I don't have a heavy layer of dead grass and my lawn is not very built
up so is it necessary to get the new seeds to grow? I read that you
need to dethatch only if the dead material is over 1/2". Mine is much
less.

Joe wrote:
I don't have a heavy layer of dead grass and my lawn is not very built
up so is it necessary to get the new seeds to grow? I read that you
need to dethatch only if the dead material is over 1/2". Mine is much
less.

For grass seed to germinate it must be in contact with the soil, so
when over seeding you need to dethatch or your germimation rate will
be extremely low... much better if you aerate too. When the seed sits
atop the thatch (regardless how little thatch) not only won't it
germinate but the birds will eat most of your labors the very first
day. Even when doing a superb job and followintg all the directions
the birds will still devour a substantial amount of your seed...
that's why it's called OVER seeding, as in an OVER abundance of seed,
much more than would be necessary if there were no birds. Birds are
attracted to grass seed like a magnet, that's why when many people put
in a new seeded lawn the last thing they do is cover everything with a
few inches thick blanket of straw to deter the birds.