Technically, dandelions aren’t bad for your lawn, and they don’t directly kill grass. In fact, they appear in areas that are nutrient-deprived, and their long taproots can loosen the soil and bring nutrients closer to the surface. 

However, dandelions do spread quickly, and they can take over your lawn, eventually crowding out grass. This is why a healthy lawn is the best defense against dandelions.

Each type of weed comes with its own control methods, but stopping the seed spread is the first step. Grazing, mowing, and hand pulling can slow the invasion. In some cases, selective herbicide is necessary to stop a persistent weed from overtaking an area.

Weeds can grow through rubber mulch, but it depends on if you removed all the weeds in your garden beforehand. Weeds already in the soil can grow even when using rubber mulch. However, that doesn’t mean that your garden will be littered with rubber and weeds, but it does mean that the occasional weed might still pop up. Another way you can increase your weed suppression is by using landscape fabric as a second layer. 

The most effective way to eliminate quack grass without killing the grass nearby is to overseed the area, keep the seed wet until it grows, mow often, and regularly fertilize the area to promote healthy grass that can choke out the invasive weed.