Overseeded in Fall, weeds in spring, help?

lccraigMarch 27, 2012

My husband & I moved into our house in spring 2010 and didn't do much to the lawn at all. We are in SE Michigan.

Last fall we decided to overseed because the lawn was very patchy & had a ton of weeds. We aerated the lawn, dethatched and overseeded in September using a KBG, Fescue & Rye grass seed mix. We watered a lot & fertilized too.

Now here we are in March and the grass is still very patchy & we are starting to get a lot of weeds popping up. We can tell what is the new grass because it is much greener than the old grass. We just put down Scott's Turf builder with crabgrass preventer.

Should we put down a broadleaf weed preventer? Since we are in early spring is there a chance that the new grass will fill in and crowd out the weeds? What should we do to kill the weeds that are already growing? When should we put down some fertilizer? We are new to lawn care and are confused as to what we should do. We are planning to overseed again this fall. Any input is appreciated.

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dchall_san_antonio(8 San Antonio)

Yes you are somewhat confused. We can help.

The first fertilizer in the spring should go down after the second time you mow real grass, not weeds. If your grass is still patchy, then your early fertilizer is only fertilizing the weeds. However, the good news is that well fertilized weeds die better/faster than weeds in poor health. So, in 2 weeks you sweep in with a Weed-B-Gone spray and spot spray the remaining broadleaf weeds. If you have pictures of your weeds, that might make a difference as to which Weed-B-Gone product to choose. When you spray the weeds, you are not trying to drench the weeds and all the soil around them. All you need to do is mist the leaves of the weed. Beyond that you are wasting the product and hurting the soil biology.

Your lawn will soon leap out of the ground. By the time you mow for the second time, you might be mowing more than weekly. If that happens, you will not need to fertilize for a good long time...unless you really enjoy mowing. You likely can wait until Memorial Day to fertilize again. So far I'm only talking about Scott's type chemical fertilizers. If you want to use organic fertilizers, you can do that any time as much as you want without repercussions. Most of the organic ferts do not come with a huge growth spurt. It really depends on the health of your soil.

The weeds you have now are much like wild flowers. They will die off as the sun rises and the heat comes on. Your best defense against summer weeds is to restrict your watering and allow the soil surface to go completely dry before watering again. This time of year that can take a month. In the summer it is more like a week. The mantra for watering is 'deep and infrequent,' to simulate what Mother Nature does with rain. If you get an inch of rain, you don't need to water. If you get 1/4 inch of rain, then you need to apply 3/4 inch. By allowing the surface to dry out you will do many things. That will force the grass roots to dive deeper into the soil looking for moisture. This is a defense against drought. When a lawn is watered every day, all it has it tiny little roots that die in the heat. Infrequent watering also keeps new weed seeds from germinating. They need continual moisture to germinate. Infrequent watering is also a cure to thatch. When you water frequently you get a lot of build up of plant material right at the surface and right below. If you do this right you should not have thatch again.

Mowing: Set your mower for the second to highest setting. That's one notch down from the top. Tall grass does much better than short grass (unless you have centipede, bermuda or bentgrass). Tall grass is better in heat and helps shade any thin spots to stop weeds and keep the soil cooler.

Fertilize with chemical 3x per year. Once in the late spring and twice in the fall. Fertilize with organics any time as much as you can afford. My current favorite organic fertilizer is alfalfa pellets (sold as rabbit food). It's my favorite because of the cost and the amount of protein in it. Protein is the source of nitrogen but it is also a food for the microbes in the soil. They are going to do the fertilizing for you.

Here is a picture post here by mrmumbles from last year. He fertilized the spot with alfalfa in May and took the photo in June. Note the improved color, growth, and density. Grass type is zoysia.

Okay enough show and tell. Back to your lawn...the dark green grass you're seeing is the KBG. You're gonna love that. It is going to be the work horse of your lawn. Whenever there is a weak spot in the rest of the grass types, the KBG will fill it in. Pull some weeds and the KBG will fill. Rye and fescue grow in bunches and do not spread fast like KBG does.

