How soon after applying pre-emergent crabgrass control can I...?

10 years ago

I applied Scott's Halts Plus early spring as usual and now need to sow some grass seed in bare spots. How soon after applying this product can I sow seed? Thanks.

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bvisailor

10 years ago

My topsoil/seed/topsoil plan worked BEAUTIFULLY. Most of the seed germinated, except where rain washed the soil away entirely. I put down WAY too much seed, figuring that half of it wouldn't grow, but it did!
I've mowed it 3 or 4 times already and it has transformed our pitiful backyard. The fact that we've had tremendous amounts of rain helped, because I could never keep it as wet as Mother Nature does.

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Comments (9)

grass1950
10 years ago
It should say on the bag. I believe Halts requires 120 days after app. before seeding.
bvisailor
10 years ago
I had this same issue, so I top-dressed the bare spots with as much topsoil as I could, seeded the heck out of it with way too much seed, and dusted a little more soil on top. I'm hoping at least a little of it survives, but we'll see.
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Terps: I think that you may be crediting crabgrass with being a thinking creature, which it is not. Or you may be thinking that Pre-M "prevents" germination, which it does not - even though the name is "pre-emergent". Crabgrass seeds germinate when there is adequate moisture (think April showers) and proper soil temperatures. The Pre-M does not "delay" the germination, and the crabgrass seeds can't really "outlast" the Pre-M's effectiveness. The Pre-M works by preventing root formation after the grass has actually germinated. With no root system, it wilts and dies before you even see it. No second chances, no waiting for the Pre-M to lose it's effectiveness. It's germinated and dead. The only crabgrass that makes it is if the conditions for germination don't happen before the Pre-M barrier breaks down. If you want to bet that we might not get 60 degrees and wet weather before 90 days from now, than put down more at the beginning of Summer. I'm saving my money to use the additional Pre-M in very late Summer to prevent the Poa Annua germination period (which will overwinter and be NEXT Spring's headache).
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I wonder where these ideas generate from. You have a mix of things going on. The time to apply any preemergent is prior to your yard reacting to the spring time weather. The forsythia is usually the first indication of the events of spring. Thus the earliest blooming of the earliest forsythia is the trigger. You are already late for this year. The "good news" is that crabgrass will germinate under proper watering and sun conditions all summer. Chemical fertilizer should not go down until you mow real grass twice. By waiting you will ensure that you are fertilizing your grass and not your weeds. When you apply has nothing to do with root or leaf growth. I'll tell you what has everything to do with leaf AND root growth, AND it controls your weeds to boot, is setting your mower to the highest setting. By growing longer leaves you will grow deeper roots. Deeper roots can get water deeper in the soil, so you can water more deeply and less frequently. Tall grass shades the soil keeping it cooler and less prone to evapotranspiration of the moisture, so you water less. You don't have to use a weed-n-feed. You don't have to do anything until you mow (tall) twice. Then use regular fertilizer. By then some of the winter annual weeds will be dead anyway. By letting your grass grow up tall, weeds like dandelions will die out. Why? Because the surrounding grass will force the broad dandelion leaves to point up and they don't get enough sunshine. The plant will die. Any seeds that blow off the dandelion will not be able to get down to the surface through the tall grass so no new ones will crop up. And if they did hit the surface, and you did water them daily so they would sprout, the tall grass will provide enough shade that the seedling dandelion will not get enough sunlight to take root. If you fertilize in a few weeks, many of the weeds will be gone by then. Then in two more weeks, a few more weeds will be gone but the remaining weeds will be healthy enough to absorb a spot spray like weed-b-gone. This is a less expensive idea than the weed-n-feed and seems to work better. But if you water infrequently and deeply, and mulch mow at your mower's highest setting, you should not have crabgrass this year regardless of your use of preemergents. Mother Nature can throw you a curve and apply enough water to germinate the crabgrass, but that is not the end of the world. The tall grass will severely curtail any spread and may choke it out. It needs plenty of sun to thrive.
