When you walk through the fertilizers, you’ll notice that bags have three numbers on them. These numbers indicate nitrogen, phosphorous, and potassium. It is the ratio of these nutrients that is important, not the number of each. A fertilizer with all equal numbers is a good overall fertilizer but you won’t get any effect from one nutrient in particular.
Nitrogen helps grow more and greener leaves. Lawn fertilizers are very high in nitrogen and flower fertilizers are low. For a new lawn, look for more balanced fertilizer so the entire grass plant is cared for and grows stronger.
Phosphorous has two major effects on plants. It helps plants bloom, which is why many vegetable and flower fertilizers have high phosphorous. It also helps plants grow strong roots, so it is more appropriate for young plants.
Potassium is great for disease resistance within the plant. Higher potassium helps plants resist not only diseases but environmental stress like temperature fluctuations or changes in watering. Potassium is good for all types of plants of all ages.
There are other nutrients that plants require that are available through several sources. The leaves are the best indicators for plant needs. Don’t forget other fertilizers like bone meal, for calcium, or blood meal, for iron. When in doubt, get a balanced, all-purpose fertilizer that will cover everything.