Use these simple methods to prevent and kill crabgrass, and avoid the big mistake that most people make in their lawn care program.
Come mid summer you’re probably starting to see some of the negative effects the heat can have on your landscape. Your lawn is probably the part of the landscape that has you most frustrated.
As summer heat creeps in the more desirable grass types struggle, while weeds such as crabgrass thrive. Crabgrass can quickly take over your lawn and if you wish to have a crabgrass free lawn then crabgrass prevention, and removal should be a part of your lawn care program.
What Is Crabgrass and Why Is It Bad?
Crabgrass is an unattractive annual weed that enters your lawn (usually through bare spots). It’s coarse texture and variation in color makes it stick out and prevents you from achieving a uniform looking lawn. It is a problem weed in both cool season and warm season lawns.
When Does Crabgrass Germinate?
Crabgrass can germinate when ever soil temperatures are ideal. Once soil temperatures hit 55 degrees crabgrass seeds begin to germinate. Peek germination is around 65 degrees, and once soil temps are in the high 70’s most crabgrass seeds that are in the soil should already be germinated. When soil temps are in the 80’s it’s too hot for crabgrass and most other broadleaf weeds to germinate.
During the summer and early fall, crabgrass will drop its seeds. The seeds remain in the soil over the winter and germinate the following season as soil temps warm up after the winter.
The summer months is when you’re likely to see crabgrass thrive. This is what confuses people into thinking that new seed is germinating but that’s not the case. At this point, what you’re really seeing is the already germinated crabgrass becoming more mature as it flourishes during these hot months and outcompetes the rest of your lawn, especially for those with cool season grasses.
What Does Crabgrass Look Like?
Crabgrass has to be the most misidentified weed there is. Pretty much anytime there is a grass like weed with wide leaf blades people call it crabgrass. This is a serious problem though since there are many other undesirable grass types that resemble crabgrass but won’t react to the same treatments.
Tall clumping fescue for example might look like crabgrass at first glance but it is very different and requires different control methods.
Crabgrass is usually light green in color and stays low to the ground, usually landing underneath mower blades depending on height of cut. The only part of the weed that grows tall is the stalk which carries tiny flowers that eventually turn to seed.
For a more in depth look on identifying crabgrass check out: Organo-Lawn
Prevent Crabgrass With Pre-Emergent Chemicals
Of all the lawn care products out there, pre-emergent chemicals are probably the most misunderstood and misused.
Most people rush to the stores the second the weather starts to get nice in early spring, and they load up on a step 1 product that most fertilizer companies push.
The step 1 for most of these companies contains a crabgrass pre-emergent and a fertilizer all in one. On the label you can find a very broad time frame of when you are supposed to apply.
There’s nothing wrong with applying a step 1 product to your lawn. But for it to be fully effective you have to have an understanding of soil temps.
If you’re looking for a simple crabgrass pre-emergent strategy then apply the step 1 twice. Your first application should be when your soil temps are approaching 55 degrees, and your second application should be about 5-6 weeks later as soil temps approach 70. This is a fine strategy if you want to keep things simple.
If you’re looking for a more effective pre-emergent for crabgrass as well as other broadleaf weeds then consider using the following products at the correct soil temperature:
1. Dimension: Dimension (active ingredient Dithiopry) is a next level pre-emergent that is used by professionals. Dimension can be found in a couple of different products but my favorite and most accessible for homeowners is Lescos 19-0-7 Crabgrass Preventer.
Apply this product for your first two applications using the same soil temperature rules above (approaching 55 and 70).
I actually recommend applying this product for a third time heading into fall when soil temps are decreasing. This will prevent Poa Annua and other fall broadleaf weed seeds from germinating. Check out: Lawn Care Schedule Using 3 Products
One other benefit of this product is it does provide some post-emergent weed control in addition to pre-emergent. So if you’re getting a late start and you’re afraid you missed the early 55 degree soil temperature go time window, then using Dimension could help knock out some broadleaf weeds that have already begun to germinate.
Another great crabgrass pre-emergent is Prodiamine. Prodiamine is the name of the active ingredient so it can be found in several different products. It’s commonly found in a product called Barricade. To make things less complicated just know that Barricade and Prodiamine are the same thing. If you see a fertilizer that says ‘Fertilizer plus Barricade’ you know you’re getting Prodiamine.
Also, if you are in New York, or other states where Dimension is restricted, then Prodiamine products will be your best option.
You can buy Prodiamine 0-0-7 which is pretty much just straight Prodiamine with a little Potassium here: Prodiamine 0-0-7. Just note this product doesn’t contain any nitrogen. If you’re looking for a fertilizer and prodiamine pre emergent all in one then check out this product: The Andersons 19-0-6 with Barricade.
