Johnsongrass and crabgrass are invasive weeds that can overtake your lawn. Crabgrass is a low-growing grass most often seen in lawns, flower beds, and vegetable gardens. While you may find Johnsongrass growing in your lawn, it will also grow in pastures, crop fields, and the edge of the road. Johnsongrass is much coarser than crabgrass. If left alone, Johnsongrass can grow up to 8 feet tall. 

The hydroseed mix—known as a slurry—helps grass seed take root in many ways. Water combines with the mulch, allowing the grass seed to stay moist while grounded in the soil. The extra fertilizer then provides the boost the seed needs to flourish. In just a few weeks, you'll be ready to break out the lawnmower again.

Very carefully. You should be cautious when using any of the above methods, as any one of them could lead to you accidentally killing desired grasses and plants. However, there are selective herbicides that can target certain plants over others. Look for a product that only affects the type of weeds you want to eliminate and spares the plants you want to keep.

Adding vinegar to your lawn increases the acidity of the area, which can kill quack grass present above the ground. However, putting vinegar in your yard will also kill the grass. Unfortunately, the below-ground quack grass rhizomes remain very much alive in the presence of vinegar and will soon sprout again.