Just like all other plants, grass needs nutrients, which it either draws from the soil or from fertilizer applied through a lawn care treatment. Lawn that is not fertilized will be less healthy and more vulnerable to insect invasions, disease and weeds. Fertilizers are applied in small doses several times throughout the season in keeping with a lawn’s natural growth cycle. This is called seasonal fertilization. It ensures that your lawn receives the nutrients it needs at the right time and in the right quantity, without harming the environment.