    Bookmark   March 27, 2012 at 8:08PM
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Thanks for the response! I am going to try to attach a few pictures of the weeds we have. We mainly have dandelions. Should I put down a pre-emergent (green light?) or should I wait and spray each one after we put down a fertilizer like you mentioned? What do I do after we spray them, pull them or leave them?

    Bookmark   March 28, 2012 at 12:15PM
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brettn_10(4-5 Northern UT)


First, I would not wait to over-seed in the fall. That is what everyone suggests, but I think mid/late spring is better. They say wait till fall because of the weed issue, but as you'll see below that issue is very easily fixed with KBG. More important is moisture and temperature, which are much better in late spring, and you get rapid growth immediately after germination. KBG is the stuff that really makes your lawn look good and it is very slow to germinate; up to a month if temperature isn't right. So germination is more important than weed avoidance if you are just over-seeding.

Second, how did you over-seed? In my experience there is a pretty specific process to get KBG to grow quickly from seed. The easiest way is to use a slit seeder. A good slit seeder will get the seeds just to the correct depth and they will grow very rapidly if the soil temp is correct and moist.

The other method is to broadcast, but if you do this you will absolutely need the following steps or you won't get good growth. Either way, follow the steps below, but 6 & 7 only apply if you are broadcasting the seed.

1) Apply alfalfa pellets @ a rate of about 20lbs per 1,000 square feet about 3 weeks prior to seeding. I use rabbit feed that costs about $14/50lbs at the local feed store. Horse pellets are cheaper at about $9/50lbs. Unlike the horse pellets that are larger and 100% dried alfalfa, the rabbit pellets are smaller (so you can you a spreader) and they are only about 80% alfalfa. They also have molasses which will give your lawn a quick boost. Just make sure they don't have corn gluten meal as an ingredient since that is a pre-emergent and will stop your grass seed germination. After spreading the alfalfa, water it good and the pellets will plump and fall apart. Then drag a broom across them when dry to knock them down toward the soil.

2) Apply a light application of Quinclorac according to the manufacturer's direction 7-10 days prior to seeding. DO NOT OVERSEED WITHIN 7 DAYS OF APPLICATION!

3) Mow the lawn quite a bit shorter than usual just before seeding and bag the clippings.

4) Rough up the soil with either a thatch rake or a power rake. I prefer the latter, but you should rake up the thatch and dead grass if you used a power rake. This will expose the soil and open the surrounding grass to allow some light to the new seed.

5) Apply seed using a slit seeder (looks like a power rake or verticutter with a seed hopper on the back). If you don't use a slit seeder, you can broadcast the seed, but then you must also do the following steps 6 & 7.

6) Apply a light 1/8" or so of top soil. Don't worry about using "enriched" top soil or lawn soil that costs like $5/cf. Cheaper bagged soil can be had for around $2/cf or you can get it bulk for around $20/yard. But if you buy it bulk, inspect it first and make sure that it doesn't have a bunch of large bark mixed in with it. These will make your life difficult.

7) Rent a plastic water-fillable lawn roller and fill it only full enough that you don't have to really dig your feet in to pull it. Then roll down the entire lawn so that the new top soil is pressed down onto the seed. If the new topsoil is wet during this step you're gonna make a mess.

8) Add a light application of starter fertilizer if you want.

9) Water lightly 2-3 times a day extra, just to make sure that the soil stays moist.

10) If soil is moist (not waterlogged) and temp is consistently above 55-60 deg then you should see new grass starting after about 7-10 days. If you cut short enough before seeding, you shouldn't need to mow yet.

11) After another 10-14 days, your lawn will be getting a bit out of control and old grass will need to be cut. Set the mower on the second to highest setting and mow the grass gently, and bag the clippings. You do not want piles of clippings shading out the new growth.

12) Mow gently as needed (about 2/week) for another 28 days.

13) Apply Quinclorac again as directed. This should solve most of your weed problems. There are certain broad leaf weeds that quinclorac won't get, so if you have those, then use a product like Ortho Weed b Gone Max, which is a combination of quinclorac and 2,4-d and dicamba.

14) Apply rabbit pellets again every 4-6 weeks and reduce your watering schedule as the new growth thickens.

Stay on top of your mowing, never cutting more than 1/3 of the leaf off at a time, and you'll have the best looking lawn on the block.

