Use pre-emergent weedkiller *and* reseed damaged areas -- how?

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I have combination fertilizer + Pre-emergent weedkiller ("Crab-grass preventer") that I bought *before* part of our lawn was dug up to replace a water pipe.
Now I have two conflicting requirements:
1. prevent all the crab-grass seeds from germinating
2. reseed the bare areas.
Will simply covering with plywood or plastic the areas I want to reseed while I am applying the fertilizer+weedkiller, *then* reseeding and fertilizing (with starter fertilizer) the bare areas work?
Any better suggestions?
Perce
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In belched:

what kind of grass? the typical weed and feed is BS, you're better off using a seperate pre-emergent and then buy the cheapeast fertilizer and add 1lb epson salt and 1lb sugar. Personally I have never had good luck with seeding except for fescue, I prefer sod, but then I'm in the south YMMV
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On 04/10/14 09:40 pm, ChairMan wrote:

I overseeded two falls ago with 40% Kentucky bluegrass, 60% perennial ryegrass, as recommended by local seed company. Still have some left.

The fertilizer + Pre-emergent weedkiller I have is the store brand, so even at regular price a lot cheaper than Scotts. And I got it on sale and with a further discount for using the store-issued credit card. About $25 for enough to cover 15,000 s.f.

What about digging up a few plugs of the existing lawn from inconspicuous places and planting the damaged areas with those?
Perce
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<1lb epson salt and 1lb sugar. > What is the epsom salts and sugar for???
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So your seeding for cooler northern climate? As long as ya keep it moist and can keep the birds from eating the seed, you should be okay

Well, at that price, what the hell. But from what I've read, been told and experienced, the weed and feed is useless. Are you sure its Pre-emergent weedkiller? Typically pre emergent doesn't kill weeds, it just keeps their seeds from germinating and needs to be used 2-3 times a year. A weed and feed usually needs to be applied when the grass is damp for the weed killer to stick to the weeds and kill them. If it's applied to a dry lawn the weed killer is useless.

You could try it. Bluegrass and rye are both clumping grasses, so it should work Good luck
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On 4/11/2014 1:03 AM, ChairMan wrote:

The best defense to crab grass is proper care....mow high in hot, dry weather, deep watering (1" per week if no rain). I bought pre-emergent for the first time this year (Scotts, against my better judgement). I bought the "Snap" stuff....just drop the bag of poison onto the rig and start rolling :o)

I use hose-end sprayer for broadleaf herbicides, once, and they do a great job....killed off most of the dandelions and others last year. It takes at least 2-3 years to take care of seed that is already in the lawn, but applying b.h. once, along with proper care, eliminates almost all b. weeds. Just spot treat after that. For tough weeds, like dand. and plantain, I sometimes use a brush with Roundup to kill 'em for sure without hitting the good grass.
I've used b.h. on southern and northern grass, and southern grass, like St. Augustine, requires it's own special product. You need to use them when weeds are actively growing and when the lawn is not stressed by heat. I fed the lawn a week or two before using it to maximize the "actively growing" part...it fun to see the weeds shrivelling up in a day or two :o)

shrub and flower beds to eliminate the dang mowing....I ran across an article that advised feeding grass FOUR TIMES A YEAR! Maybe for southern grass that has to grow in sand, but it guarantees you will be mowing a lot more...we feed ours mostly with a mulching mower, unless I need to bag grass clippings to use as mulch. My neighbor has big maple trees, so I rescued a lot of his leaves to use as mulch on my flower beds. I have "repurposed" a lot of stuff in planting/caring....plant a shrub, remove the largest rocks (we have a lot) and use the rock for mulch around some beds (with landscape cloth, of course).
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snipped-for-privacy@sbcglobal.net wrote:

epson is for nitrogen and sugar is for soil conditioner. Some areas of the country ya probably don't need the sugar, here in NTX with our gumbo/clay based soil it helps
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On 4/11/2014 1:03 AM, ChairMan wrote:

magnesium sulfate, and allegedly helps plants take up N. Sugar? I have never heard of using sugar for gardening.
http://www.garden.org/articles/articles.php?q=show&idh
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On 4/10/2014 9:32 PM, Percival P. Cassidy wrote:

It is too late for pre-emergent weed killer, unless you live pretty far north. Save that for next year (very early spring). Reseed the bare spot, concentrate on getting your lawn in good condition otherwise (proper mowing, watering, etc). If you have a lot of broadleaf weeds, treat them later in the spring, before weather gets hot and dry. Pre-emergents are the nastiest chemicals, so you don't want to waste it.
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On Friday, April 11, 2014 6:59:41 AM UTC-4, NorMinn wrote:

It depends on what weeds he's specifically trying to prevent from germinating. If it's crabgrass, which is what people are generally using pre-emergent for and most concerned about, it's not too late for much of the USA. It's been a cold Spring so far here in the NYC area, crabgrass takes warmer temps to germinate, but I'd get it down right away. There are also products like Dimension, which is a pre-emergent, but also provides post emergent control, ie it will kill early stage crabgrass too. No reason you can't put that down now in much of the USA.
There are pre-emergents that are compatible with new seeding, eg Tupersan, but it costs more than the typical pre-emergent and is harder to find. Depends on how big the re-seeded areas are. If they are small, just not-applying pre-emergent there is probably easiest, cheapest. Use starter fertilizer instead.
As to the claim someone else made, that only the products that are sold seperately for pre-emergent are effective, IDK what that is based on. A lot of them have the same chemical, combined products can be just as effective and certainly are easier to find.
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On 4/11/2014 8:33 AM, trader_4 wrote:

