Overseeding Established Old Lawn


Hi and thank you for this resource and helping home owners.
I have 3/4th of my backyard with established thin lawn and 1/4 badly weedy and bare patches. I have seeded and applied starter fertilizer and by July mid it would be 6 weeks. I see a little sprout of grass in some areas. It is still bare and the starter fertilizer makes weed grow faster and I pull them out(misery).It will take 2 more seasons to fill up. I know the bare patches still need seeding in fall or spring and the rest of my front and back lawn need overseeding as it is a thinned out lawn. I do not want to sacrifice fertilizing as I know it’s important.
While overseeding established old lawn can I put starter fertilizer will it affect the rest of the lawn. NPK ratio?
I have lot of spores blown in from trees in spring. The last two seasons of seeding bare patches did not help as weeds outgrew the seeds.
With my need to reseed and overseed I am struggling to find a balance between seeding and fertilizing and weed killing I use good quality seed -sun and shade mix from a reputed nursery
Please advise regarding what should I do regarding seeding and fertilizing from now mid june through July end and in September. This is my third season of trying to correct the lawn.. it is slightly better but I want to do the best for my lawn.
Thanks a ton and highly appreciate this web resource.


Hello – We are glad to hear that you are finding our service helpful.  Maintaining a lush, weed free lawn is an ongoing commitment as you are discovering.  An earlier post to another gardener with lawn issues notes that fall is the best time for reseeding a lawn as there is less competition from germinating weeds and soil temperatures are warm but lawns do often need repair in the spring.  I’ve included a link to this post below as it outlines our recommended approach for over seeding.

The steps involved are:

  • Rake and de-thatch
  • Apply top soil/compost
  • Spread seed
  • Rake lightly again
  • Water well for 3 weeks till seed germinates
  • Mow – regularly at a height of 2-3 inches and leave clippings on lawn.

At this point in the season, I would continue to weed and add top soil and seed to any large patches created by the weeding. Note that the grass seed must be in contact with the soil in order to germinate which is why a second raking is recommended.  You may also want to tamp down the areas you have seeded to ensure good contact.  You can continue this practice till the summer temperatures are mostly over 80 degrees.  Follow the steps above when you over seed in the fall.  Then next year, patch as required in the spring and over seed in the fall.

The starter fertilizer you are using will not harm and may help the rest of your lawn but as you note it’s feeding the weeds too.  I don’t think a starter fertilizer is necessary.  Personally, I add no additional fertilizer to my lawn relying on the top soil/compost I put down when overseeding and the nitrogen from the grass clippings to provide nutrients for the lawn.  If you want to use a starter fertilizer, I would wait till the grass seed germinates to fertilize to give the grass seedlings a head start on the weeds.

I assume you have some shade given your grass seed is a sun/shade mix.  As grass is even more challenging to grow in shade, you might consider using your mix across the whole lawn and then adding more seed blended specifically for shade in the shady areas.  Another consideration mentioned in our earlier post is the addition of white clover when seeding. White clover germinates very quickly and helps to crowd out weeds while the grass is germinating.

Good luck.