The importance of soil types in the different areas of your garden cannot be overstated, as the ph level (alkalinity versus acidity), density and moisture retention can all serve as major factors in the success of the plants you try to cultivate. Aside from this you also have the fertility of your soils to consider - while the answer of Ďricher is betterí may seem the obvious one, this can be a dire misjudgement, as some cultivars will respond too positively to high levels of fertility and end up choking the more diminutive species you host.
So, how to find out what type of soil you have?
Dominant Soil Structure
The dominant soil type is characterized by the whichever material makes up the majority of the soilís mass in your garden, be that clay, sand, chalk or silt, and these in turn can be classified by the average size of their individual particles. However measuring the tenths and hundredths of millimetres of entire beds-worth of particles would be a ludicrously painstaking exercise - instead you can test your soil texture through some simple sculpting. The home cooked test goes something like this:
Gather a small amount of soil in your palm and gradually drip water into it - youíll be able to evaluate the soilís primary type by how pliable and structurally sound it becomes once wet. You should drip just enough water to make the soil just stick to your hand. The highest density soils in ascending order are sand, loamy sand, silt loam, loam, clay loam, light clay and heavy clay, which can be defined by the different shapes they can maintain once wet. Sand based soil will barely hold shape, though it should be able to form a pyramid in your hand, whereas loamy sand will be just pliable enough to hold a spherical shape. Silt loam should form a solid cylinder though it will likely show cracks at the surface. Loam soil is classified as an equal dispersal of sand, clay and silt and will roll into a long cylinder but it will be extremely rigid, breaking easily. Clay loam will form a similar shape to loam, however, you should be able to bend this into a U shape without snapping the cylinder. Clay based soils are the most water retentive due to the amount of air between its particles and as such light clay soil will be malleable enough to make a full circle out of, however, heavy clay will do the same without showing cracks on its surface.
Acid or Alkaline?
So, that is a simple way to ascertain the structure of your soil, but another important component of your soil is the acidity. While some of the types mentioned above have a hard and fast rule on ph levels, such as sand, which is generally very acidic, and pure silt, which often contains a lot of alkaline, the best indicator you can use is a ph soil tester available at most DIY shops. Take small samples from different spots in your garden to get a true picture and follow the instructions on the pack.
However, for a do-it-yourself, basic idea of the soilís acidity you can simply pour a sample into a cup and add half a cup of vinegar. If the solution fizzes this indicates that the soil is alkaline. If nothing happens, take some fresh soil, add half a cup of water and mix. Then add half a cup of baking soda and if the solution fizzes, your soil is acidic.
Now obviously each of the soil types has its benefits and detriments, some of which you will have to manipulate in order to the house the plants you want. Sand, for example, will provide excellent drainage however this quality makes it poor at retaining minerals, while clay is rich in minerals, its density often prevents the plant from taking best advantage of them. Silt is a lighter and richer version of sand, however, its looseness makes it very susceptible to wind and water erosion and, while chalky soils provide excellent nitrogen levels, they cannot support acid inclined species because of it. The happy medium of the lot is the classic loam, both extremely rich and with an excellent consistency for most conditions. However, our previous four types can all be assisted, and even loam itself needs to be supplemented by organic matter. Organic matter will crumb clay soils and solidify sand basins, it will strengthen siltsí resistance to wind movement and, best of all, it can be free! An astute recycler can even tailor their compost to manipulate the ph level and on an even more precise level, which types of nutrients will permeate the soil. Acidic soil can also become more neutralised by adding lime or wood ash, and alkaline soils can be helped by adding pine needles, if you have some handy.
Finally, here are a few suggestions for plants suitable for each of these soils types, to get you started:
Clay-Helenium, Aster, Weigela
Sand-Cytisus, Tulipa, Lavatera
Loam-Wisteria, Erythronium, Delphinium
Chalk-Syringa, Weigela, Dianthus
Silt-Mahonia, Phormium, Nicotiana alata