Aerating and Seeding
Aerating and Overseeding is a very popular and easy way to renovate an old tired worn out lawn. If you
have a pretty good grade on your lawn now, meaning that you can mow it without hurting your back while riding
your mower or without scalping the top off of high spots, then aerating and over seeding is the method for you.
Quick and easy and most anyone can do this seeding method themselves.
First you will need an aerator. The coring type is best, don't use a spike type aerator, they just press the soil
down and out to the sides making a hole. It actually makes compaction worse, the core aerator will pull a plug
or core out of the ground and deposit it on top of the ground leaving a hole in the ground about 1/2" by 2 or 3"
deep. These cores help to loosen the soil so it is beneficial to aerate a lawn by itself, even without seeding.
The more traffic a lawn gets the more it needs aerating. Soccer fields, football fields and other high traffic fields
will get aerated several times per year, just to relieve the compaction.
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Topdressing a field or lawn at this time is helpful too. Topdressing is spreading
a thin layer of sand, compost or other organic material over the lawn after you
aerate, followed by dragging a drag of some type over the lawn to pull the sand
into the holes and bust up the cores left behind by the aerator.
For most home lawns, you can aerate once a year, fall is best, and your lawn
will benefit from it. Twice a year is OK too, just don't over do it. There is a point
where your aerator is tearing out the existing grass and doing more harm than
good. For aerating and over seeding you will need to really work the ground
good though, so you will aerating more or less for what you are doing, seeding,
or just aerating.
After you have gotten the aerator, rented or bought one, mow your grass very low. Normally you don't want to scalp your lawn, but now is
the exception. We want to stunt the grass and slow down it's growth so the existing grass won't be competing with the new seedlings
too much for the first 2 or 3 weeks.
You won't be mowing the grass for that period so you don't want the grass to be 6" tall and shading out the new seedlings. After mowing
the grass close, if there is an abundance of clippings you should rake them up or to make it easier if you have a grass catcher on your
mower you could just use it to start with. You don't want the grass clippings to be piled up in places, it will choke out the grass.
Now with the lawn nice and clean run your aerator over the lawn several times. Some aerators will plug a pattern 4" X 6" some closer,
some farther. You want to aerate enough so that when your done aerating you can look down and the lawn and not see any spot that
doesn't have holes very close together. Every place there is an aerator hole, there will be new grass come up. The seeds are going to
fall into these aerator holes and germinate very fast. Grass will come up later in between the aerator holes, but the holes come first.
When your certain you have aerated enough that it looks like little plugs and holes are everywhere, your ready to seed.
Seeding Fescue or other Cool Season grasses should be done in Mar.15 - Apr.15 in Spring, or best done in Fall from Sep.15 - Oct.15.
Warm season grasses like Bermuda or Zoysia are best seeded during warmer weather, may15 - jul15, can be later but these are best
Fescue seed should be seeded at a rate of 6 to 8 # per thousand square feet. Again, you should have already measured your lawn to
know how large it is, everything you do to your lawn maintenance wise depends on how large the lawn is. This you will need to know
over and over. So if you have a 10,000 sq. ft. lawn you will need 60 to 80 # of seed. My method is to just buy in 50# increments and use
all of the bag beyond what my measurements say I need. So since I am going to need 60 - 80# of seed for this 10,000 sq. ft. lawn, I am
going to use 100#. Most of the time you can't put down too much seed. There is a point of common sense though, using 300# in this
case is a waste, the grass will just be too thick and the seedlings compete with each other and don't do as well as if you use the proper
amount. Spread the required amount of seed down using a broadcast spreader. It is best to make two passes with the seed at
opposite directions to be sure you get even coverage with no bare spots. Set your spreader on a medium setting and walk the lawn until
you cover all the lawn and use the seed up. Don't stop spreading just because you have walked the lawn over and spread seed on all of
it, use all the seed.
