Organic crabgrass killer options

theutahn(UT, USA)April 12, 2008

After a few years of organic lawn care, i'm about ready to break down and try something else to kill my crabgrass. My back lawn now is about 25% crabgrass and I need to get this problem taken care of before it spreads further.

I'd love an option other than weed-b-gon and I did some extensive web searching and came up with these.


and here, baking soda is mentioned:

Does anyone have experience with any of these options? I suppose it's not the end of the world if I use one application of weed-b-gon, but I hate to abandon 3 years of organic-only lawn...

Thanks in advance for any help!

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dchall_san_antonio(8 San Antonio)

Are you saying you already have crabgrass in UT?

I was really getting worried when that third link mentioned using Borax, but they did get it right. Borax should not be used outdoors. The other two links weren't very helpful. I have heard of the baking soda solution before. It is not great for the soil, but (supposedly) if you dust the stuff onto moist crabgrass, it is supposed to kill the crabgrass in 3-4 days. By kill I mean it turns black. That does not mean other crabgrass seed is killed. One concern is that water beads up on crabgrass blades, so you would probably have to put some soap into the water you spray first. I guess you could try it both ways. The application method I heard was to put the baking soda into a sock and pound the sock above the wet crabgrass to let some baking soda dust out. That sounded pretty good to me. Then you have to be concerned with what happens to your real turf if the baking soda gets on it. Typically baking soda has been applied as a turf fungicide for a long time and I have not seen any reports of the grass dying. If you try baking soda, whether it works or not, I would come back in 2 weeks with a light application of compost to restore the soil fungi you killed with the baking soda.

Now back to you specifically: I need more info.
What kind of grass do you have/want?
Did you reseed recently?
Is your grass very dense or do you have space between the grass plants?
How high do you mow?
How often do you water?

    Bookmark   April 13, 2008 at 11:27AM
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theutahn(UT, USA)


Not sure if I understand the question; yes, we already have crabgrass. I've been killing it with vinegar or other organic non-selective herbicides but it's bad enough this year that I'd dang near have to kill 1/2 my lawn to get rid of it.

I have a mix of KBG and tall fescue.

Reseed every fall and winter.

Our grass is usually quite dense, but springtime is hard; we will have bare patches where the dogs pee have killed the grass during the winter. And the crabgrass was established before we got here to this house.

Mow at the highest setting.

Water 1x a week, deeply and infrequently. During the hot season, I have to make it every 4-5 days (100+ degrees).

    Bookmark   April 16, 2008 at 6:03PM
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dchall_san_antonio(8 San Antonio)

Okay I guess I have to ask what part of UT do you live in? I'm just surprised you (1) have any crabgrass with those care practices, and (2) have any crabgrass this early in the season. I just read another message where they have it already in PA, so I supposed it happens. I barely have any growing grass way down in San Antonio. So I'm going to guess you're somewhere south by the St George to Green River area.

Anyway, because of the KBG you should not have any bare spots. Dog pee spots can be cleared up with a handful of table sugar sprinkled as soon as you see the spot forming in the winter. The sugar will stimulate the bacteria to breed and actually fertilize the spots in a few weeks. Then the KBG should fill in between the fescue plants. It might even start growing a few weeks after you spread the sugar.

I wonder if you are seeding too late in the season. You can do it right after the summer heat breaks. Depending on where you are that could be late July.

    Bookmark   April 17, 2008 at 1:37AM
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I'm guessing the OP is somewhere along the Wasatch front (the Salt Lake City area). Most of this is roughly zone 6, but it's misleading. The zone designations only tell how cold it gets in the winter, not how hot it gets in the summer or how soon it starts warming up in the spring.

We have mild winters (if you only look at temperature). Severe winters (if you look at snowfall). Grass is turning green here. Even my native grasses (which green up later than KBG) are mostly green.

I don't have crabgrass, but I'm seeing germination in bare spots where I threw seed late last fall (too late to germinate). Seed that I've planted this spring hasn't germinated. My guess is that the crabgrass germinated the same way the grass I planted last year germinated. The weather here is very unusual. It wouldn't surprise me a bit if it's warm enough for crabgrass to germinate. But it's still about a month too early to plant tomatoes and peppers.

My lawn started turning green a long time ago, but I haven't had to mow yet.

