Fertilizers are literally plant food additives. Aged soils are not always fertile enough to supply the nutrients, which healthy plants need. The soil in most areas has become so washed-out over the years that fertilizers and other additives must be added to nourish your gardens and lawn.
Click here to see how and when to fertilize your lawn.
Early spring is the time to add the hormone type weed killers, which work on the "root" of the weeds.
Why do you want to get rid of weeds when you can just mow over them? Because weeds steal plant nutrients that you are feeding the grass and compete for the root and growing space needed especially for the creeping grasses.