# Fall Seeding and Pre-em?



## behemyth (Jun 8, 2019)

I've been waiting all summer for it to be almost August, as now i can start seeing my weed infested backyard. Half of the seed that got put down when i bought my house took, so I still have bare dirt patches. That being said, this summer the weeds really grew in. I have a lot of weeds with purple-ish stems.

Should I seed, or should I use something like Tenacity, and kill the weeds off? I've read you don't want to use both around the same time. I _suppose_ I could spot treat them with roundup or something, I have a 4gal sprayer backpack so i could get the concentrate and then go to town. That would also probably not be good while growing new grass tho....

The sod out front is looking good, minus the few spots that are a really light brown. I think this is due to my irrigation being kind of spotty (have a company coming out to look at it). I'm also going to hit the sod with some kind of high N fertilizer here in a week or two, so it greens up and grows good before it gets too cold out.


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## social port (Jun 19, 2017)

you want to kill the weeds now with post-emergent herbicide. You need to be careful to not spray your existing grass now, as you could injure or kill it, even with herbicides that are normally safe for cool season turf.

Have a target seeding date in mind before you spray; that way you know when you can safely apply your post-emergent so that it won't affect seeding. Many post-emergents recommend waiting between 7-30 days before seeding. That is not the case with glyphosate (fyi...you could get away with same-day app if you really wanted to be adventurous).

Once your new grass is established, you might have time to get a pre-emergent down (check labels for prodiamine and dythiopyr). You can use tenacity when seeding bare areas, but I wouldn't expect a post-emergent response if you are using granular. And I wouldn't use tenacity as a primary pre-emergent -- only for a pre-emergent when seeding bare areas.


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## g-man (Jun 15, 2017)

I think the best course of action will be to remove most of the weeds and overseed.

You can do this with foliar tenacity (add nis) now to kill a lot of the weeds. Around the second week of August, throw more seed down. Since I think it is fairly bare, you can use KBG. The day you apply seed, also do tenacity at 4oz/acre rate for to the soil (no nis). Keep the soil moist and fertilize.

Next year it is a must to do a prem in the spring. There are still plenty of weed seeds ready to show up.


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## MassHole (Jun 27, 2018)

g-man said:


> The day you apply seed, also do tenacity at 4oz/acre rate for to the soil (no nis). Keep the soil moist and fertilize.


Does skipping the NIS just a cost saving measure, since there's no foliar action? Or a different reason?


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## ken-n-nancy (Jul 25, 2017)

MassHole said:


> g-man said:
> 
> 
> > The day you apply seed, also do tenacity at 4oz/acre rate for to the soil (no nis). Keep the soil moist and fertilize.
> ...


The purpose of a Non-Ionic Surfactant (NIS) is to increase the amount of the associated product which is absorbed into the leaf surfaces of a plant to which the product is being applied. This is also known as a "foliar application" because it gets into the plants via the foliage (leaves). The way that NIS works is it causes the water to have reduced surface tension. This reduces the ability of the water to "bead up" and form individual droplets on the surface of the leaf of the plant, but encourages it to instead spread out over the plant like a "sheet of water." By spreading the water out over the surface of the plant instead of having it bead up, more water is held on the surface of the plant (instead of running off the plant into the ground). There is also more surface area of the plant covered by the water/product so more of the water/product is absorbed into the plant.

So, basically, you use NIS when you want a sprayed product to get into the leaf surface.

If, however, what you want is for the product to get down into the soil, you do NOT want to use NIS, as you want the water/product to run off the leaves and drip down into the soil.

So, for a product which you want to get absorbed into the leaves, such as most post-emergent herbicides like 2,4-D or triclopyr, you want to use an NIS to help the product get into the leaves and have as little as possible run off into the soil.

For a product you want to get down into the soil, such as a pre-emergent application of prodiamine or dithiopyr, you would NOT use an NIS, so that the product doesn't just remain on the leaves of the plant, but runs off to get into the soil.

Tenacity (mesotrione) is a bit of a unique case, in that it is kind of a "dual use" product that has effectiveness as a post-emergent herbicide (whitens and kills weeds) when applied in a foliar application, and also has effectiveness as a pre-emergent (disrupts the germination and initial growth of seeds/seedlings) when applied to the soil.

So, if you want to allow the Tenacity (mesotrione) to get into the soil as a pre-emergent, it is important to NOT use an NIS, in order to maximize the amount of product which gets down into the soil.

If, however, the purpose of the Tenacity (mesotrione) application is to kill already-germinated weeds, you would use it with an NIS, so that most of the product gets in to the leaves instead of running off and ending up in the soil.

This situation is part of why most products which are sprayed but are intended to get into the soil are typically also "watered in" lightly after application. The light watering washes the product off of the leaves and gets it down into the soil. Of course, such a watering should be a light one -- the intent is to just wash the product off the leaves into the soil -- too much watering would not just wash the product off the leaves and into the soil, but will cause either surface runoff (which carries some of the product away, effectively wasting it and polluting the environment) or will cause leaching of the product into the groundwater (which also effectively wastes it and pollutes the environment in a different way).

Sorry for the long-winded answer, but I had a few moments, so I thought it would be more appropriate to "teach a man to fish."


