# KBG Lawn Thin due to Disease - seed or fertilize?



## Vetrano (Jun 12, 2020)

I am looking for advice on how to help my lawn recover and thicken up. My goal is for it to look substantially better by the end of this year and to be dense by next spring. My Kentucky Bluegrass lawn (sodded almost 5 weeks ago) went through leaf spot and melting out about 3 weeks after install. I'd estimate that I lost about 50% of the grass.

Am I better off seeding now and again in mid August or do I have enough surviving grass for it to fill in on its own if I do a nitrogen blitz?

The lawn in question is about 800 square feet near Toronto, Ontario. It gets a lot of shade from 2 maple trees and I have young children who play on it so it gets lots of traffic. I plan to irrigate through the summer as required.

I realize it is a little late for spring seeding, but given it is a relatively small area and I can irrigate throughout summer I am willing to seed now and again in mid-late August if seeding is the recommended approach.

The sod farm said they fertilized before harvest so I am planning to fertilize for the first time next week with Scotts starter fertilizer (24-24-4) that I have on hand unless I am convinced it is a bad idea to do so.

If I seed I am not sure what type to use. Should I stick with KBG or mix in perennial ryegrass or a fescue given my use and conditions? Before things went south I wanted to give the pure KBG lawn a chance in the shady area and figured I would overseed in the future with a shade tolerant grass if the KBG doesn't thrive. The only pure KBG seed I have been able to find is a coated seed by Speare Seed sold in 1kg bags, but they don't specify the specific cultivars of KBG. The description they give is "A low growing persistant fine-leafed variety species which produces a blue-green colour".

Any advice on how to proceed or products to use is appreaciated.


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## HoosierLawnGnome (Sep 28, 2017)

That will fill in this fall with proper encouragement and maintenance.

Another reason it could be thinning is all that shade. Shade can mean damp for longer too, which may be why you were more susceptible to fungus too.

Between the fence and big trees, that's hard to overcome without removing them.

So, look into shade cultural practices - more fertilization more frequently, letting it grow longer, etc.


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## greencare (Sep 14, 2019)

KBG doesn't fare well in the shade. I tried to seed one bare area unsuccessfully twice. It was originally KBG, but leaves end up there in the fall and winter, which just smothers it. But now, nearby KBG rhizomes seem to be spreading into that region, which I am pretty happy about. I spray the bare area every month with WeedBGon and that helps weeds/moss from spreading there.

Go ahead with the fertilizer. That lawn seems like it could use some. I also heard from 'How to with Doc's' YouTube channel that he puts extra fertilizer in shady region. I have yet to try this.


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## Vetrano (Jun 12, 2020)

I knew about mowing longer in the shade but the fertilizer part is new to me. I'll look into fetilizer practices for shade. If anyone can point me to any good articles it would be great. In general is the idea to provide more nitrogen than in the sun or is it to provide smaller amounts more often?

The thinning out occurred suddenly over a 1 week period. Between my aggressive watering and an unexpected rainstorm the grass was overwatered at the time to the point of being spongy to walk on. I noticed black spots and then more and more mushy yellow grass. I haven't watered in two weeks and soil is still moist at the surface. I am hoping it will dry out this week as it is sunny and getting hot. We are expecting rain in about 1 week so I will fertilize then as I don't want to add more water at this time.


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## HoosierLawnGnome (Sep 28, 2017)

Yes, apply more nitrogen in shaded areas. For me, it amounts to a few extra passes along the more shaded areas every now and then.

You probably suffocated the roots with too much water. I have the same problem where I get standing water.

I'd encourage with Nitrogen, increase the sun as much as you can, let it grow longer. With big trees nearby you may also have a lot of root competition, especially if maples.


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## Vetrano (Jun 12, 2020)

I'll try increased nitrogen in this area. I'm waiting for our next rainfall to apply fertilizer as I don't want to add water at this time. What is interesting is that this area dries out in the summer (my guess is due to the trees).

The tree roots were a problem in previous years, but before sodding I fixed some dips and grading issues which means the tree roots are burried a few inches lower (at least for now before they grow back to the surface).

I'm planning on pruning a few of the lower branches on the trees which may provide a marginal improvment in sunlight and air flow which I figure can't hurt.


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## Jackson (Sep 18, 2019)

Relax - slow down - your lawn isn't in bad shape for something kids play on and has a lot of traffic. It's going to look a lot better soon!

1. Put down 4 lbs (1.81 kg) of your Scott's Starter Fertilizer before this Friday evening (weigh it and set your spreader on a low setting and go back and forth and change patterns until it's all gone). That works out to 1.2 lbs / 1k sq/ft. Don't even water it in - you've got rain coming this weekend through early next week. Bonus but not necessary - it will help that water penetrate: if you have a tank sprayer or hose end sprayer apply 3 oz of plain original Palmolive dish soap. You can also drizzle it out of the bottle directly onto the lawn.

