For healthy roots, water infrequently but water deeply, which trains roots to grow deep in the soil for strength. Deep roots help your lawn better survive a hot dry spell. By the time you see crabgrass leaves, the battle with this weed is already lost for the season. Crabgrass can only be fought with a pre-emergence herbicide before the crabgrass seeds germinate and sprout. If no forsythia bushes are in sight, call your local nursery for advice.
Dandelions are broadleaf weeds.
Wait until after they sprout and have leaves, and then hit them with a post-emergence herbicide. This weed killer is absorbed into the leaves and is circulated down into the root system. You get the best results in spring when the weeds are growing. Mow Mowing is healthy because it trims away the oldest part of the plant. Mowing also encourages a lawn to spread and thicken to choke out weeds.