Garden centers and hardware, home improvement, and retail stores sell a variety of grass seed and seed blends for home lawns. It is imperative that you select only high quality "certified" seed that contains very few weed seeds and contains only the grass species you want to establish. Many low quality seed blends are available that contain a relatively high percentage of weed and weedy grass seed that may create more of a problem than you had to begin with. Beware of seed blends containing annual ryegrass, since this grass is quick to germinate and will often out compete the desirable grasses, leaving your lawn with clumps of pale green turf that is difficult to remove afterwards. Seed tags listing named varieties are usually better than tags listing varieties as "unknown". Also, only seed with a test date within the previous nine months is legal to sell.