Hi Mark, 

Could you provide additional photos of the backyard site as a whole  (growth habit) and the patches that are in the browned out area as well? We can then refer them to our turf grass specialist so we have a better idea of how to help. 

It isn't the right time of year for Poa annua to flower so we aren't quite convinced that this specimen is that. It could be Poa trivialis which would be browned out by now and potentially that is what you had this spring. 

Let us know if you need help with the photos. 

Emily

I tried to upload pix last night and the website choked and dumped what I had uploaded and written in this space.... I will try again. In early April, the backyard was super green and beautiful. 

See IMG 2254. This is every early spring, backyard, looks great..... This was taken right after we mowed at 4-inch height on April 7. I am absolutely certain there was a sea of Poa A in this area prior to mowing. Seed tops everywhere...a lot. Of course not after mowing. Poa A was identified by a lawn care professional at this time. More and more every year, it's spreading like the weed it is. If it would not die and turn brown, it would blend in wonderfully with the fescue. Alas, when Poa A dies the entire yard goes with it as seen in IMG 2533. Very discouraging. Yes, I aerate and overseed with a TTTF tri-blend as recommended. There is so much dead thatch from the dead Poa I'll dethatch this year before overseeding, I have all the tools. I use a 24-0-5 weed/feed in the spring and fall. My pH is measured around 6.5 and I occasionally add dolcemite pellet lime. I have a pH measuring kit.  

I have other areas of my TTTF yard that do not get Poa A and they look very good. The front yard is wonderful right now and it gets similar sun as IMG 2533. ...as is a 1/2 day shade area near this really bad spot shown in IMG 2533. I will upload pictures of good-looking fescue that is not invaded by Poa A in a different part of this thread as I think maybe more than 2 of my pictures are too large for one writing. 

A thought....For the last 4 years I am using a mulching kit, not a bagger. I would hope that some of the Poa A seed tops would make their way into the bagger and not back onto the soil as in a mulching kit. Is this a good strategy for next spring if/when they return...? 

What I am looking for is advice from you on timing to put down any Pre-E products you may recommend to slow the germination of the Poa A in the fall and/or early spring. Obviously, the germination is dependent upon environmental conditions. Temperature, etc...

I am in central Calvert County. 

Here is a recent pic of A) IMG 2535 a small shaded section (50% of the day shade) of about 1000 square feet with very good fescue in the back yard within 25 yards of the dead brown in IMG 2533, and B) the front yard which is awesome...IMG 2532, which gets sun for virtually all day, 4000 square feet or more. 

So, my theory is ONLY that the areas where Poa A is abundant in spring look brown today. Cause/Effect?  

 it's not allowing IMG 2535 to post. It's green fescue in the shade :)

Hi Mark, I have forwarded your info and photos to our turf grass specialist to see what they recommend. We'll get back to you shortly. 

Emily

Hi Mark, 

We heard back from our turf specialist. He said these photos definitely look like Poa trivialis and also some tall fescue. The browning is heat and drought stress related. It could be from last summer as well as we have now had 2 summers in a row with little rain. If plants were stressed last summer and then headed into a drought again and high temperatures this summer it could have compromised the already weakened crowns.

His recommendation is to spot treat the areas of Poa triv. with a systemic herbicide next spring. One with glyphosate or triclopyr which will be non-selective and kill any turf grass around it but will help to target the roots. You can spot seed those areas as they die. Just be sure to read the label of the herbicide and make sure you wait the recommended time after application before trying to seed. 

This late summer/early fall about late August to Mid September, you should aerate and overseed the lawn with a high quality grass seed like you have been doing and be sure to water daily initially on days there isn't sufficient rain fall. Then as the seeds sprout you can lessen some as they mature and the weather starts to cool. He recommended doing this for a number of years to promote the desirable seed species. 

He didn't specially recommend a pre-emergent for this in the spring. One of those would be to primarily take care of crabgrass, stilt grass and other summer annual weeds. 

For the mulching mower and bagging- there are pros and cons. Yes on bagging and disposing because you would suspect that it would capture most of the seeds of the undesirable species. However, the benefits of leaving it to decompose on the lawn space is adding needed nitrogen back into the soil. It is also likely that the seed of the Poa triv. will travel regardless. So it would be up to you. 

Mowing higher at the 4 inches is recommended as well. 

So just keeping up with overseeding and trying to remove the Poa triv is the best you can do. Unfortunately Poa triv is so common and even in a lot of turf grass seed mix. 

Our new recommended grass species will be out in about mid-August, but what you have is still fine to use.

Let us know if you have further questions. 

Emily