It's difficult enough to get native grasses to grow from seed. I don't know how anybody successfully seeds a traditional lawn here. The heat breaks in late August to mid September and we often get snow in early October. The only places that see the heat break in July would be up in the mountains, and those lawns are still covered in snow.

The reason crabgrass can be a problem here, even with good cultural practices, is that we don't need to provide any water to seeds in the spring. Nature does that. But only long enough to get the seeds to germinate. Rainfall averages for Jun-Aug (maybe Sep) are less than an inch a month. Last year, we had two inches of rain the first week of June (very unusual). Then we didn't see precipitation again until October. And I think that may have been snow.

Once a lawn is healthy enough and full enough, the cultural practices can keep crabgrass at bay, but if you've got bare spots in your lawn, you'll get crabgrass (or other weeds).

    Bookmark   April 17, 2008 at 2:57AM
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rcnaylor(z7 Tex)

I'm not sure how well it works as a pre-m, but, with that many annual "weeds" coming back year to year, the place to stop them (besides good cultural practices and overseeding) is with corn gluten meal or other pre-m.

    Bookmark   April 17, 2008 at 7:47AM
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dchall_san_antonio(8 San Antonio)

bpgreen: that's a great overview of your area and issues. Thanks.

I think I would agree with rcnaylor. Even though I have never had obvious results with CGM as a pre-m, I would be using it heavily if I had what is described above.

    Bookmark   April 17, 2008 at 10:46AM
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theutahn(UT, USA)

I'm sorry for the long response time; I've had some connection problems here.

In response to adding sugar to the dog pee spots; we had anywhere from 1-2" of snow on the ground all winter. So it's impossible to see the spots before the snow melts...

BPGreen is correct on all counts. I'm located in Salt Lake City, and growing any grass here is a bear! Wait too long to overseed, and it's too hot and you can't keep it wet to germinate. Too early, and you get routine freezes and snowfall.

Thanks for the tip RCNaylor; the real problem is getting rid of the crabgrass that is present now... It's friggin EVERYWHERE.

Any other opinions on a selective CG killer? I really don't want to use something as toxic as Weed-b-gone, etc.

    Bookmark   May 13, 2008 at 5:00PM
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dchall_san_antonio(8 San Antonio)

...growing any grass here is a bear! Wait too long to overseed, and it's too hot and you can't keep it wet to germinate. Too early, and you get routine freezes and snowfall.

As the Mythbusters say all the time, "There's your problem, lady!" You have your seeding seasons mixed up. If you want to avoid crabgrass, you need to seed as soon as the summer heat breaks. That might be in August or September.

This might be a silly question but do you have a lot of salt in your soil?? You folks in flatlands of northern UT might be the perfect candidates for a soil test done at the Texas Plant and Soil Lab. They are expert at adjusting soil for salt balance. The problem is not too much salt, the problem is the balance of sodium, potassium, calcium, and magnesium. The TPSL's normal test will tell you what to do to correct any salt imbalance you might have. I have seen them turn "sterile" soil into a lush garden with the addition of or the proper salt.

Here is a link that might be useful: Texas Plant and Soil Lab

    Bookmark   May 15, 2008 at 6:45PM
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theutahn(UT, USA)


I've been reseeding in the fall and spring. But it's still tricky; we can have fairly HOT weather up until the weather changes, and then snow on the ground only a few weeks later. It's not unusual to have 100*+ days in august and snow on the ground in october. And to illustrate the point, the past few days have been in the high 90's when we had snow on the ground only a month ago.

I had my soil checked by the local ag university and they didn't see anything wrong with it... But I suppose it's possible it is salty. Our garden grows like gangbusters, as does the lawn when it's doing well; but that also means the dandelions, bindweed, crabgrass, and nutsedge are doing very well. The field next door with the canal is the source of the nutsedge and bindweed I believe.

    Bookmark   May 21, 2008 at 6:44PM
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Kincade--You might want to try dormant seeding. I think I've been getting my best results from the seed that went down late fall and germinated as soon as it warmed up. The window for seeding between too hot and first snow is just too narrow here (I think it was on a Wednesday between 5 and 7 PM last year).

Dormant seeding has a couple of advantages over spring seeding. For one thing, the snows will help carry the seed into the ground. For another thing, it will sprout as soon as it is warm enough, so you'll get a head start on a normal spring seeding. Also, since the soil is still wet from the snow, there should be enough moisture that you won't need to water with the sprinkler system.

