How to differentiate the crabgrass and weed?

coodyMarch 24, 2009

This is regarding to the crabgrass or weed grown well already. How to differentiate them? Should the crabgrass and weed be treated/killed separately? If so, which one should be treated/killed first or they can be treated/killed at the same time?

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billhill(z5 MI - KBG)

Yes the crabgrass and the weeds already growing are two different kinds of weeds. Crabgrass and other grassy weeds are classified as grassy weeds. Dandelions, spurge, henbit, thistle, black medic and many others are classified as broadleaf weeds. Each classification is treated differently. Grassy weeds including crabgrass are best controlled before they sprout up into your lawn. Granular Pre-emergent herbicides for crabgrass are used for that purpose. Broadleaf weeds are killed after they are already growing by using a liquid selective herbicide targeted for your growing weeds. Both kind of weeds are treated separately. I hope this explanation helps.
Bill Hill

Here is a link that might be useful: Dandelions and Broadleaf Weeds

    Bookmark   March 25, 2009 at 6:40AM
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coody

billhill said, "Grassy weeds including crabgrass are best controlled before they sprout up into your lawn. Granular Pre-emergent herbicides for crabgrass are used for that purpose." If missing to control the crabgrass before it sprouted up into the lawn, how to kill it, still using the granular Pre-emergent herbicides or the different killer product? Can you show the pictures to show the difference between the crabgrass and weed, by the way?

    Bookmark   March 25, 2009 at 12:10PM
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bpgreen(5UT)

If it has already sprouted the pre emergent will not do anything. Most herbicides that will kill crabgrass will also kill your lawn. You can spray something on it (but that will kill any grass it hits) or you can pull it.

Anything granular weed killer that you'd spread will be for broadleaf weeds (like dandelions, etc). The granular stuff usually gets spread over the whole lawn, but once the weeds have sprouted, I think it makes more sense to spray only where the weeds are. For a pre emergent, it makes more sense to spread over the whole lawn since the weeds can sprout anywhere.

Crabgrass is a weed, so I'm not sure what kind of picture you want. There are too many weeds to show a picture of every weed. If you're trying to identify a specific weed, you can post a picture here and somebody will probably be able to identify it.

    Bookmark   March 25, 2009 at 3:28PM
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billhill(z5 MI - KBG)

If you missed the opportunity to spread Pre emergent than you can try to kill it using post emergent selective herbicide intended for crabgrass. This practice is not nearly as effective as spreading pre-emergent herbicide for crabgrass. Sorry I don't have pictures of crabgrass. A search on google will find many.

    Bookmark   March 25, 2009 at 3:50PM
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coody

I still cannot identify the crabgrass, for example in the pictures provided by chrisstl at http://forums2.gardenweb.com/forums/load/lawns/msg0311002816103.html?19 from his problem lawn. I just saw the grass and bare spots. Where is the crabgrass and how did you identify it? However, I learned the crabgrass is one of weeds and seems being unable to be killed by any herbicides unless killing the lawn too if the crabgrass has already sprouted up into the lawn. Is it correct?

    Bookmark   March 25, 2009 at 8:30PM
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rdaystrom

Depending on your grass type MSMA will selectively kill Crabgrass and not harm the lawn.

    Bookmark   March 26, 2009 at 3:25AM
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tarheel23

You shouldn't have crabgrass yet. It's a warm season weed. I guess it's possible if you're in the very deep South, but I doubt you have crabgrass yet. You can go ahead and put out a pre-emergent now. It will prevent weed seeds from germinating for about 10 to 12 weeks. So you'll probably still get some weeds mid to late Summer.

You're kind of in between the two pre-emergent applications for synthetic lawn care. The first should go down in the middle of February to control cool season weeds. The second should go down mid to late April to control crabgrass. The second should not contain fertilizer.

    Bookmark   March 26, 2009 at 8:07AM
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coody

Does the crabgrass have flowers? Since crabgrass is a weed, why can the herbicides kill the weeds only but it is hard to kill the crabgrass without killing the lawn? IsnÂt there post-emergent selective herbicide intending for the crabgrass? IsnÂt there any herbicide for killing both of the weeds and crabgrass without killing the lawn? Does anyone know it?

    Bookmark   March 26, 2009 at 11:34AM
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bpgreen(5UT)

Technically, I suppose crabgrass has flowers, but they're not flowers in the sense that you'd normally think og flowers. They're like other grass seed producers (including corn).

The reason crabgrass isn't as easy to kill in a lawn is the second half of its name (grass). There are a lot of weed killers that will kill broadleaf weeds (think dandelions, etc). Those will kill plants that have broad leaves (but be careful, because plants like shrubs, trees, garden plants, etc also have broad leaves). Since crabgrass is a kind of grass, those weed killers aren't effective on it. From some of the other comments above, there are apparently some crabgrass killers that will work after the crabgrass has sprouted. MAke sure you read the label carefully so you know it's safe on your other grass.

I've really never worried too much about crabgrass. I've gotten it in a few places, but it doesn't live long and if I can get the grass around it to fill in, the crabgrass doesn't have anywhere to sprout.

I found some in my lawn yesterday (it's snow covered today) so I'm not convinced that it can only be sprouting in the deep south. The reason I've got some now is that I let much of my lawn die last year for reseeding and it hasn't all filled in. By next year, I think the lawn will be thick enough to prevent any crabgrass from sprouting.

