You might be fine on the overseed, you git good cultivars in that mix, its amazing you can do the work at 81

 

Depends on how you treat/push it. I installed ST so that I wouldn't need to worry about watering and it wouldn't require as much input. 2nd full season it started to get really thick even with low input.

 

Grass has a life span. The older it gets, the less quickly it grows and recovers. By constantly adding new young grass to the lawn, you ensure the lawn is always filled out. KBG can self-recover because it spreads via rhizomes. TTTF/PRG do not. In nature, these would not be mowed and would grow and drop seeds to reproduce over time.

I would not consider Super Turf II's TTTF as Rhizomatous. It is more of an "LS" (Lateral Spread), meaning it fills out nicely with tillers. The KBG will slowly spread over time.

Will you need to over-seed yearly? It depends on how you maintain/feed it, the heat, rain/watering, disease, and pests that could affect it. If well maintained, you could skip over-seeding for a year or two. If not well maintained, then you should whenever you have die-off or noticeable thinning. It is a good idea to overseed yearly as needed as the grass seed bank will ensure any opportunistic growth (in a thin or available area) gets re-populated.

 

Thank you both for the advice.

I tend to mow, water, fertilize, spray, manually aerate, and fuss over my lawn often enough to make my neighbors think I'm odd; the recent complete renovation thoroughly convinced them of it.

Having my own scarifier/dethatcher does take much of the work out of lawn care---except for setting up all the hoses, timers, and sprinklers.

Would it make more sense to overseed with the same Super Turf II... or go with Super Turf I -- without the Kentucky Bluegrass in the mix?

 

There is always some summer loss with TTTF/KBG. I am on my third reno with it, doing smaller sections of my yard. Despite abundant rainfall, though still periods of drought, I needed to rake an area out of some brown grass. More a function of soil temperature. Didn't need to overseed, just needed water and cooler temps. One small area had noticeable loss, and I did throw down more seed. Its all in my journals.

 

I have hever heard of grass slowing down with age. Is this based on anything scientific?

 

There was limited research on this that I can recall. The overall summary was a study on the age/lifespan of grass. It was found that the older the grass (in cases up to 30+ years of the same grass/crown), the lower the survival rate was lower. I think an assumption was due to the grass not being able to re-grow fast enough to survive damage.

The article below doesn't directly discuss the reasons for the survival rates but does report on the observed survival of plants and grasses.
Demography of perennial grassland plants: survival, life expectancy and life span - Lauenroth - 2008 - Journal of Ecology - Wiley Online Library

 

I recently did a heavy overseed partial Reno with ST2 as well 6a. Came in a bit slow. But really took off and filled in once mowed and the *** started to thrive. I’m glad I didn’t seed in bare areas. Took about 6 weeks to fill in 85%. She’s good now.

I’ll overseed if need be. But just keep up with fert mowing amd you might not have to this coming year. I’m impressed with this mix so far. Summer will tell though