I've been trying to replace my KBG lawn with native grasses, but the fall seedings haven't been all that successful. I'm switching to dormant seeding, because I saw some germination this spring in some spots where I threw some seed down late last fall. I think traditional lawn grasses would germinate the same way.

    Bookmark   May 22, 2008 at 1:21AM
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Is there too much to hand pick if you had some neighborhood kids help out? Maybe offer to pay them $5 each and/or buy some pizza? It's a pain but if you can get it partially under control over this summer, you can then use CGM next Spring as a pre-emergent and I think you'd be in pretty good shape at that point. Just a thought.

    Bookmark   May 22, 2008 at 9:39PM
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dchall_san_antonio(8 San Antonio)

You haven't mentioned how you have been fertilizing. Could you go over that?

    Bookmark   May 22, 2008 at 9:53PM
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theutahn(UT, USA)

I didn't realize there had been more posts, sorry for not responding!

BP; I probably will try dormant seeding this fall. That sounds like a good idea!

Buzzsaw; I don't think it's too much to pick, but its that it's HARD to pick. That crabgrass just doesn't pull up like regular weeds, and it's grown in the middle of regular grass. So the whole spot would need to be pulled.

Dchall; I use soybean meal 3-5 times a year, usually at double the usual recommended rate. And when it strikes me, I'll spray the whole lawn with compost tea.

    Bookmark   June 24, 2008 at 7:29PM
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sudzy(5b IL)

HI all mind if we start this thread back up? I really need some help. I had planned on overseeding my front lawn this fall. I'm really not very smart, I guess, I thought there was bird seed spouting in my yard. Looked like little corn stalks. No, just found out it crabgrass. In the last two weeks its become very invasive. The heavy rains, I guess.

Central IL, VERY heavy rains so far this year.
Started Mulch mowing at 3" just this spring. Started "thinking" more organically past year as far as the lawn went. Mulching grass, leaves. (veggie's and flower beds always were organic)
Clay soil, very heavy in some areas.
Grass mix of KBG, ryes, fescue. It's an older lawn. No clue when it was last reseeded. It's in bad shape all around 50% weeds. Backyard is heavily infested in white clover, medic and new this year, alot of wild violet.
I've been here 5 yrs and have done very little fertilizing for past two years. I've tried to keep the weeds down by hand pulling. It's a rental so I can't get crazy with the $$.
The landlord with supply grass seed. Anything else will have to come out of my pocket.
I do compost but none is finished so applying to lawn is not an option.
Would like to start an intensive organic program. I realize it will take a few years to get a respectable lawn. That's ok, I'm not going anywhere.
Main issue: Front yard. Want to reseed. But what about the crab grass?.
Oh, my yard connects to two neighbors and they are full of weeds too. Is this a losing battle? (First two years that I was here, I used weed killer. Didn't work. They can back. I could only fertilze once a year. NOt enough. So I quit. There's gotta be a better way. Hope I'm making sense. It's just so dang depressing. I have a knock-out veggie garden and perennial flower beds that are eye catching. WHY can't I grow grass?

    Bookmark   July 16, 2008 at 1:58AM
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Do you treat the lawn with as much care as your garden and flower beds? LoL. You will do well with the lawn if you reseed and let the grass outcompete the weeds. Mow at 4" if you can, water infrequently but deeply (the rule of thumb is 1" per week) and fertilize. If you can core aerate then that would be better. There are many threads on the lawn care forum about renovating a lawn and you may want to read those.

With weedy neighbors you'll have more than your share of weed problems, but generally neglecting the basics is a bigger cause of weeds.

    Bookmark   July 16, 2008 at 7:53PM
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My first visit to this forum--I'd planned to search, but I didn't need to.

I have a patch of crabgrass on basement backfill dirt, hard as brick. It's only about 8' x 5' but spreading as crabgrass does. I've never made ANY effort with that part of the yard, but I've come around to it. I covered it with cardboard, and thought I'd sheet compost over it and fork it next spring to pull out the crabgrass roots, after the soil is a little looser.

Will it all survive? Will it just thrive under the sheet? Should I get serious and bite the hard, sweaty bullet and fork it out now?

    Bookmark   July 18, 2008 at 10:11AM
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Sudzy in Illinois and Petalpatsy in may get more help and replies if you each start a new thread.

