Half a jar of garden earth, shaken up with water and left to stand for a day, settles into bands of sand, silt and clay you can measure with a ruler. That simple reading tells you whether you garden on heavy clay, hungry sand or balanced loam, and therefore which flowers will actually thrive in your beds.
Follow our guideline one step at a time, and you’ll quickly master the art of determining the soil type for your garden.
There are 5 main types of soil:
Brown or tan in color, this type of soil is easy to shape like putty. It sticks to your fingers when wet. Although it’s very fertile, it tends to get compact and difficult to work with. It’s often qualified as heavy soil.
More grayish, yellow or whitish in color, this soil type is brittle, breaks down in hand and grains tumble out from between your fingers. Since sandy soil doesn’t retain water at all, it also doesn’t harbor any nutrients. It’s rather poor. An advantage, nonetheless, is that it’s excellent for aeration and roots can quickly dig paths through it.
Also on the brittle side, it tends to be a very light color. Chalky soil is often dry and not so fertile.
Deep black color, this soil contains extremely high levels of organic matter. It results from plant materials decomposing. It is a very fertile soil type, but is often too wet.
It’s a mix of the above. Overall the best possible soil type, with about 50 – 60% sand, 20% clay, 5 to 10% silt and 5 to 10% organic matter.
Before you measure anything, it helps to know what you are looking for. These are the five main soil types described above, side by side, with the colour and feel that give them away and what each one means for your plants.
| Soil type | Colour and feel | Fertility | Main drawback |
|---|---|---|---|
| Clay | Brown or tan, shapes like putty, sticks to wet fingers | Very fertile | Compacts easily and is difficult to work; a heavy soil |
| Sandy | Greyish, yellow or whitish, brittle, grains tumble between the fingers | Rather poor | Retains no water, so holds no nutrients |
| Chalk | Very light colour, brittle | Not so fertile | Often dry |
| Silt (humus) | Deep black, made of decomposed plant material | Very fertile | Often too wet |
| Loam | A mix of all the above | The best possible soil type | Few; the balance is what makes it good |
Once you can name your soil, choosing plants that will actually thrive in your beds becomes far simpler.
There is a simple 4-step method to nail down the right type of soil.
Dig 6 holes about 20 cm deep in different spots spread out over the garden and collect some soil. A handful is enough. After that, mix your samples all together in a pail.
large items should be removed for this analysis (rocks, sticks…). To remove them easily, use a sieve with a 8 or 10 size rating (2 to 2.5 mm or 0.07 to 0.1 inch-size holes).
Note in some cases, even after 24 hours, the water might still seem clouded. If so, you’ll have to wait for even longer, until you can see through the water perfectly.
Once the waiting is over, you’ll quickly notice the different layers that formed in your jar. The bottom-most layer is always sand. Above that, you’ll have a layer of silt. The third layer from the bottom is clay and the last layer, floating at the top of the water, is organic matter. Use a ruler to measure how thick each layer is. Sand is the easiest layer to measure since you can clearly see the grains with the naked eye. What’s most difficult is distinguishing silt from clay: both have grains that are nearly the same size. Tricks to help you out are noticing that the layer of clay at the top usually seems more compacted and uniform; it also is a different color. Once you’ve measured the layers (water doesn’t count), on to a little bit of math (note that organic matter doesn’t influence soil type since it’s not included in the computation):
Now that you’ve got the breakdown of what your soil is made of, let’s interpret the results. For that you just need a soil type triangle (also called a soil texture triangle). It’s rather easy to use:
You’ve just figured out how to determine the type of soil in your garden! It’ll be much easier to select the right kind of flowers for your flower beds.
If you’ve got a very large garden with sloped portions, you might want to prepare different sets of samples. Soil in one part might not be the same as soil further off.