P.S. Just my opinion, but I would use a straight KBG blend and avoid the fescue/rye seed blends unless your lot is very shaded. The good KBG blends like the "5 star KBG blend" from Arrow Seed is gonna give you a much deeper green, thicker, and softer lawn.

    Bookmark   March 28, 2012 at 5:09PM
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brettn_10(4-5 Northern UT)

I forgot one key point above. If water is expensive or limited in your area, DO NOT seed in the spring. New growth won't hold up to summer temps without adequate water.

    Bookmark   March 28, 2012 at 6:09PM
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Brettn wrote:

"First, I would not wait to over-seed in the fall. That is what everyone suggests, but I think mid/late spring is better. They say wait till fall because of the weed issue, but as you'll see below that issue is very easily fixed with KBG. More important is moisture and temperature, which are much better in late spring, and you get rapid growth immediately after germination. KBG is the stuff that really makes your lawn look good and it is very slow to germinate; up to a month if temperature isn't right. So germination is more important than weed avoidance if you are just over-seeding. "

Unfortunately this is incorrect. The best time to seed a cool season grass for most locations is late summer/early fall, not spring. There are a few rare exceptions such as places with extremely short growing seasons, but south eastern Michigan is not one of them. Also how is the weed issue fixed by seeding KBG? KBG is one of the longest to germinate and establish, and its spreading doesn't really start until it is about a year old. You do not get rapid growth immediately after germination. There are plenty of people with weeds in their established KBG yards. Soil temps are higher in late summer/early fall than in the spring, so germination will almost always be slower in spring. Another problem with spring seeded turf is that it is more susceptible to heat stress, and disease pressure during the summer. It will also use more water in the summer if there isn't enough rain.

    Bookmark   March 28, 2012 at 10:57PM
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brettn_10(4-5 Northern UT)

First, I acknowledged that it requires lots of water, so not to do it if water was either expensive or limited.

Second, I never said that weeds don't sprout. You're right, KBG is slow to fill in, so weeds do pop up. But there are a ton of selective herbicides for KBG. Weeds are very easy to get rid of with this type of grass.

Third, the OP is talking about overseeding, not starting a new lawn. Weeds are not any more/less of an issue regardless of when they overseed. If they were starting a new lawn it would be different, but when overseeding, there really isn't a reason to wait.

Fourth, when I said rapid growth I wasn't suggesting rapid like rye grass. If you wait until late fall when temps are at an acceptable 60-70 deg, then you only have about one month until temps are too cold for the grass to grow. You end up with small sprouts about an inch tall that don't start to grow vigorously until the following summer anyway. In my experience, planting in Apr isn't much different in this regard than planting in Sept.

But to each his own. I fully acknowledged that planting in late fall is recommended, but it should be stated that all the major seed distributors and agricultural colleges (like the one in my home town) recognize early/mid spring as a perfectly suitable environment for seeding KBG.

    Bookmark   March 29, 2012 at 12:23AM
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The bottom line is that the best time to seed, whether it be new lawn or overseed, is late summer/early fall. No one ever said late fall except you, and the acceptable temps you list are incorrect. While you can seed in spring with some success, it is not better than late summer/early fall, which any major seed distributor and or agricultural college will tell you. Another thing to remember is that this year is abnormally warm for the whole country. While this may allow for earlier germination in Michigan this year, an average year there would not allow for seeding until sometime in May when soil temperatures are above the threshold for cool season grass germination.

    Bookmark   March 29, 2012 at 1:21AM
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brettn_10(4-5 Northern UT)

Sorry, I should've said "ideal" 60-70 deg. Up to 80deg is considered acceptable, but when it is that hot you really have to stay on top of the watering. But maybe out there it is really humid. Out here, 80deg means watering very frequently just to keep the ground wet. Once the seeds have gotten wet, if they let them dry out then they are toast.

