"Li Hao" wrote in message
...
Hi, I just bought a house last fall at San Francisco Bay area. The lawn at
backyard is full of weeds, and the size of the lawn is about 1500sq. And
only about 1/4 of the lawn has good grass.

Instead of weed killer, you might want to use a general herbicide (Roundup
etc), which will allow you to get a clean start. After a couple of
applications you shouldn't have a problem with weeds growing back. For a
lawn that size you could just use a hand spray bottle for application, which
minimizes overspray (do it on a calm day, and cover any nearby valuable
plants).

You could simply apply the seed the day after the herbicide, and rake in.
The dying plants will protect the seed while it germinates, and their
rotting roots will make room for the new grass plants in the soil. Keep well
watered of course. Get a good quality seed, appropriate to your climate,
soil and light conditions, and apply heavily.

Additionally you might rent an aerator (a machine that puts small holes in
the lawn) or get a company to do this. It will give the new grass a better
head start. And of course there's always the roto-tiller, but I'm not
convinced its necessary unless the soil is really compressed.

Finally, you could hire a company to put down one of these new seed/mulch
combinations. Some are even colored green for an instant result!