There are tools known as “sprinkler donuts” that are specially designed to aid in cutting the grass around your sprinkler heads by protecting them from your mower or weed whacker. You can also use a pair of hand shears to do the job manually if you’re willing to get a little dirty.

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.

Water the lawn thoroughly, apply fertilizer, and overseed if necessary to promote healthy growth.

It usually takes between two weeks and a month for weeds to fully die off after you spray them with herbicide, but they will start to wilt within the first week. Different weed sprays produce different results, with some working more quickly and effectively than others. Similarly, some weeds are killed more easily than others. Consult your weed removal pro for an exact timeline based on their weed removal method.