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Well, you've painted yourself into a corner. All the chemicals are certainly going to inhibit new grass from growing. Removing the top layer of soil would certainly work. Sodding would certainly work. Really raking the area well and mixing up the top layer of soil will limit the effectiveness of the premergent, but won't eliminate it completely. Personally, this is what I would do. 1) Mow the area as short as possible and bag up the weed scraps 2) Use a rake or hoe to rough up the first 2 inches of soil. 3) Seed the area with perennial rye. It germinates super fast and will be easy to kill this fall when you renovate the area properly. In the fall, round-up the whole area and start fresh.
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Last year, the crabgrass pretty much took over a 15x12 foot section of my front lawn. The crabgrass moved in after that section got churned up by a skunk looking for grubs - crabgrass tends to take hold in disturbed soil. I didn't want to use herbicides, especially since I applied nematodes to deal with the grubs. So I waited until the crabgrass was of a size to handle easily and then got on my hands and feet and yanked it all out by the roots. When I was done the entire section was pretty much all open soil, with very little grass surviving. I overseeded and the grass came in very nicely. However, I had no illusions that there were a million seeds in there, which is what prompted my post. This spring, then, I did use the pre-emergent and CGM. I wish they didn't feel that they have to add fertilizer to the preemergent but that's all I could find. I used CGM to further suppress germination but also to try to even out the areas that didn't get pre-emergent/fertilizer. I still ended up with some patches but that's sorted itself out by now. So far, I've not seen any crabgrass in the lawn and the area that I've reseeded looks absolutely wonderful. In fact, it's come in so thick that I've had a bit of a chore trying to mow it with my reel mower. Time to sharpen those blades! :)
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indy_hawkeye
10 years ago
ponesy...please let me know how your reseeding goes. I was thinking about a similar approach to bare areas in my back yard. My Bermuda got hit hard last year with army worms and this year is a recovery year. I hit it with Halts about 60 days ago and was looking to reseed ASAP.
bvisailor
10 years ago
I will- it's only been a few days & I think fescue & KBG take a week or 2 to germinate... which reminds me- I think Bermuda takes about 30 days to germinate, so keep that in mind- will be hard to keep it damp long enough for germination in the middle of summer. :/
enigma7
10 years ago
Fescue is about a week but KGB is much longer (close to 3 in my experience but I only seed in the fall and so temps likely affect this).
Alfredia
8 years ago
bvisailor- want type of seeds did you put down and topsoil?
PSU4ME
8 years ago
Just an FYI, thread is from 2013 so they may not respond. Maybe start a new thread with you question/situation?
dchall_san_antonio
8 years ago
But I'll respond. Please don't do what bvisailor did. If he/she had any long term success it was because the heavy rain washed all that top dressing away.

Generally now is a poor time to put fescue, rye, or Kentucky bluegrass seed down. It also happens to be a poor time for bermuda, but for a different reason. So now is a bad time to seed. If you put bermuda down now nothing will happen until mid May when some of it starts to germinate. Then in June the rest of it will germinate. That's the only reason it takes 30 days is because most people SERIOUSLY jump the gun. If you are seeding with fescue, rye, or KBG now, you're also going to germinate all the crabgrass seed in the yard. Furthermore grass seeded now will not develop heat resistant roots by the time summer comes. The result is a crabgrass lawn by July.

If you go ahead and seed now anyway, you don't need any topsoil. Grass seed sprouts at the surface. All it needs is continual moisture (just like crabgrass seed needs) for several weeks. The best time to do this is in the fall if you can stand to mow weeds until then. There are a few other tricks we can help you with.

What do you want to do? If you want to do it now, we'll help you with the tricks and all the details. If you want to stretch through to the fall we will help you have the nicest weeds on the block until then ;-) Nicest weeds on the block is what I've had for the past 2 years. I'm patiently waiting for my grass to spread and take over the weeds.

How soon after applying pre-emergent crabgrass control can I...?

bvisailor

Comments (9)

grass1950

bvisailor

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