remove all of them. Buy some seeds and spread them. Cover the seeds with fertilizer. If you are lucky, you will see grass in 2-3weeks. It may be much cheaper.
Dig a few inches and remove all the roots of the weed. Add 2 inches topsoil. Then you can spread the grass seeds on the topsoil. If you need professional service, call 613-883-2426 for a free estimate.
