Since you winterized, the only application in early to mid spring should be the pre-emergent--which goes when the forsythia bloom. I tend to fire a bit early when the forsythia just start to open their buds, but I'm also using a very long-lasting pre-emergent.

Really, most things off the shelf will do fine. I have a personal preference for Barricade (prodiamine), but Dimension is fine. Just make sure the length of coverage is enough to cover you through spring weed season and into crabgrass sprouting season (which technically lasts until temperatures start to drop in fall, but if you cover through summer that's fine).

While I use a rough calendar, it's only approximate and moves with the condition of the grass and the weather.

For synthetics, Memorial Day, Labor Day, October first, and winterize when growth stops.

For organics, step that back about a month, add another app on October first, and winterize with a synthetic when growth stops.

Thick healthy lawns with thick healthy roots should not be harassed by crabgrass much.
Since pre-emergents function by stifling root growth which kills the germinating seed; it also counters the Springtime root growth of mature plants. Working against the healthy growth of the grass always bothers me.
In Z4, applying pre-emergent chemicals can be put off until mid May most of the time, even though the forsythia blossoms appear in late April..

I used the generic version of Barricade (prodiamine) last year for the first time and was very pleased with the results. It was the WDG (water dispersable granules) type and application was easy with a pull behind sprayer. Price was not bad and I have enough product to treat my lawn for the next 5+ years.

Around here we tend to get rain at least every other day during prime crabgrass germination season so a pre m application is alway a good idea no matter how thick the turf is.

>>It was the WDG (water dispersable granules) type and application was easy with a pull behind sprayer.

It's also easy with a backpack sprayer. A hose-end can be managed if you're very even-handed and extremely careful.

Let us consider that Chicago is a cool season grass region and the ground may actually freeze during the Winter.
Mixing and matching Climate Zone Lawn Care Programs as though one size fits all, is not a good thing.

In the North crabgrass struggles in properly maintained turf and will not likely germinate at all, except in large spots of bare soil, excess water and unshaded soil.

Unnecessary root pruning is the larger principle here. :)

If root pruning is a concern, use one that is lower on the scale for that issue. Surfian would be flat out a bad idea for northern lawns in all circumstances, for instance, as it's strongly root pruning on northern grasses. Pendimethalin is low on the pruning scale, but does come with other issues. Tenacity has pre-emergent ability, but is expensive and only lasts a month or so.

In established lawns, the root pruning is modest for the approved pre-emergents for that grass type. On new sod, pre-emergent is never recommended (although there are one or two types that are fine).

Dimension, over-applied, can damage rye grass--but is OK for KBG. So proper dosing according to instructions is always important.

Like anything else, pre-emergent application is a balance of cost and reward. Given my P. annua problems, it's overall a reward in my case.

Around here root growth steps up in the Fall after a rough Summer, then again in the Spring as it first breaks dormancy.

I can't speak to P. annua as I've never dealt with it, only crab grass which germinates after the growth spurt is over and the soil warms up enough.

My concern is timing the root pruning to hit the soil just as the roots are digging deeper for the Summer. Once crab grass is no longer an issue, there is no reason to use it at all, but at least be kind to the growth spurt of Spring. :)

Thanks for all of the feedback everyone. I'm still relatively a novice when it comes to lawn care so please forgive me if I ask relatively obvious questions. What is root pruning? Right now my lawn is a blend of KBG, TTTF, and PR. I over seeded with KBG elite this past fall. I don't want to obviously harm my lawn with preem but also had a lot of weeds last year (mostly dandelions, crabgrass, and maybe even some p. annua). Would using Prodiamine be a good/safe solution here? Any thoughts on this one :

http://www.amazon.com/Prodiamine-Generic-Barricade-5lbs-ali8056/dp/B004GTQBEK/ref=cm_cr_pr_product_top#customerReviews

Root pruning is the slowing of root growth on lawns where pre-emergnents have been used. As the article I attached notes, it's not much of a concern on a reasonably healthy stand of grass.

That Prodiamine you linked to is the same stuff I use. It works well, has about 80-90% suppression, and hasn't caused a single visible problem in the lawn--or the gardens.

P. annua is a fall-sprouting weed, so spring application won't do much for it. I keep the layer up in spring and fall to combat it since P. annua is one of my issues. Tenacity is useful as a post-emergent herbicide, but does usually take two applications to kill the stuff.

Here is a link that might be useful: Root Pruning (plus other pre-M information)

Ok great. Thanks morph. The article was interesting too. Do you have any advice on how to use this stuff? Both application to the lawn and mixing?

It mixes into water very easily and it doesn't matter too much how much water you use to get it down. However, it should rain at least a quarter inch within a reasonable amount of time after application (or water it in) to get it off the soil surface and down to where it can do some good.

I've applied with a backpack sprayer (heavy but good, even coverage) and a hose end sprayer (light and easy, but you have to be careful to get even coverage). Both work out fine.

It is impossible for me to find real information on the web about what pre emergent herbicide functions and possible long term effects on turf.
I would think that using every year would generate a lot of surface growth as it prevents root from growing deeper every year.
Is the inclusion of a pre emergent going to be required for the rest of the lawns life?