There are several other products out there that contain Fertilizer and Barricade, feel free to check out what your options are locally.
Pendimethalin is the pre-emergent you’re most likely to see in the step 1 programs such as Scotts. Honestly, there’s nothing wrong with Pendimethalin and if that’s what you choose to use for one, or your first two applications then that’s fine. But most professionals would agree that Dimension and Prodiamine are superior to the Pendimethalin.
If you’re new to lawn care or you’re getting too confused and don’t know where to begin, then keep it simple and just apply Scotts Step 1 for your first two applications. Just stick to the soil temperature guidelines (approaching 55 and then again at 70).
Soil Temps Are Crucial
Crabgrass starts to germinate when your soil temperature hits 55 degrees. The best thing you can do is find out when your soil temperature usually hits 50 degrees and apply your crabgrass pre-emergent then. If you apply when soil temps are at 50, by the time it hits 55 the pre-emergent will already be in your soil.
You’re probably wondering how you’re supposed to know when your soil temperature is 55 degrees. Luckily, there is a great site called Green Cast Online.
All you have to do is go to the site and enter your zip code. Look at the five day average and when it hits 50 degrees it’s time to throw down your first application.
About 5-6 weeks later you want to apply another round of pre-emergents as soil temps approach 70.
Once soil temps go above 80 degrees crabgrass germination comes to a halt. Adding a pre-emergent at this time won’t be very effective. I should point out that at the end of summer as soil temps fall back down to 70 degrees there are fall germinating broadleaf weeds that can pop up. That’s why I recommend a third application of pre-emergents heading into fall.
For a better understanding of soil temperature and how it should be used in you lawn care program check out: The Importance of Soil Temperatures in Your Lawn
Spot Treat to Kill Crabgrass
While prevention is definitely the best method for managing crabgrass, it is likely you will still have some clumps of crabgrass that find a way into your turf. It is usually in the most vulnerable locations within your lawn.
The best way to kill crabgrass that is already established is to spot treat using a liquid, lawn safe herbicide such as Ortho Weed B Gone Plus Crabgrass Control. A product like this is easy to apply and best of all it will kill crabgrass without killing your lawn surrounding the crabgrass.
I recommend going out and walking your lawn once a week to spot treat new clumps of crabgrass that pop up.
If you have a more serious problem, meaning crabgrass is more mature or widespread, then I recommend using a product called Tenacity. Tenacity is a more professional product that works a little differently. It blocks photosynthesis from occurring in lawn weeds.
It is a selective herbicide so it will kill crabgrass and other lawn weeds without killing your lawn. If you have crabgrass everywhere then you can blanket spray your entire lawn with Tenacity.
When spot treating or blanket spraying, make sure conditions are dry so the herbicide sticks to the grass blades. Also, make sure you don’t apply before rain, or right before mowing. You want the herbicide to have time to do its job.
With enough persistence, you will eventually win the battle as the crabgrass dies off and your lawn fills in from routine fertilizer treatments.
Manually Remove Crabgrass
If you just have some random crabgrass weeds that pop up here or there then consider manual removal. Sometimes I don’t have the patience to wait for chemicals to kick in. I prefer to get rid of it the moment I see it. The trick here is to manually remove crabgrass before it gets too big.
If it’s just a small weed simply pull it out by hand or use a really helpful weed pulling tool . If there is a more substantial patch then you have to dig it out using a shovel and that will create a bare spot in your lawn.
Removing smaller crabgrass weeds is definitely easier and better for your lawn!
Maintain a Healthy Lawn
It’s true. Nothing is better for combating lawn weeds then maintaining a healthy, full lawn. Sticking to a good lawn care program will allow your lawn to out compete crabgrass.
An established lawn with no bare spots makes it a lot harder for weeds to gain traction. If you have bare spots in your lawn then consider repairing them by top dressing.
Also, mowing tall and often is a great way to prevent crabgrass. Mowing tall will allow your lawn to block sun from reaching the low growing crabgrass. Mowing often will prevent stalks from forming flowers which eventually become seeds.
The Biggest Mistake Everyone Makes
Overall, the biggest mistake I see most homeowners make is applying crabgrass pre-emergent only once in early spring. Applying 2 applications 5-6 weeks apart is crucial!
Applying pre-emergent twice allows you to not have to worry about your timing so much. It can be hard to predict when crabgrass will germinate so applying 2 applications of pre-emergent takes away a lot of the guess work.
It also ensures that there is plenty of pre-emergent in your lawn over a longer period. This is important since there is a long period in spring/summer where crabgrass has the ability to germinate.
If you think crabgrass has taken over your lawn and the only way to fix it is to rip everything out and start over, you need to check out: Top Dressing Lawn: Benefits and Advice.
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