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.

Yes, Johnsongrass is a hard weed to kill. It has the ability to grow fast and spread even quicker, so it requires a detailed plan and thorough application to eliminate it. The best plan of action is to kill Johnsongrass while the weed is establishing itself by hiring a lawn care professional or following the steps above. 

Yes, weeds will grow through pea gravel but you can prevent this during the installation process. Install a weed barrier underneath pea gravel and swap it out every three years to keep weeds at bay.

Vinegar is known to be a contact herbicide, which means it kills the foliage it comes in contact with. Because of the high acetic acid concentration, horticultural vinegar kills weeds and grass more effectively. However, keep in mind that high amounts and multiple applications can affect the soil by lowering the pH levels.