If anyone comes across that kind of information I would enjoy seeing it. Thank You. :)

Seems like this would be a fairly easy study on a test plot. Would be nice to see results and resulting turf health and root density/length. I would think some university has tested it.

Now that i think of it, same goes for mowing height vs roots...

I've never found anything on root pruning either, which kind of leads me to think it's one of those things that Everybody Knows (and aren't actually all that significant). Consider--a pure pre-emergent can't kill a tiny weed once it's already sprouted, and the weed grows just fine (pre- and post-emergent chemistry mixed can kill it, of course). It leads me to think that any significant sensitivity is very limited to extremely tiny, young, and delicate plants.

One can certainly discontinue a pre-emergent when it's not required any longer. My mother no longer uses them as she no longer needs to--although we still hit her stone patios to keep weeds out of the cracks there.

>>>Consider--a pure pre-emergent can't kill a tiny weed once it's already sprouted, and the weed grows just fine (pre- and post-emergent chemistry mixed can kill it, of course). It leads me to think that any significant sensitivity is very limited to extremely tiny, young, and delicate plants.

One can certainly discontinue a pre-emergent when it's not required any longer.

I agree. Any harm to established turf is outweighed by ease of using a pre-m to clean up a problem lawn. Once your turf thickens, it will out-compete weeds and CG seedlings for nutrients and you can eliminate the pre-m and just use the occasional spot spray of a post-m.

I was not aware that the hormone that stifles root growth was not adequate to kill the germinated seed w/out the addition of other herbicides. Interesting concept.
Do we have any articles on that?

>>>I was not aware that the hormone that stifles root growth was not adequate to kill the germinated seed w/out the addition of other herbicides. Interesting concept.

I can't find where anyone has made that claim. Perhaps you have misinterpreted a statement?

>>>the germinated seed.
Sorry, missed the qualifier. You will find an explanation in nearly any article that addresses the differences between a pre-m and a post-m - timing of application and how the AI affect the plant.

Many pre-m only work if they are active in the soil prior to germination of the seed. They stop the seed at the point of germination and rooting. If the seed sprouts (greenery) and any amount of top growth is present prior to putting down Pre-m product... it is likely ineffective.

+1 BD and YT. Many say it right on the label to avoid disappointing customers.

Some have both pre-emergent and post-emergent ability, like Tenacity. Although primarily a post-emergent, it functions as a decent pre-M for about a month on some species.

I've had minor luck with some pre-Ms when applied to extremely young plants. But we're talking just barely sprouted and their deaths might have been incidental.

I find that with crabgrass if I am able to get a bit of milorganite down near time that crab starts sprouting (in troublespots) - that my bluegrass gets dark enough that it is super easy to spot the bright green crabgrass. Easy to pluck them out here and there while mowing or while walking the yard.

They pull right out with their thin spindly roots - they don't recover like other weeds when you miss some of the roots it seems.

Well, they don't recover until you spend a month ignoring them in a pot and they consequently have roots coming out the bottom. Pulling them at that point is not particularly helpful. :-)

Crabgrass is, fortunately, very easy to get rid of. It doesn't recover from mechanical removal when young, or even reasonably middle-aged. There's tons of chemistry that targets it. Frost kills it dead.

Really, on the list of Things to Worry About, crabgrass is pretty low down on it. No matter how bad it gets, it can be fixed.

P. trivialis, on the other hand. Ugh. Or creeping Charlie that's gone crazy.

Let's say you have a patch of lawn that is pretty heavy in crab grass and preemergents did not get it for whatever reason. If I pull the crab grass out I will be left with bare patches. Is it best to seed those patches even though it is spring? It seems to me better than leaving it as bare ground.

Let's say you have a patch of lawn that is pretty heavy in crab grass and preemergents did not get it for whatever reason. If I pull the crab grass out I will be left with bare patches. Is it best to seed those patches even though it is spring? It seems to me better than leaving it as bare ground.

Dealer's choice. If you can get the seed to take, and water over the summer, that's fine. And in smaller patches that's not too much of a burden.

If you rather (as I do) allow normal spreading to close the lawn, that's fine as well.

Now that my back lawn seems much healthier now than at the beginning of the season possibly it will fill in by itself in the high crab grass area. I did winter seed just in case as well.

It'll probably be fine, and you always have spring to decide it's not fine and do something then.

Yes, I practice the low-stress version of lawn care. Keep things in the groove as much as possible, correct what isn't, and don't get hysterical about it--it'll take care of itself for the most part if the soil chemistry and maintenance are there.

Winter seeding of Northern Grasses will germinate earlier in the Spring than will crab grass, because it responds in cooler soils temperatures than crab grass does.
I would put off pre-emergent till as late as possible to allow the all the seeds to germinate first.

Also I would add presoaked annual ryegrass in a tub of compost for the barespots left by weeding the crab grass.I may look funny early on but actually fits in a lot better than the CG or mud. This is especially true after a month or so.

Thanks for the tips, Maplerbirch!

A little bummed out I have to start my spring teen up by turning it white fighting poa triv. Since I have mostly TTTF lawn not much I can do besides killing it with round up. Extremely frustrating.

Sry ..... Meant to say Green up. Lol