Before you start any weed control program, you need to determine which of the three types of weeds you're controlling. Broadleaf weeds like creeping charlie have leaves, perennial grassy weeds like quack grass spread through roots and seeds, and annual grassy weeds like crab grass reseed themselves at the end of each growing season and germinate in the spring. Each requires unique products and application methods. Some treatments are very time sensitive, while others can be done anytime during the growing season.Plus: 6 Common Lawn Problems and How to Fix Them