hey Erica, the backyard has pine trees surround the lawn like a border but the grass gets great sunlight, that moss area is where I stuck the sprinkler last year

Jon-

Where are you located?

Cool season grass? What kind? Late spring/summer is not a good time to seed. Early spring has come and gone. You best delay seeding until fall. You'd be surprised what some TLC does. Is this a new lawn or one that was pre-existing? If you've previously watered a ton, I probably would skip crabgrass pre-emergent and just deal with it as a post-emergent--your turf's root system is likely very shallow. Fertilization is best dealt with on a regional basis, so yes, it is important to know where you are.

Hey Joe, Mishmosh,

Good point, forgot to mention where we're located, east coast in Toronto, Canada, but basically same weather as Newyork.

Temperature throughout the day and night is about 40-70F and slowly rising.

Yes cool season grass, but I'm not exactly sure what kind, it was pre-existing, the house is 15 years old.

Thanks for helping us out.

I was about to go buy seeds and soil but I'll wait for advice from you all instead. Didn't realize it might be too late to seed.

Jon-

Definitely wait it out; you're not that far from getting started anyway......check out this thread:

https://www.gardenweb.com/discussions/4020257/j4c11s-fall-renovation-and-overseeding

He started the process in July, so you're only 2 months away.

I'm very familiar with the GTA. i think all you need is core aeration and fertilizer at this point. you undoubtedly have some spreading grasses such as Kentucky bluegrass which will fill in sparse areas. Most grasses do very poorly in soggy turf but as long as you have some grass present, it can make a full recovery.

never hurts to sneak in some weed-b-gone when no ones looking. lol.

@joe - that was a fun thread to read, thanks for sharing. JC in that thread chose to start this healing process in mid-July but I didn't find the reason of his timing. Given the condition of the grass (mostly like the first pic in thread), and where I am (east coast, Toronto), with weather right now being around 40F at night and 70F during the day, with showers throughout the week, which month should I be starting the same process JC took?

@mishmosh - ok cool this makes me at ease, I have the core aeration and fertilizers scheduled within the next 4 weeks

@shivece - just signed up to a lawn service, surprisingly not nearly as expensive as I thought given other type of contractors cost thousands even for small jobs in GTA. The challenge now is coordinating my own efforts with the lawn service because I found out that even the best lawn services in our area does things in batch, not tailored towards specific houses. They schedule things based on optimal business operations.

@charpell - makes sense, what's interesting is that no one in the neighborhood seem to water their lawn where I live, I never saw a sprinkler or manual watering, just cutting and fertilizers. Last year was the first time we were in the house so I thought it was just me not knowing what people normally do around here to keep the lawn healthy but this year I observed enough to see I was the oddball for sure

The problem with overseeding now is that seed germination requires frequent shallow watering. KBG in particular can take up to 3 weeks to germinate and is slow to establish after that. Meanwhile summer weeds are going to love all that shallow watering and your existing turf that has suffered from overwatering will not develop deep roots. Come summer, the seedlings will perish without frequent irrigation. It is really just not a good time to seed. Summer is the worst time but late spring is the second worst. Best time for you would be August, but like i said, hopefully it won't even come to that. Hopefully your lawn recovers.

there are also some patches (2 feet by 4 feet areas) where there's no grass at all from digging up so many dense weeds, thinking of maybe sod those patches and the rest wait until August for the rest of the healing process?

sounds good to me

Thanks everyone, will take all the advice and take this process seriously. Will post pics after it heals, prob many months from now. Really healthy and active community here on Houzz, super impressed. Homeownership started out stressful but starting to feel the satisfaction bit by bit.

I'm not sure how to get you to relax about this, but please try. As you learned with over watering, you can kill the lawn with kindness.

Filling dead weed spots with trimix (which I assume is topsoil, sand, and something else), is not critical at all. Getting good seed contact with the soil is the important part. You can simply walk on the seed and make that happen.

Growing grass in sand doesn't necessarily mean you have to water more frequently. Sand grains vary a lot. With coarse gravel you have to water frequently. With the Gulf coastal sands you don't have to water frequently at all.

I would use compost on the moldy soil and stop watering there completely until late August when you plant more seed.