Container Garden Secrets of the Soil

I found this article very helpful in identifying the different types of soil to use in my container gardens. I think you’ll enjoy it, too.

You will probably hear gardeners talking about sandy soil or clay soil when deciding what sort of soil your plants will do best in. Have you ever wondered why there are so many different soils and what is the difference? Although it can sound quite complicated, it is rather simple and once you understand the basics, you can make and alter the soil for your containers to suit the plants you are growing. It is just like following the recipe for a cake mix but easier, you do not have to cook it!

All soil is made up of broken up rocks and decaying animal and vegetable matter, called humus or compost. Over millions of years the surface rock of the planet has crumbled and become worn down due to the actions of wind, water, heat and cold. Most of this hard rock has worn down to form sand.


The sea beds under our seas and seashores around our coasts are great masses of pure sand. If our soil was just sand it would be very unproductive, just think of the large deserts where hardly anything grows. It is thanks to the millions of life forms both big and very small that die and decay over the years, that the soil becomes rich in food that enable plants to grow and flourish.

So, when we speak of sandy soil, we are talking more of the sand as a sort of filler, mixed with the humus or compost of decaying matter which often includes animal waste as well. This is why gardeners prize well rotted horse manure so much and dig it in to their soil, to enrich it. The sand helps to stop the soil become compacted and allows air and water to flow through the soil, which is needed by the plants and the myriad of small insects and micro-organisms that call it home.


These are small particles of worn down quartz and feldspar rocks that are bigger than sand but heavier than clay in water. Think of rock dust.


Another type of worn down stone, is found in lime soil. This soil is formed from worn down particles of limestone, which in turn is made up of the skeletons, shells and houses, like those of snails and crabs, that have lived and died over millions of years. These creatures picked lime particles from the water they lived in to form their shells as protection from larger creatures. You can still see this happening in coral reefs. When they die, their hard skeletons remain in layers on the river and sea beds and then over time these great masses of shells have been crushed and pressed by geological events to give us limestone.

Some of the old shells can still be seen in the limestone. Marble is another crystalline form of this special sort of rock, as is chalk. A way to test if a rock is limestone is to drop on it a little acid, such as household vinegar. This will react with the lime and cause it to bubble. This is why it can be used to balance soil that is to acidic


Now when a rock is worn by the elements, this is called “mechanical” action but there is another type of soil called clay. This is formed when a heated rock is attacked by a natural gas called carbonic acid, a form of carbon dioxide that all living things breathe out. This is not a mechanical action or wearing away of the rock but a chemical action where the rock is eaten away. Sand and silt are just a large rocks worn down into smaller pieces, like breaking up a sugar cube. It remains the same stuff it started out as but has just becomes smaller. Clay is the result of a chemical change, you start off with one sort of rock, but end up with something different. Clay soils are sometimes also refereed to as mud soils because of the water they contain. Compacted clay becomes waterproof and was used to line village ponds.


Peat is not rock based but is a form of compost or humus. It forms in marshy areas where the rotting plant material is slowed down from rotting fully by the acidic conditions. Have you ever seen the contents of a compost bin that gets to wet? When you have to add paper or straw to balance it? The peat bogs grow very slowly at the rate of about a millimetre per year. Some of the peat that is sold in garden centre has taken 9000 years, from the last Ice age, to form. This is why many people are campaigning for the peat bogs preservation and asking gardeners and farmers to use peat substitutes. This tends to be acidic and is added to the mix for those acid loving plants or to neutralise soil that has to much limestone.


Lastly and most importantly we have Loam. Loamy soil is a mixture of the other soils that is regarded as the best sort of soil for growing in. It is roughly in the proportion of 2 of sand to 2 of silt to 1 of clay, with lots of natural humus. Loams feel gritty, moist, and retain water easily and allow air circulation when not compacted. This is the holy grail of gardening and if this occurs naturally in your garden you are blessed. Within reason, the more organic matter you can add to it the better it will be.

The search for excellence

Fortunately, now that you know the basic secrets of the soil you can alter and mix these different components to make the right balance for you containers and planters to suit the needs of your plants. By mixing sand/silt with clay and adding compost from your compost bin or from your wormery and then balancing it with limestone or using peat (or peat substitute) to make it slightly acid. This is why I said it is just like mixing a cake recipe, and many gardeners do in fact have their favourite recipes for making “soil”.

The old cottage gardeners would judge the finished mixed soil or loam, by its wetness and its rich dark colour. When you squeeze a handful of loam, the soil will tend to stick together but not be strongly bonded. When you open your hand you will see that it is slightly stained. Then you know you have the perfect growing medium for your containers.

To find out more about the secrets of container gardening and “recipes for mixing your own soil visit Container Garden Secrets and download your free ebook. Greenjackdavey is an Artist and Gardener living in South West England.

Article Source:  Container Garden Secrets of the Soil

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