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So I sprayed some weed killer and now my lawn has yellow dead spots all over. Maybe I made a mistake

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If I know it looks like this, I wouldn't even try.

So how do I fix this now?

Option A:

  • Rake off the dead grasses, put compost down

  • Few weeks later, put grass seeds over the top

Option B:

  • Just put weed and feed over it --> I expect the grasses will grow back and cover the dead ones (not sure).

Option C:

  • Basically option A but no compost, just grass seeds. Someone told me compost would burn the seeds (??!)

Thought?

UPDATE 1

I am in Pacific Northwest

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  • I have some doubts about your weed killer selection. I see broad leaves still alive, and the yellowish seems mostly mosses. What is your target? A lawn? A flowered field? If this is the first, the actual results doesn't seem promising. I would start again, before to "patch" the yellow spots.
    – Giacomo Catenazzi
    May 24, 2019 at 9:58
  • I used Roundup and spray dandelions only so others are still there. It is impossible unless I kill the whole thing and re-lawn. At this point, the majority bad are gone and leftover is acceptable enough. It is like 20% of the lawn turned yellow.
    – HP.
    May 24, 2019 at 18:06

1 Answer 1

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Option C is closest. What zone do you live in? Is this cool season grass?

The least expensive but far more intensive laborious is getting a rake, a hoe and ripping the dead stuff off of the soil. If you are familiar with line trimmers, I would scalp these yellow spots down to the ground...mow with a rotary mower to suck up debris. Bag the debris and put in your compost.

Using a rotary seed spreader spread professional (cool season grass mix zero weed seed). Firm the entire lawn with the back of a leaf rake. Water enough to wet the top of the soil 1/2 inch.

Never use weed and feed anything. Remember that. Your lawn will come around doing nothing more than these instructions. Save your money up to get a sod cutter and remove the entire lawn and lay fresh new sod. No weed and feed.

Never mow below 3", 3 1/2 " is best!

Once you've done your first mow, let the soil dry out a bit. Step on your grass and if and only if the blades stay down then water, and water down at least 2". Let dry until you see your footprints on the the grass. That is the sign to water and water deeply. Don't water until the blades of grass are dehydrated and your footprint stays down.

Aerate once per year by pulling plugs of sod/soil out of the lawn and leaving them where they fall. Rent a machine with your neighbors.

Sharp sharp sharp blades.
Bag your clippings and use them in the compost pile or thinly on the back of plant beds.

While the seed is germinating, only water 1/4 inch to 1/2 inch. Not soggy just moist. You will have to water at least 4 or 5 times on a hot day, a cool day, not so much. Don't allow that seed bed with the germinating seeds to dry out.

After 11 days to 14 days , with decent spring weather, warmth, you should do your first mow. BAG those clippings. This is also the time to do your first fertilizer application (4 per season usually). My favorite even as a commercial lawn person was Dr. Earth's Lawn Fertilizer. A bit more expensive but lasts longer, extended release...also thatch eating bacteria and mychorrhizae fungi. Only 3 applications per season. Amazing stuff.

If this is your home save up for a professional but simple landscape. Raises the value of a home more than a remodeled kitchen or an added bathroom. Hope this revives your lawn. Grins, follow the instructions and you'll be impressed. Mow no lower than 3 to 3 1/2 "! Get a manual 'lift' kit for your mower. Lots of mowers are unable to mow at this height. Warm season grass is very different. Any shorter for cool season grasses and you'll be back where you started.

How long ago did you use this non specific grass and weed killer? You will have to wait at least 3 to 4 weeks to use any seed.

Another option is to get a bid from a grass seed company. They will outline exactly what you can do to get ready and then they spray seed and mulch and guarantee the grass growing. They work with you and closely. Bids are free. Sure learn a lot and get options that you might not have considered.

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  • I used the weed killer about 3 weeks ago so it's time to redo the lawn. You mentioned about "lay fresh new sod. No weed and feed." Do you mean to replace the bad part with new sod anyways? And what is the reason for no weed and feed? Because I am planning to use weed and feed for the non-yellow areas and seed on the yellow areas.
    – HP.
    May 24, 2019 at 18:12
  • Weed and feed products are a combination of fertilizer and sometimes trimec a broad leaf weed killer. One dampens the grass and weeds which are usually broad leaf, not grasses. After spreading this fertilizer cum weed killer, the weed killer sticks to the leaves of the broad leaves and kills the weeds with broad leaves or dicot weeds.
    – stormy
    May 24, 2019 at 20:56
  • If you are going to do this yourself, the next step is NOT weed and feed it is scalping the dead grass right down to the soil with a line trimmer. My tool of choice. Keep the lines even; no longer than 4" for better accuracy. Each one of those yellow spots needs to look like bare dirt. Forget fertilizer for awhile. The grass you have left is in horrid shape. If you are beginning to see why it would be vastly more efficient, less time, less work to get a sod cutter and just cut out all of that sod. Easy to use from the rental store. Cuts away the crowns of the grass leaving bare soil.
    – stormy
    May 24, 2019 at 21:01
  • Then you need to GRADE
    – stormy
    May 24, 2019 at 21:01
  • Rake, grade and roll with a water filled roller at least 3 times. Make sure you don't skip rolling. Now you can either seed with a rotary spreader, hire a grass seed spray company or install sod. I would also get rid of the rocks between your beds and make a clean definitive edge to my lawn by using a flat blade shovel and creating a 'trench' all the way between plant beds and lawn using only simple radii, no compound curves. Also a good time to beef up your plant beds. 3' plant beds are fairly worthless. Personally, I would call a spray seed company to get a bid and advice.
    – stormy
    May 24, 2019 at 21:11

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