Fertilizers are concentrations of elements which, when added to the soil or water, are then available for plants to use and make their own food. Fertilizers are usually naturally occurring elements such as nitrogen, phosphorous, potassium and calcium that exist in your soil. Whether they exist at the levels required for plants to grow to their potential is another matter. Over the years, gardeners and scientists have determined a rough estimate of what elements and how much of those are the best for plants and gardens. It is really the gardener's responsibility to use common sense, backed up with a bit of knowledge to make the right fertilization choices.
Fertilizers are available in a water soluble or granular form.
Water soluble fertilizers are highly concentrated particles that dissolve in water and are then immediately available for plant root uptake. These fertilizers are ideally suited to annual flowers which are particularly fond of extra nutrients. Hose-end application systems using water soluble fertilizers have made fertilizing larger beds in the outdoor garden an easy task. These would be the top three to have in your garden shed. Should you have specific challenges', there are types for acidic plants and so on.