I also shouldn't have said late fall. I was thinking late Sept, which would be when temps are around 70F. In my experience, once the average daytime temp drops below 50, growth pretty much stops. That would be right around late Oct, and if they are like us, that is when everyone blows out their sprinklers for winter. Given the colder temps, full germination will be right around mid Oct, and by late Oct the new sprouts will be about 1" long. This means watering by hand for us, because even though it's cold, the new growth still needs to drink. IMO, that is really annoying, but I don't like to risk an early freeze damaging my sprinkler system. I don't have to worry about any of that when seeding in Apr.

But to your other point, you can still seed in Apr even if the temps aren't quite high enough. They'll start to germinate as soon as the soil gets above 50-ish. And if the lot isn't shaded, soil temps reach 50 before air temp does.

Anyway, I accept that Sept is the recommended "best" time to seed. My point is that early/mid spring is acceptable enough to go ahead and do it. If a person follows those steps, they will get perfectly acceptable results from a spring planting. I don't think there's any real compelling reason to wait until fall to overseed. Does it really matter if 20% fewer seeds germinate? Seed is really cheap and if a couple spots don't take, get them again in the fall.

    Bookmark   March 29, 2012 at 11:22AM
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dchall_san_antonio(8 San Antonio)

The OP said they were planning to overseed in the fall.

    Bookmark   March 29, 2012 at 3:52PM
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brettn_10(4-5 Northern UT)

Yeah, my point was just, why wait?

    Bookmark   March 29, 2012 at 4:22PM
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So I just happened to read your "blog" titled "Gross Lawn Rehab; fixing weeds, compaction, rodents, etc." I see that in summer of last year you were a complete lawn novice. I also see that you live in the high desert. Your area of the country has different rules for turfgrass. Your short growing season and dry conditions do in fact mean seeding timing is not typical with most of the country as I stated in my first post: "There are a few rare exceptions such as places with extremely short growing seasons". I appreciate your enthusiasm, but you have to realize that your limited experience doesn't apply to most of the areas that grow cool season grass. Your conclusion in that thread: "With KBG I'd do it in May if I had a choice. There are going to be weed problems whenever you expose fertile soil, but it is manageable. Forget about the weed issues because there is an easy solution there with KBG. But KBG takes a LONG time to come in from seed. The one thing that doesn't help is if it starts to get cold before it really starts growing well. IOW, if you wait till Sept to avoid some of the weeds and it starts to drop below 50*F in Oct, it'll be till late next spring before things start to look good again. The important issues with KBG are moisture and soil temp. May/June is best IMO. ", might be fine for your location, but remember, most people growing KBG have hot humid summers, and late summer into fall is a period of warm dry days and cool dry nights that generally last till November, which are the perfect conditions for starting cool season grasses. Soil temps are also optimal at that time.

P.S. If you haven't already done so, you really should add some gypsum to your soil.

    Bookmark   March 29, 2012 at 9:47PM
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brettn_10(4-5 Northern UT)

Fair enough. I'll readily admit that I'm a novice compared to you guys. I really wasn't trying to argue with you.

You are right too about my climate. It is too hot to seed here until late sept and then a switch is flipped and it gets cold really fast. By the end of Oct we are freezing at night.

Thanks for the gypsum suggestion and yes I did it last summer and also this year. I think between that and the organic fertilizer there has been a huge difference already.

    Bookmark   March 29, 2012 at 10:15PM
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I was really just looking for some advice on the weeds we have in our lawn, didn't mean to stir any debate, lol. We have already put down a crabgrass pre-emergent so seeding now is not an option anyway.

We are just planning on spraying the lawn with weed b gone for the dandelions and then will use the alfalfa pellets to fertilize.

I appreciate the feedback!

    Bookmark   March 30, 2012 at 1:39PM
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brettn_10(4-5 Northern UT)

I started the debate. My fault.

    Bookmark   March 31, 2012 at 12:08AM
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It's good to hear the differences of opinions... Reminds us that there is a very wide range of good growing for most turfgrasses....

I think if our OP was in Northern Michigan - I would agree that Spring is the right time to seed.... Even in Southern Michigan - the growing season is very short (Compared to here at least)... and that seed must be down when the heat breaks early/mid August... That planting window closes pretty quickly.... Miss that window and you start talking about waiting till Oct/Nov and Dormant seeding with snow covering the grass seed all winter...


    Bookmark   March 31, 2012 at 1:12AM
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