Just a helpful suggestion.

    Bookmark   July 29, 2008 at 3:04PM
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sudzy(5b IL)

Hey Sandra: And a very good suggestion it is. :) But, as for me, I've given up. I don't think it's possible for me to have a really nice yard. So, I decided just to do no harm. I mulch mow and will mulch some leaves on it this fall. Can't water, way too expensive. And I'll dormant seed over winter. I'll have to just learn to live with my crappy yard. Thanks for the tip though. Smile

    Bookmark   August 6, 2008 at 1:05AM
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just moved in crab grass everywhere. garden is my main concern at this point. Help please

    Bookmark   March 2, 2011 at 9:45PM
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This may be a little late, but there is an EXCELLENT organic crabgrass killer on the market. It's called GARDEN WEASEL CRABGRASS KILLER. The active ingredient is Cinammon. I personally can testify that this product works GREAT! I have St. Augustine here in Houston, TX and it did wonders on my crabgrass and Virginia Buttonweed. Just apply it per the instructions. It took about a week for the Crabgrass to die out. After applying you have to keep it dry, so make sure theres no rain forecast and dont water. Just Google this product to find out how you can have it sent to you. Good luck!

    Bookmark   April 1, 2011 at 11:30PM
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dchall_san_antonio(8 San Antonio)

Debra, don't get confused by the labeling. solc has been persuaded that the cinnamon is what causes the weeds to die. The active ingredient listed on the label is cinnamon, but the ingredient that kills crabgrass is baking soda. If you have any type of grass other than St Augustine, baking soda will kill your grass, too.

So we must ask where you live and what kind of grass you have? Also it is kind of early in most of the country to have crabgrass everywhere, so there is more than the professional curiosity as to where you live. You might have another weed that they call crabgrass in your neighborhood. A picture would be helpful so the right solution could be found.

Whatever you do, please don't do anything until you have identified the weed. Another guy used Round Up to kill his weeds and killed his entire lawn. You have all summer to fix this, so take a few deep breaths and get it right. For example you might have used that baking soda product and killed your entire lawn.

    Bookmark   April 6, 2011 at 10:59PM
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I will put in another plug for corn gluten meal as a pre-emergent treatment for crabgrass, but I've learned that it must be put down very early in the spring, right when the forsythia starts to bloom here in the mid-Atlantic. I dont know what the trigger would be in the west, but surely your ag extension office can supply that information. The manufacturers all recommend a re-application in late summer or early fall, but that's when I reseed my lawn, so using a pre-emergent would be counter-productive. I have found that after using corn gluten meal for several years, I have less crabgrass each year. Plus it's a good fertilizer. Try to apply it just before a gentle rain.

    Bookmark   June 3, 2011 at 10:16PM
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My "recipe" for killing weeds is a gallon of white vinegar, a 1-lb box of salt, 4 tablespoons of lemon juice and two squirts of dishwasher detergent. Dissolve salt in boiling water. Mix all ingredients. Instead of a spray bottle, I use one of those plastic ketsup/mustard bottles with the spout clipped just a bit. You cannot control spray, but with a steady stream, you can pour the mixture exactly where you want it. I have some crab grass. It killed it within days but now I see that some has sprung up again, so another dousing is needed.

    Bookmark   September 3, 2014 at 8:13AM
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Crab Grass is an annual "weedy" grass that germinates from seed when the soil temperatures and moisture levels are just right. A pre emergent, such as Corn Gluten Meal, can help prevent seeds from rooting and plants from growing, if applied right (enough at the right time).
Those seeds can lay there waiting and can germinate anytime not just in early summer, so new plants can appear anytime during the growing season.
A lawn, growing nice and thick, in a good and healthy condition is the best defense because a good thick turf will shade the soil and keep that soil temperature lower then what the Crab Grass needs to germinate.
Not all options for killing Crab Grass are acceptable to organic growers since some are quite harmful to the environment, much more so then having Crab Grass in the lawn or garden. Mechanical removal is the least environmentally destructive and most efficient and if done before the plants set seed allow composting of the plants which is even more environmentally acceptable. While vinegar, by itself, will kill Crab Grass even that can be an environmentally unsound practice and there is no good reason to add other materials to the vinegar.

    Bookmark   September 4, 2014 at 7:32AM
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