I applied moss killer and the moss turned black in numerous places on my lawn but especially in a couple of shady 3'x 3' patches. But I have read a couple of articles saying that moss isn't that bad and it's ok to leave it alone.

Since the patches are shady, moss probably is the best thing for them and grass probably won't grow easily there. So if I wanted to "undo" what I just did and have the moss come back, should I just leave it alone and wait for the moss to come back? I don't want dandelions and other weeds to appear there instead.

  • 1
    How long ago did you apply the chemical, and which chemical did you use?
    – michelle
    May 20, 2014 at 13:49
  • 1
    If it's copper compounds, leaching is the only method, ie water and time. May 20, 2014 at 15:31
  • @michelle I used Moss Out about a week ago (18.6% Ferrous Sulphate). May 20, 2014 at 16:43

3 Answers 3


As you've treated the moss with ferrous sulphate, wait 4-6 weeks, rake out the dead moss, then I'd use grass seed, a shady mix (though I've no idea what kind of grass you're growing), scratch up the surface on the bare parts to give an inch of friable soil, then broadcast the seed. Keep watered - whether it grows well or not is irrelevant - the idea is to stop weeds colonizing it until moss reforms during wet spells/autumn/winter.


Moss control, if it was ferrous sulphate, will bring your soil pH down...more acidic. Lawns prefer a pH slightly more alkaline. Do a soil test to show what the pH is and then add lime to raise the pH using the directions on your packages and whatever grass that you have find the best pH range for your type of grass. I'd divide the total amount of lime by 2 or 3 and do separate applications, testing the pH each time. There are also inexpensive kits but a soil test through your county extension service should be free or low-cost.

Don't forget to aerate at least once per year...pull plugs and let them dry out on your lawn. I've found organic fertilizers that although they take longer...they last longer and they also have bacteria included to assist in decomposing thatch. Unless you have a true mulching mower, I'd bag my clippings. Also, find out how high your grass should be cut for maximum health to be able to shade the soil, out compete weeds (moss is an opportunist...if there is bare ground and plenty of water...you'll get moss...you were right. Moss doesn't have a chance competing in thick, vigorous grass).

Water INFREQUENTLY, when you water SOAK the soil down to 6" and allow the lawn to dry out until when you step on the grass the blades don't pop back up...then water again. Depending on your type of soil this is about an inch of water per week. Our grasses in the pacific northwest have huge root systems and without top growth of at least 3", the grass isn't able to support its own food storage system, the roots. Watering infrequently but deeply trains your grasses to be drought tolerant. In between waterings shallow weed grasses and moss have no chance to germinate.

Dr. Earth's lawn fertilizer was incredible. I only fertilized twice a year and my lawn was the darkest green in town.


Any of the moss that has turned black has already been killed. There's a few different formulations of Moss Out. The one for lawns contains ferric sulfate as the active ingredient. It can persist in the soil for quite some time and I don't think you can leech it out with water. Other Moss Out formulations use either ammoniated soap of fatty acids or zinc sulfate. The ammoniated soap of fatty acids is the most biodegradeable but I think what's done is done.

I had some moss in a part of my lawn a while ago. A number of factors contribute to moss growing including compaction, not enough sunlight, low pH, etc.

Send a soil sample in for analysis, not too much money, to get a better sense of the fertility and pH of the soil and make appropriate corrections.

To deal with the compaction you should core aerate. You can hire someone to do it, rent a machine and do it your self or you can buy a manual core aerator. I have a review and instructions for the Turf Hound Aerator on my site. It's what I used to deal with my compaction issues. It's good to have to hit trouble spots if you don't aerate every year.

After core aerating spread some compost over the area. About 1 cubic yard per 1,000 sq feet. Raising the organic matter of the compost will help alleviate compaction as well. If spreading around all the compost isn't appealing I've read and seen good results with regular compost tea sprays after aeration though don't have much experience with it myself.

Since it's shady, the soil won't dry out quickly after a rain. If you can keep people off of it during and a couple days after rain it would help.

After topdressing with compost overseed with a good shady lawn mix that will be primarily composed of fine fescues. Make sure it has some creeping red fescue in it because it's a spreading type grass unlike other fine fescues. I have some shade grass seed recommendations on my site as well. You're near Oregon where much seed is grown so you shouldn't have a hard time finding a good blend.

I believe there's still time in your area to overseed before it gets too hot so you can try it since fine fescues germinate fairly quick. If it comes in patchy overseed again in the fall.


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