overseed

o·ver·seed

 (ō′vər-sēd′)
v. o·ver·seed·ed, o·ver·see·ing, o·ver·seeds
tr.v.
To spread grass seed on (turf or an established lawn) in order to fill in thin or bare spots.
intr.v.
To spread grass seed on turf or an established lawn.

overseed

(ˌəʊvəˈsiːd)
vb
to plant too much seed in