    Bookmark   March 26, 2009 at 12:38PM
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coody

Thanks bpgreen for your good comments. I looked at the herbicide products for the crabgrass in the store. I saw only three intending for the crabgrass, Pre-emergent, Control(some brand name product) and Halt (Scotts). We have already known what the pre-emergent mean. How about the Control and Halt herbicide? Are they the post emergent herbicide or the same as the pre-emergent herbicide? By the way, can we see the colorful flowers on the crabgrass, just like the henbit with the purple flowers or the crabgrass never has colorful flowers? Can anyone explain it?

    Bookmark   March 26, 2009 at 9:31PM
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bpgreen(5UT)

Halts is another pre-emergent.

I don't know what Control is. Who makes it?

If you're seeing colorful flowers, you're not seeing crabgrass.

Can you post a picture of the weed you have?

    Bookmark   March 26, 2009 at 11:15PM
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garycinchicago(Z5 Chicago IL.)

Try this link below

Here is a link that might be useful: Turf Tips - Crabgrass Control in Home Lawns

    Bookmark   March 26, 2009 at 11:32PM
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rdaystrom

I already told you about a post-emergent herbicide for crabgrass. It's MSMA. (Monosodium acid methanearsonate) You need to tell us what kind of grass you have because you can't use just any herbicide. If you want to see crabgrass go to google or yahoo and do an image search for crabgrass.

    Bookmark   March 26, 2009 at 11:39PM
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tarheel23

Again. Crabgrass is a warm season weed. You don't have it yet. Put out pre-emergent now to control it later in the Summer.

    Bookmark   March 27, 2009 at 9:02AM
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coody

I do not know what type of grass on my lawn. Since crabgrass has never had colorful flowers (as bpgreen said), it may be always green, right? As a result, I may not be too worried about it. Weed, however, such as henbit with purple flowers is different. It looks not good in the green grass and it must be removed as quickly as possible.

Rdaystrom, where did you see the post-emergent herbicide MSMA. (Monosodium acid methanearsonate) sold? I intend to look at it in a store.

    Bookmark   March 27, 2009 at 3:18PM
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rdaystrom

I have seen MSMA in stores like Lowes, Home Depot, Tractor Supply, local farm supply stores, WalMart, and even Albertson's. You may need a herbicide with 2-4D in it or a combination of 2-4 D and MSMA. Sometimes it's just called crabgrass killer. Herbicide companies try hard to disguise their products by calling them by there own made-up Brand Names. I always read the ingredient labels. Go somewhere that has a good selection of herbicides and read the ingredients, and instructions to find out what they are used for and what grasses are not affected. You can educate yourself this way. Research herbicides on the internet. There is a lot of information out there on the subject.

    Bookmark   March 28, 2009 at 12:01AM
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garycinchicago(Z5 Chicago IL.)

> "I do not know what type of grass on my lawn."
>

How about the question "where do you live?" You keep ignoring that question when asked.

Now nobody wants your address, we're not coming over!
We can help you better if you gave a little hint like I'm in the north suburbs of ____, that's all.

    Bookmark   March 28, 2009 at 1:41AM
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davidandkasie(Z8 MS)

if you live in my general area, you CAN have crabgrass by now. i know, i have it already. of course, most of the last month or so we have had temps at or above 80F. i would venture to say that roughly 2 acres of my property are either crabgrass or clover, or both. luckily it is the part i ain't worried about. and soon i won't have to worry about it as that area will be a horse pasture soon as i can get the fence up. he will take care of it for me.

Here is a link that might be useful: shows all the atages of crabgrass

    Bookmark   March 28, 2009 at 11:17AM
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davidandkasie(Z8 MS)

boy, my highschool typing teacher would have my head! that link is supposed to be titled "shows all STAGES of crabgrass"!

    Bookmark   March 28, 2009 at 11:18AM
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coody

Can you help to identify the crabgrass? I think it is the crabgrass because of its wide leaf, right? I saw a few in my lawn but not many as the weeds are. If it is, it can be removed because of not so many. However, it is not the same easy to pull the weed out because the crabgrass has a big root comparing with the weed. How do you remove the same crabgrass from your lawn?

Here is a link that might be useful:

    Bookmark   April 2, 2009 at 2:16PM
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bpgreen(5UT)

That's not crabgrass. It might be tall fescue or some kind of grassy weed. I'm not really good at identifying the different kinds of grassy weeds, but I can recognize crabgrass and that doesn't look like crabgrass.

    Bookmark   April 2, 2009 at 2:50PM
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coody

I do not know what type of grass or grassy weed. The most of grass leafs are thin and short and they have not changed to green yet. But, several grasses or grassy weed are green. They are a little tall and their leafs are wide. They grow very well. What are they? I post another one for identification. See linlk.

Here is a link that might be useful:

    Bookmark   April 2, 2009 at 3:56PM
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bpgreen(5UT)

Maybe somebody else can tell you for sure. It looks like tall fescue to me.

It doesn't really make a lot of difference, though. It's a grassy weed, so you'll probably need to use a non-selective weed killer like glyphosate (Roundup is the best known brand name of this).

Just remember that it will kill whatever it hits, so don't spray it on the entire lawn or you'll kill all the grass, including the grass you like. Only spray it on the stuff you want to kill.

    Bookmark   April 2, 2009 at 5:35PM
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coody

I just dug out one with a shovel http://i40.tinypic.com/21j7k0h.jpg
The root is big. If using the Roundup to kill the grassy weed or the tall fescue, I know it will change to yellow very soon. I wonder whether it will be killed forever; whether its root will be killed; whether it will grow up again sometime later.

    Bookmark   April 2, 2009 at 8:45PM
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davidandkasie(Z8 MS)

RU will kill the root. it will not kill any seeds inteh ground though. you will need a preemergent for that, in my area you can still put out pre-em for the 2nd round of weeds.

    Bookmark   April 2, 2009 at 9:08PM
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