2. While you're poking around after spreading fertilizer this week - Get a ruler and set your lawnmower blade to a height of cut at or over 3.5 inches (9 cm).

3. Don't even think about mowing that yard until it's 9 cm tall, just leave it alone (don't spray for weeds, don't even cut/ pull those saplings) it's going to be a few weeks. It's perfectly fine for the kids to play on it, in fact I'd encorage you to break out the sprinkler as needed and let them play in it while it gets watered.

4. Do the same fert in late July right before a rain. Hit the blitz in the fall and you'll be really happy with the results not only this fall but next spring when it's growing like crazy.

That's it!


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## Vetrano (Jun 12, 2020)

Thanks everyone for the advice and @Jackson for the specific instructions.

The good news is that after 1.5 weeks of no water or rain the soil has finally started to dry out. The top 1/2" of soil was dry (everything beneath that is still wet to at least 6" deep).

I applied the Scotts starter fertilizer at the 1.2lbs N/1k sq ft rate as suggested. Our forecast changed and we are not expecting any rain for another couple days so I lightly watered it in since the lawn was starting to look like it could use some water.

Should I expect the grass to do any spreading during the heat of summer if fertilizer is applied and it is adequately watered? Or will it simply use the nitrogen to grow quicker?

I'm going to see if I can let the grass grow to about 5" before I cut it as high as my mower will allow, which is about 3.25".

I'm hopeful that the nitrogen will get the lawn back to good shape.


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## Vetrano (Jun 12, 2020)

Unfortunately the lawn has degraded lately. I don't see much leaf spot anymore so i think it is because our temperatures over the last 5 days or so have been in the high 80s to low 90s. The photos show the change from 11 days ago to today.

The top 0.5" of soil finally dried out on Friday after about 1.5 weeks of no rain, but it is still moist at least 6-8" under that. The grass that remained green did not exhibit any signs of drought stress (it remained green and soft), but some grass that was green a week ago is now yellow as can be seen in the photos. I can't tell if that is because it went dormant or died.

I did fertilize with the Scotts starter on Friday night and applied a little water. I also mowed today as some grass blades were approaching 7" (others were only 4-5").

Any thoughts or actions I should take at this time?

June 22:


June 11:


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## greencare (Sep 14, 2019)

How often are you mowing and at what height? I would give a week for the fertilize to work through the grass.


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## Vetrano (Jun 12, 2020)

I believe it was 7 days since the last mowing. I bagged the clippings and collected almost nothing. Height is 3.25"..


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## greencare (Sep 14, 2019)

Okay. Lets see how the lawn reacts to the fertilizer in a week. Do show the same area next Monday and make sure to water every other day as it is hot and dry.


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## gatorguy (Mar 13, 2020)

One thing to remember is that sod is grown on a wide open field with full sun. With significant shade, it should be over seeded in fall with a fescue - probably a shade tolerant tall fescue that has more tragidity than the weaker fine fescues if you have traffic on your lawn.


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## Vetrano (Jun 12, 2020)

@gatorguy, was "tragidity" supposed to be "rigidity"? If I understand correctly you are recommending that given the shade and traffic a shade tolerant tall fescue may be a good choice to overseed with? Are perenial ryegrasses a good choice?

Before I started this project I was anticipating the lawn to thin over time due to the shade and traffic, but I was hoping to give the kentucky bluegrass an honest chance to see if it can hold up with good maintenance (watering through the summer, fertilizing including a fall nitrogen blitz, etc). For now I'm thinking of sticking with this strategy and depending on the condition of the lawn late this fall or early next spring I will decide to overseed in both spring and fall of 2021 (and potentially every year if required). Luckily it is a relatively small area so this isn't too much of a hassle.


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## Green (Dec 24, 2017)

The main reason you might choose to seed KBG that is thinning like that, is to get new or better varieties in the lawn, for color, disease resistance, drought tolerance, shade tolerance, etc...if you have a specific issue to solve or just want to incorporate something better.

Otherwise, it's not so thin that it won't recover fully...fertilizing is the default option and should do the job..