I think the pre-emergents are more toxic to aquatic critters and more persistent in soil. Broadleaf weeds are much easier to kill with herbicides that are less toxic and break down more quickly....lots of folks don't read labels and follow the "more is better" principle, which is why our waters are so polluted.
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On 4/11/2014 6:59 AM, Norminn wrote:

My rule of thumb is to get the pre-emergent down before forsythias bloom. Here in Northern DE its usually the first week of April. Areas of lawn that warm faster next to asphalt drive and road will germinate crab grass sooner and even earlier application is needed.
For OP, I'd put down pre-emergent right now and seed without starter fertilizer which is redundant.
Pre-emergent only works before crabgrass sprouts. Multiple applications are only necessary for weeds like Japanese stilt grass where seeds may sprout all season long.
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On Friday, April 11, 2014 8:33:46 AM UTC-4, Frank wrote:

The typical, common, pre-emergents that you find in a garden center, HD, Walmart, etc are not compatible with seeding. They will prevent the grass seed from germinating too. He can either:
A - Use typical pre-emergent on lawn areas that are not being seeded and and starter fertilizer in seeded areas, which is what he proposed
B - Use a pre-emergent like Tupersan that allows seeding.

That is true with the vast majority of them. But some, eg Dimension, are also effective against very young stage plants too. So, if you think it may be too late for a regular one, Dimension would be a good choice.
Multiple applications

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On 4/11/2014 9:27 AM, trader_4 wrote:

Yes. He's got the mix and we don't know what it is. For myself, I'm trying something different this year. It's a Spectricide weed stop product that they say can be put down at any time and is good for 5 months.
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On 4/11/2014 8:33 AM, Frank wrote:

I'm in northern Indiana, and it is too late here to be sure of best application. Because the stuff is so toxic, I feel it is wiser to hold off a year rather than spead the stuff around when it is too late to get best effect on weeds.

I'd be sure to follow directions, as seeding must be delayed for most p.e.h.'s. Reading labels helps!

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On Friday, April 11, 2014 9:41:15 AM UTC-4, NorMinn wrote:

Since you previously posted that you only used a pre-emergent one time, how would you know that it's too late to apply now for crabgrass control? There is a lot of conflicting data on when to apply. At most, northern Indiana should be near the end of the ideal time to apply, but not out of it. Especially since it's been a cold Spring so far. If you put it down too early, it can be losing it's effectiveness before crabgrass even germinates. For that area I would think first couple weeks in April is about right.

If it's delayed, it's pretty much delayed to Fall, unless you want to try seeding in summer.
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On 4/11/2014 10:49 AM, trader_4 wrote:

Other plants and weeds have sprouted....we had a blizzard 'bout three weeks ago, followed 2 or 3 days later by 50 degree daytime temp. It has been warm/cold alternating for a while. I think that if other weeds are coming up, the crabgrass is ready, too :o)
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On Friday, April 11, 2014 3:27:21 PM UTC-4, NorMinn wrote:

All plants and weeds don't germinate at the same time. Crabgrass needs soil temps consistently in the upper 50's to low 60's. That's why broadleaf weeds can be a problem in May/June, but crabgrass isn't a problem until Jul/Aug. Depending on where the OP is located, it could be too early, ideal, or too late for pre-emergent. Here in NYC area, it's about the right time right now.
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On 4/10/2014 7:32 PM, Percival P. Cassidy wrote:

Lawns are not one of my skills, but the weather the last 2 years damaged what was not a great lawn to start with (I have great weeds) and I did some research.
In Minneapolis the suggested period for pre-emergent herbicide application is May 5-20, on average. And we had a late spring. You might want to check at a competent garden center.
For grass seed here, may not apply elsewhere: Grass can be low maintenance or high maintenance. High maintenance presumably looks better, but needs more water and fertilizer.
The packaged grass seed mix you get at hardware/box/similar stores is "genetically improved", which means there is a patent (or whatever) that restricts the sale. "Improved" very likely means high maintenance.
Garden centers are likely to have seed mixes that have been around for a long time and are low maintenance. Likely sold bulk.
Depends on how much work you want to do.
(The package mix I got years ago also does not match the rest of the lawn.)
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On Friday, April 11, 2014 6:55:59 PM UTC-4, bud-- wrote:

I have to disagree with the last part. Improved can mean many things and it's most often not an indication of higher maintenance. There is a much bigger market for grass that is low maintenance for one thing, than one that is high maintenance. That's true in both the home and commercial markets, especially today with increasing restrictions on fertilizer use in many places. Some of the things that get improved are disease resistance, insect resistance, drought tolerance ie less watering, slower growing, better color, finer texture, quicker to green up in spring, better color over winter, etc. With any of those it's almost always a compromise. You can't get everything in one grass. But as an example, I'd sure take one of the many newer improved tall fescues over the older Kentucky 31. The new ones are much finer blades that look a lot better for a lawn. IMO, high maintenance usually goes along with having a showcase type lawn.
Anyone that is really interested in the ratings, there is a lot of data from the NTEP (national turf evaluation program) available on line. They rate many of the grasses in the above and more performance catagories at test sites across the USA. Using that can help you decide what's best for you in terms of your needs and priorities.

Around here garden centers have similar stuff to what's sold at the big box stores. If you want a specific grass, you can also find it online sometimes.

That's one potential problem with spot seeding. It helps if you at least know what kind of grass is there now as a start. If you seed a big bare spot in a bluegrass lawn with K31 tall fescue, you're probably going to notice it. Most people have no idea of what's there though.
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