Early Fall!
Late start in sowing seeding may ruin lawn's
chances
Dear Janet,
We are using Round-up ® to kill weeds and grass in the
back third of our lawn. How many days should we wait before laying
new dirt and planting new seed? Should the seed be protected by
straw?
C.
Dear C.,
Follow the label directions. The herbicide you used is one that
works primarily by absorption into the leaf with little or no
residual activity in the soil, so you can sow seed as soon as the
spray dries. However, you should wait for the weeds to die before
sowing. Until then, the weed foliage would keep some seeds from
making good contact with the soil and shade others. Either
condition would prevent seed germination.
Anyone who spreads grass seed hopes for quick sprouting. For you
it's especially important because it's late to sow a lawn.
Mid-August to mid-September is the ideal time to sow lawn seed in
southern Michigan, into a bed already prepared for this. The
resulting seedlings sprout by late September and grow wonderfully
in the cool fall, establishing roots that put them in great shape
by next summer. Seed sown later when it's too cool doesn't have
such a great edge since it may not sprout until spring. Late sown
seed may even be blown away or wash away over winter.
If you applied a herbicide just now you can't spread seed until
mid-October, after waiting 10- to 14 days for the weeds to die.
Then you should work the soil for sowing. This is more involved
than simply spreading new soil. Plant roots need oxygen as well as
water, but both will be in short supply in soil that consists of
loose material on top of denser stuff. I realize you may have seen
sod and seed put down on top of just such soil in countless
new-home situations but don't follow that example which is a
mistake born of ignorance and economic pressure. Those new lawns
fail or go downhill after just a few years.
Adding soil may not even be necessary. If the ground is poor,
adding compost may be a better move. That way you bring in fewer
new weed seeds and do more toward improving the soil structure and
subsequent root growth. However, you should loosen the existing
soil before adding anything, or till lightly after spreading to
combine the old and new.
You might save yourself time and have a better lawn in the long
run if you spread an annual rye seed this fall, let it sprout among
the dead weeds, then till the area in April before spreading new
perennial bluegrass seed. The rye is a "cover crop." Its roots can
improve the soil and its presence even after death can inhibit the
growth of weed seeds. By the time you till it's additional organic
matter, like compost.
It's a good idea to spread a thin layer of straw over new-sown
grass seed, provided the area is not so windy that it will simply
blow away. The straw can help shade new grass seedlings and keep
the soil cooler and more moist.
Green thumbs up
to those who keep their wits about them and seek a second
opinion in the face of outrageous advice such as "cut your maple
down if it has tar spot." I can't fathom why a competent landscape
care firm would recommend this. Unless compounded by other
problems, a disease that affects only the leaf is not
life-threatening, especially when it's something like tar spot that
comes late in the growing season. If your maple has tar spot,
relax. As bad as it looks it may need nothing but time and a change
in weather patterns to put it back into the "rarely seen leaf
disease" category.
Green thumbs down
to leaf blowers in your garden and groundcover areas. Bad enough
that you should remove the leaves that by all the principles of
soil renewal and fertility should be recycled where they fall. It's
worse to blow-dry plants already parched by weeks of drought just
when they most need every bit of water if they are going to survive
until spring. That's not all! Your perennial flowers and
groundcovers have spent the last half of the season setting buds at
and just below ground level, all for naught when those vital parts
are crushed by the blower-wielder's feet. If you can't do the best
thing and leave the leaves, use a long handled rake to remove
them.
Originally published 10/9/04