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## gatorguy (Mar 13, 2020)

Vetrano said:


> @gatorguy, was "tragidity" supposed to be "rigidity"? If I understand correctly you are recommending that given the shade and traffic a shade tolerant tall fescue may be a good choice to overseed with? Are perenial ryegrasses a good choice?
> 
> Before I started this project I was anticipating the lawn to thin over time due to the shade and traffic, but I was hoping to give the kentucky bluegrass an honest chance to see if it can hold up with good maintenance (watering through the summer, fertilizing including a fall nitrogen blitz, etc). For now I'm thinking of sticking with this strategy and depending on the condition of the lawn late this fall or early next spring I will decide to overseed in both spring and fall of 2021 (and potentially every year if required). Luckily it is a relatively small area so this isn't too much of a hassle.


Yes.

With KBG and PRG its not that they arent wear tolerant...infact those are what are most commonly used in big sport fields with full sun. Its the shade factor though. If they arent getting enough sun and arent healthy and growing in thick then how can they be wear tolerant? Some of the new Tall fescues seem to be super wear tolerant and also do much better in part shade areas so if you arent trying to have a monostand then throwing some in the mix would probably help alot. I have PRG and KBG that grow in shady areas, but the difference in how weak, thin and lame those areas are compared to full sun is quite something.

Just a thought, good luck :smile:


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## Green (Dec 24, 2017)

Hey, @HoosierLawnGnome, I have never heard of fertilizing with more N in shaded areas. I've always read and if anything done the opposite, but that has generally been with Fescues in the mix. Is this a practice that's unique to KBG in shaded areas, especially the current shade tolerant (if you can call them that) varieties?

Another piece of advice I've read is to skew your fertilizer apps and seeding about a month earlier in shade...in conjunction with using less N.


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## Vetrano (Jun 12, 2020)

@Green I researched the use of extra fertilizer in the shade after the recommendations and the few references I found made the argument that the trees absorb a lot of the N so you overferilize to compensate for that. So it isn't really because of the shade, but rather due to the competition for the N from other plants (trees).


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## Green (Dec 24, 2017)

Vetrano said:


> @Green I researched the use of extra fertilizer in the shade after the recommendations and the few references I found made the argument that the trees absorb a lot of the N so you overferilize to compensate for that. So it isn't really because of the shade, but rather due to the competition for the N from other plants (trees).


That makes sense.


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## HoosierLawnGnome (Sep 28, 2017)

I would think foliar applied N in the shade would be even more effective than something that makes it to the soil and gets fought over.

That's my hypothesis though, no research for that


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## Vetrano (Jun 12, 2020)

I am contemplating options to handle approximately 150-200 square feet that is much more sparse than the photos I posted above. The photo at the bottom shows the largest sparse section.

Options:

Do nothing now and rely on the fall nitrogen blitz to fill it in. Is there enough KBG remaining for it to fill in this fall? I'm also worried that the bare spots will be taken over by weeds.
Overseed with annual ryegrass to provide some grass for my kids to play on and prevent weeds from taking over. My understanding is that it will not return next year as long as I don't let it seed by mowing regularly. I'm just not sure if this will inhibit the KBG from spreading when I do the nitrogen blitz?
Replace the most sparse sections of grass with new sod later this next week. I would hope that it will start spreading into the area I don't replace when I do the nitrogen blitz.

The options go from least to most cost as well effort, but I do want more grass growing there this summer. I'd like opinions on which option is the best and I'm open to other options which I may not have not thought of. I'd like to give KBG a chance in my shady lawn before seeding with a more shade tolerant type (all areas get some sun for at least part of the day).


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## g-man (Jun 15, 2017)

I would not use annual ryegrass. It is a weed in my opinion. Use regular perennial ryegrass. If there is a lot of shade, the area will struggle.


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## Jackson (Sep 18, 2019)

If 3.25 is your max cut, then that's the height you keep it. I wouldn't grow it to 5" and mow it back.

Your yard is fine from the update pics. It's still really really short & looks underfertlized. Hope it's up to 3.25" by now. As it gets longer, and healthier, it will 100% fill in.

If you are concerned about bluegrass in the shade - don't. 1. Mow it taller 2. Fertilize. I would not consider overseeing bluegrass with anything else.

Mow tall & fertilize and it will fill in.


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## Vetrano (Jun 12, 2020)

Since my last post on June 28 the lawn thinned out further in the "bad" areas (photos below). I fertilized the entire lawn with Scotts starter fertilizer on June 14 (1.2lbs N/k) and the colour has since improved, but it isn't growing quickly (due to heat).

I am confident that the "better" area will fill in this fall with a nitrogen blitz, but I decided to overseed the really thin areas on July 14. I know it is early to seed, but given the size of the area, amount of shade and the slightly cooler forecast I figured I'll try now and if it doesn't work I will overseed those areas again in mid August. This morning I saw lots of germination (I used a KBG/TTTF mix).

