it is extremely alkaline.

The simple way to find out the pH of your soil, is to buy a soil pH kit.

They are very easy to use and can tell you in just a couple of minutes whether your garden soil is acid or alkaline.

While it is possible to adjust the pH of your soil in order to grow certain plants, you will find this a time-consuming and expensive business.

While adding in compost and organic material is always beneficial, and does tend to help neutralise 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 useful.

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.

flowering garden built on clay soil
flowering garden built on clay soil | Source

Choosing the right flowering plants for clay soil

If you choose your plants with care, a garden on clay soil can flourish. The selection below all flower at different times of the year, giving your garden a splash of color all year round.

Plants that do well on clay soils

  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 A. 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 will not thrive on clay soils

  • Bulbs - avoid the smaller, delicate ones which need light, warm soils.
  • Alpine species which are usually grown in rockeries.
  • Lilies, except the Madonna lily Liliium candidum and L.pyrenaicum. Lilium regale could also be grown if the soil is cultivated and well-drained.
  • Rock roses (helianthemum spp)
  • Sea hollies (Eryngium maritimum) and other eryngiums which grow naturally in sandy soils.
  • Irises - especially the smaller ones. But Iris foetidissima grows well on clay.

Organic Manure to Improve Clay Soils at Amazon

Clay soil drainage

Clay soils tend to becme waterlogged during wet weather, as the grains tend to stick together and does not let water drain away easily.

Not only do most plants, except bog plants, not like having their feet wet and will quickly rot, it can spoil your own use of the garden.

If you have an area of garden under lawn, you will quickly see damage and moss formations, not to mention the difficulties of traversing waterlogged ground should you dry your clothes outside on the line, for example.

You can help by aerating the ground by making drainage holes with a garden fork or similar tool, but if the problem persists, you may want to consider installing land drainage pipes to remove excess water permanently.

drainage problems to due to heavy clay soil
drainage problems to due to heavy clay soil | Source
herring bone layout of drainage pipes
herring bone layout of drainage pipes | Source

Land drainage for clay soils

This involves opening up a series of deep trenches across your garden, on areas where you might walk.

You will wish to have a main drainage ditch, about 2 to 3 feet deep in a straight line, in an angle across your garden with a downward slope.

In a herring bone fashion, you will need to dig other trenches the feed into the main trench.

In each trench you lay piping and interconnect them. Buy special drainage plastic tubing with drainage holes across the top to collect the water. Set them down on a bed of stone chippings inside the trench, and angle them so that any water collected will always flow into the main pipe.

Finally you build a soakaway, which is a deep circular hole with sloping sides. You will want your soakaway to be at least 6 feet deep. Position it well away from the house.

Your main drainage pipe should feed directly into the soakaway which you infill with rubble to allow water to collect.

Cover your soakaway with thick plastic sheeting.

In areas of poor rainfall, you may want to build a concrete soakaway to retain water to sustain your gardenin drier times.

laying herringbone garden drainage in heavy clay soils
laying herringbone garden drainage in heavy clay soils | Source

French drains for water drainage

French drains are basically just the same as above but without the pipes.

Instead you infill the trenches with rubble and gravel before replace the topsoil.

The idea is that heavy rain will drain away off the surface of your clay soil, which makes walking on it in wet weather more pleasant as it will be drier.

A major difference between the two land drain systems is that when you dig your trenches for pipes, it does not matter if the floor of the trenches do not drop away to the water outlet, as you can adjust the fall with gravel.

With French drains, you must measure exactly the fall of the land to 1:100 as that is the correct level to allow water to drain away.

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


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    • IzzyM profile image

      IzzyM 5 years ago from UK

      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.

    • PegCole17 profile image

      Peg Cole 5 years ago from Dallas, Texas

      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 profile image

      IzzyM 5 years ago from UK

      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 profile image

      Dolores Monet 5 years ago from East Coast, United States

      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 profile image

      IzzyM 5 years ago from UK

      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 profile image

      Writer Fox 5 years ago from the wadi near the little river

      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 profile image

      Kris Heeter 5 years ago from Indiana

      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 profile image

      IzzyM 5 years ago from UK

      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.

    • Sue Adams profile image

      Juliette Kando 5 years ago from Andalusia

      Thanks Lizzy, you are motivating me.

    • writer20 profile image

      Joyce Haragsim 5 years ago from Southern Nevada

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

    • IzzyM profile image

      IzzyM 5 years ago from UK

      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.

    • writer20 profile image

      Joyce Haragsim 5 years ago from Southern Nevada

      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 profile image

      IzzyM 5 years ago from UK

      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.

    • Sue Adams profile image

      Juliette Kando 5 years ago from Andalusia

      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 profile image

      IzzyM 5 years ago from UK

      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.

    • Sue Adams profile image

      Juliette Kando 5 years ago from Andalusia

      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.