Almost half of my lawn has been overtaken with the plant that is in the pictures. Looking at it from the top, it is hard to tell these are not regular grass blades, because the green tips clump together on the surface and look like a nice green lawn. However, if you rake deeply, you'll soon discover 5-6" long pieces of this stuff, growing horizontally. Can anyone tell me what this is? I have spent hours pulling 75% of it out by hand. Can I seed over the remaining bits of it, or will this stuff eventually choke out the good grass? Can I sod over it to smother it? I'm in Toronto, so my time is quickly running out for work to be done this year. Thanks for whatever advice you can provide.