Now I am wondering when I should fertilize next. I am guessing I should wait at least 3 weeks from seed down to give the KBG a chance to germinate and then spoon feed to protect the new grass. I have scotts 27-0-2 and a 30-5-5 fast release fertilizer. Any suggestions on which to use, how much, when, and how frequent?


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## Jackson (Sep 18, 2019)

Your grass looks like it's an inch long. 3.5" grass is 350% longer. Which means it can capture 3.5x more sunlight, make more sugar to build bigger / deeper roots which will allow it spread and fill in. Once it's filled in it will choke out weeds and trap moisture from dew (my grass is soaking wet every morning), keeps water from running off and it will shade the soil so that moisture doesn't evaporate from the soil. The plant is also 3.5x as big so it can store more moisture so that it can make it through periods of intense heat with no additional water.



I spend minimal effort on my yard by design - I don't irrigate, spray weeds, use pre-emergent - I mow 1x a week and this has only had 1 dose of milorganite this year at bag rate either the last week of June or the first couple days of July and I shampooed it sometime in early June. This patch has 2 of my own kids playing everyday, and usually 2-4 of their friends, two dogs, bikes, balls, kids playing lacrosse / soccer. The back corner gets 0 sun all day and is just as thick as the rest. This lawn was mowed on Saturday and has probably grown an inch. The lawn actually looks better in person, much darker than photo (has that milorganite deep blue green) - but I didn't want to post an edited photo.


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## Vetrano (Jun 12, 2020)

Thanks @Jackson. If I can get my backyard as thick as yours I will be very happy.

I assure you the grass is not cut short. On the contrary, most of it is flopping over due to length. I think since it is so thin it has trouble standing straight up at longer heights.

Here's a photo from today that shows the blades folded over as well as the new seedlings.


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## Jackson (Sep 18, 2019)

Thanks for the photo. You are correct, the lawn will flop until it thickens up and the blades can support each other. You'll also notice that the good parts of your lawn will slowly spread towards the bad parts as it gets healthier.

I would say to hold off until you know the weather has broken - but - you've already jumped the gun. As long as you can stay on top of it and the weather cooperates I would start spoon feeding the 30-5-5 every 2 weeks once your sprouts hit 2 inches and continue until you run out of it. You are going to need to be very observant, start with a very low application rate (the minimum your spreader can effectively distribute) and work up to the sweet spot (less is more), in general you should see rapid growth. The 27-0-2 will take you through the blitz if you have enough of it.

You really don't see the full effect of the blitz if done correctly until next spring. All of that root development will page huge dividends.


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## johnr (Jul 13, 2020)

You may need a 'super phosphate" to stimulate root growth. HOWEVER, I would recommend a soil sample first to see if there is something else going on.


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## bernstem (Jan 16, 2018)

If you get less than 3-4 hours of direct sunlight, KBG is going to struggle. Longer grass, enough fertilizer, and maybe a soil test to look for other deficiencies will help with surviving in the shade, but if you can't get grass to grow that would make a nice garden area.


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## badtlc (Aug 22, 2019)

Vetrano said:


> I assure you the grass is not cut short. On the contrary, most of it is flopping over due to length. I think since it is so thin it has trouble standing straight up at longer heights.


I thought it was recommended with KBG to cut it shorter (<3") to promote more lateral growth and push it to fill in faster? This is a main reason I mow my yard at 2.25" or 2.75". If I get to 3" or more it thins out and falls over.


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## Vetrano (Jun 12, 2020)

badtlc said:


> I thought it was recommended with KBG to cut it shorter (<3") to promote more lateral growth and push it to fill in faster? This is a main reason I mow my yard at 2.25" or 2.75". If I get to 3" or more it thins out and falls over.


The recommendation for me to cut longer was due to the area being shady. I did however wonder if cutting shorter will be beneficial to promote spreading of the *** even though I have shade for most of the day.

Should I drop the height when I start the fall nitrogen blitz?


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## badtlc (Aug 22, 2019)

Vetrano said:


> The recommendation for me to cut longer was due to the area being shady. I did however wonder if cutting shorter will be beneficial to promote spreading of the *** even though I have shade for most of the day.
> 
> Should I drop the height when I start the fall nitrogen blitz?


I think everyone has their own method. I like to lower it just to help push the KBG to spread/thicken but I don't go super low. I Just drop one notch from 2.75" to 2.25"

I have some shady areas in my yard that I have overseeded with both TTTF and KBG. I don't know if it is my 2.75" HOC or what but to my shock and awe, the KBG is the only grass that seems to be thriving in my shady spots. It isn't super thick but it is green, lush and healthy. I think I need to follow the suggestions to provide extra fertilizer in my shady spots and see how it reacts. That might help it thicken.


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