Last September I sprayed a field to kill off the fescue,
then planted brome, orchardgrass and bluegrass. It is coming
up nicely, but I will not hay it this year. Now I wonder if
I should cut it before the seeds develop to get a thicker
root growth, or let it seed out to promote new plant growth?
I would like it as thick as possible. What do you think?
There are several things to consider beyond the growth stage
of the grasses you planted. First, if you cut the grass and
don't bale it, be sure it isn't too thick, so it doesn’t
smother itself and slow the regrowth. If you don't cut the
grass, be sure perennial weed species are not creeping into
the field to choke out the young grass. And finally, a cutting
late in the season to prevent the grass from smothering itself
through the winter may be a good idea. It sounds like you're
off to a good start.
Most of the grasses you planted like to be cut, and mowing
can actually thicken up the stand, assuming the grass isn't
too young and that it’s well-enough established. If
you planted it in September you could easily take one cutting
this year as hay without damaging the field. This depends
mostly on the weed pressure, and mowing will be the best defense
you'll have against that.
Good luck, and keep us posted on how it comes along.