The best time to fight crabgrass with pre-emergent herbicide is when forsythias tend to bloom. In the mid-Atlantic region, this is usually between April and May. Even if you're late to apply the herbicide, it’s effective as long as the crabgrass plant has fewer than five leaves.

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.

If you spray a DIY vinegar solution that contains high salt, it can disrupt the soil's structure and make it difficult for plants to grow. That's why it's vital to avoid spraying vinegar solution on areas where you are trying to grow plants and flowers. When using a mix of vinegar and soap, some say you can plant a few days after the vinegar dries. 

Jet washing can wash away weeds without bending or kneeling to pull them. However, the results will likely be fleeting because the weeds will return unless you use a stronger method that takes them out at the root. Use a jet washer for short-term weed removal, but use a stronger method if you want to get rid of weeds for good.