After you have spread the seed, spread a starter fertilizer. Starter fertilizers are called such because they help the new grass to start,
makes sense ? The name comes from the fact that starter fertilizers will have a higher middle number on the analysis like 6- 24-6 or 6-
12-12 the first number is Nitrogen, second is Phosphate, last is Potash. The last number is helpful too, the first number Nitrogen is not
needed as much during establishment, but later when your trying to push the grass to grow and get green color. The Phosphate in
starter fertilizer encourages the grass seed to germinate and get growing. After the new grass is about a month old you will need to
fertilize again with another fertilizer that has a higher Nitrogen like 15-15-15. The amount you will use is usually going to be 1 to 2 # of
nutrient you are trying to put down. In seeding we are after Phosphate so a 6-12-12 fertilizer we would divide 100 by 12 = 8.33 pounds of
fertilizer per thousand square feet of lawn area. 100 because we are after 0ne pound of nutrient, or 100%, the numbers on the fertilizer
bag represent what percentage of the bag is that nutrient. 6% nitrogen, 12% phosphate, and 12% Potash. Now for our 10,000 sq. ft.
lawn, we will need 8.33 X 10 or 83 pounds of fertilizer, again just get 100# and use it all.
After the fertilizer is down take a drag of some sort and drag behind your mower to bust up all the cores left behind by the aerator, it will
also pull seed and fertilizer into the holes and cover them up with soil. Perfect conditions for germination! We use a section of chain link
fence with a board nailed to the back of it to weight it down a little. A board would work, I have even seen people use a set of bed
springs. If you have a very small lawn you can just take a leaf rake and rake over the whole lawn. This is a very important step! Dragging
the lawn will increase your germination rate a great deal. Dragging the seed into the holes and busting up the plugs will cover the seed
which is one of the three primary things you must have for seed germination. Seed to soil contact, Moisture, and the correct
temperatures for your seed type, is what is required for seed germination. Cool season grasses will need around 3 consecutive days of
soil temps in the 55 degree range to germinate. Warm season grasses will require around 85 degrees soil temps for a week or more.
If you have any spots that are completely bare from no grass or you aerated them until you made it just dirt, spread some straw on
these spots. You don't have to spread straw on the areas where there is still grass, the grass will do the same thing the straw does
which is retain moisture and keep the seed from washing away.
Warm Season Grasses
Aerating and seeding warm season grasses is just the same as seeding cool season grass only the time of year is different. They are
called warm season grasses because they grow best during the warmest time of the year. In our area of Tennessee, being Paris, Tn.
we seed Bermuda from May until Jul. This is optimum timing, doesn't mean you can't do it in Aug. it just means the earlier you get the
seed in the ground the faster the grass can develop a root system.
The key to survival is a deep root system, the deeper the roots the better it will survive a dry period. The summer of 07 in our area was
the driest, worst summer on record back 120 years, people in southern Tennessee and Alabama, Georgia even had it worse. So there
is a lot of reseeding going on around here now. Follow all the directions above for seeding Cool season grasses if your doing Warm
Season and your results will be the same.
The last thing on your Aerating and overseeding list is to water, water, water, and water some more. Just as soon as you get done
with your spreading straw and seed, fertilizer, etc. get out the sprinklers and start watering. Remember that seed will not germinate if it
doesn't get wet and stay wet.
Water the first time until the ground is muddy, water puddled up, etc. After this initial watering you will need to water as much as it takes
to keep the ground moist. It doesn't have to stay muddy, just wet. If it is hot and dry outside you will need to water every day, if it is fall and
cloudy and raining every few days you may not need to water at all, use common sense and keep the ground wet. No water, no grass!
By now you have spent a lot of money and time on this project, the results of it will be determined by how much you keep it watered.
Water until the grass is around 3" tall, at this time you will mow it for the first time. Stop watering for a day or so to let the grass dry out,
and mow the grass with a sharp blade, set your mower up high, 3 or 4". All you want to do is cut the top off of the existing grass to cut it
down and let some more light in on the new grass which will only be about 1 or 2" tall. DON"T cut the grass below 3", you will pull up
and kill the new seedlings. After you have mowed, go back to watering for another week or so until the grass has completely filled in.
Then set up a watering schedule for Maintenance instead of Establishing grass. Refer to our page on Irrigation for more watering
instructions. Watering Instructions