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## MassHole (Jun 27, 2018)

ken-n-nancy said:


> This situation is part of why most products which are sprayed but are intended to get into the soil are typically also "watered in" lightly after application. The light watering washes the product off of the leaves and gets it down into the soil. Of course, such a watering should be a light one -- the intent is to just wash the product off the leaves into the soil -- too much watering would not just wash the product off the leaves and into the soil, but will cause either surface runoff (which carries some of the product away, effectively wasting it and polluting the environment) or will cause leaching of the product into the groundwater (which also effectively wastes it and pollutes the environment in a different way).
> 
> Sorry for the long-winded answer, but I had a few moments, so I thought it would be more appropriate to "teach a man to fish."


Great info! Thanks!


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## behemyth (Jun 8, 2019)

@g-man I discovered they use the Black Beauty strand of Tall Fescue for my sod, I was going to just get the seed version of that and start putting it down in back. You think KBG would be better off?


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## g-man (Jun 15, 2017)

I think a cool season mix lawn will benefit from some kbg in it for the self repair. Did they use only tttf?


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## behemyth (Jun 8, 2019)

Yeah, they left the label on the sod that my neighbor got, and its pure black beauty. It's the same sod we all have.

I'm kind of annoyed with it, because even though my irrigation is keeping it well watered, I still have light browning around the yard. Not really in patches, but some of the grass is turning brown and dying.

I can take a rake and rake it out, but my front yard is so big thats way more work then its worth right now. I plan on over seeding it here soon, but I'm debating what i wanna use. I was just going to use some tall fescue mix, but now that i know its a certain strand idk what to do. Pondering that now.


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## john5246 (Jul 21, 2019)

behemyth said:


> Yeah, they left the label on the sod that my neighbor got, and its pure black beauty. It's the same sod we all have.
> 
> I'm kind of annoyed with it, because even though my irrigation is keeping it well watered, I still have light browning around the yard. Not really in patches, but some of the grass is turning brown and dying.
> 
> I can take a rake and rake it out, but my front yard is so big thats way more work then its worth right now. I plan on over seeding it here soon, but I'm debating what i wanna use. I was just going to use some tall fescue mix, but now that i know its a certain strand idk what to do. Pondering that now.


if you know it's black beauty just stick with that. Mixing too many kinds of grasses causes it to look strange, they can grow at different rates and might have different darkness 
most people don't know what they have they just throw down whatever seed mix is cheap at the local big box store


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## behemyth (Jun 8, 2019)

@john5246 OK thanks. The place that sells it is right down from where i work, they grow the sod and sell the seed there, so I'm going to get a big bag of it, and over seed the front and get it down in the back. The entire yard should look good in a year or two.

I am worried that the light brown spots are actually being caused by rocks under the sod that the sod company never ever gets rid of. They just use a giant machine to grade the yard, leave all the rocks there, and just put sod down over it. Very frustrating. I have a feeling I'm going to have to rent a machine, cut the sod back up, get as much of the rock as i can, and then put it back down next spring.


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## behemyth (Jun 8, 2019)

@g-man Here's what the back yard currently looks like:

As you can see, lots of weeds growing in...


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## g-man (Jun 15, 2017)

I don't see just tttf. Tenacity should take care of those weeds.


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## behemyth (Jun 8, 2019)

OK cool. You think using Black Beauty in the backyard going forward would be a smart move? I want it to look as close to the front as I can get it.


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## behemyth (Jun 8, 2019)

Finally got tenacity and some NIS ordered. Got some blue marker from them too so I don't over spray and turn my whole back yard white.

I'm curious to see if the grass they put down in back is going to die off when I spray. If so, I'll just reseed the whole thing.


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## behemyth (Jun 8, 2019)

Got my first app of Tenacity down. Used NIS with it. Used a blue marker with it, that helped a lot with keeping in straight lines and not over lapping much. Guess we'll see how it does in the next few weeks.


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## behemyth (Jun 8, 2019)

So i applied some tenacity almost a week ago. Definitely working on some of the less thick weeds, but the barnyard grass looks almost unfazed. I guess its possible its a little lighter, but definitely no white on it like some of the other weeds. Gunna give it another week and then spray again if things don't improve.

app rate as .5tsp per 1gal water, with 1.5tsp of NIS per 1k sq/ft.


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## g-man (Jun 15, 2017)

I dont recall tenacity being effective against barnyard grass. Round up is.


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## behemyth (Jun 8, 2019)

You think the only way I can get rid of it is spot spray with roundup?

You were right, the backyard isn't just tttf. It's filling in and I haven't seeded it yet. Means whatever they put down has some kind of rhizone.

Think kbg would be best to fill it in? Gunna look kind of stupid compared to my sod out front that's pure tttf. That's going to really annoy me.


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## g-man (Jun 15, 2017)

You will thank me later if you apply some kbg.

Fyi, there area other grass that spread. Creeping red fescue is an example, but you don't want it I your yard. It doesn't like sun heat and turns brown.

You can hand pull barnyard grass. Maybe acclaim controls it, i don't remember.


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## behemyth (Jun 8, 2019)

Ok, I'll get some KBG down and get another application of Tenacity down, this time for pre-emergent. Maybe i could get my entire backyard to fill in with KBG, that would look good..

Like i said, just going to annoy me having two different grasses in the back and front, its going to look dumb where they come together on the sides of the house.


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