Interesting article... about seed vs. sod. The Sod cost is about $800/1,000 sq ft installed with top soil. Not bad but not really in the budget... a near sure thing. For about 1/10 the cost, but more intensive management of seed germination, the seeds can be planted. The disruption due to rain I was not aware of or the fact about surface exposed seeds? These can be planted in the dry season, to avoid the seasonal torrential rains.

The term "topsoil" is meaningless because all that "topsoil" is is the top 4 to 6 inches of soil from someplace. Sandy soils, in Florida or anywhere else, tend to drain really well and they do not retain much soil moisture so unless the soil was amended well with organic matter, which will aid in moisture retention, your grass may not have enough water to grow. To root well grasses need 4 to 6 inches of a good soil, well endowed with organic matter, that is evenly moist but well drained.

It looks to me like the same grass but for some reason the spot in the middle is fertilized differently. Pick a side and apply organic fertilizer from the light green stuff, down through the middle of the darker green, and beyond about a foot. You can apply as much as you want. I'd say a couple double handfuls at least. Then water that enough to wash it down to the soil level and give it three weeks. If you have a dog or cat that eats dry food, use that to fertilize it. The ingredients in dry pet food are the same as in organic fertilizer, so I'm just trying to save you from asking what kind of organic fertilizer or having an excuse of not being able to find it. If you spill some on the grass, just brush it away a little. You cannot really overdo organics unless you smother the grass with it. That's the reason for using organics instead of synthetic fertilizer. Anyway I'm thinking/hoping the organically fertilized grass will all look the same in 3 weeks to a month. If it does then I suppose there are a couple reasons why that might have happened. All you would have to do ti fix it then is to fertilize the rest of the yard with organics. But this is a diagnostic test to see what the problem is. Oh, do you have a dog? It could be dog urine that caused the extra fertility in the spot. Where do you live? Why did you pick zoysia? The sod should be knit down to the soil by now, so it's time to back off on the watering frequency and start upping the amount. The target watering schedule is one inch applied once a week when temps are in the 90s. You should be able to get there in 6 weeks or so. By the time 6 weeks passes the temps might be in the 80s. The target in the 80s is one inch applied once every 2 weeks.

Sorry for the late reply. What we're doing is getting rid of the in-ground pool for the house we just moved into. But I met with the pool demo guy yesterday and it will probably be April 1st before he can start. So the sod I buy should be mostly out of dormancy by then, I would think. I planted Zoysia sod about 6 years ago and I really liked it. St. Augustine needs so much water and TLC. The place we just moved into does not have an irrigation system. That will be a challenge in the beginning, but once the sod is established I think I'll be better off with Zoysia, over St. Augustine. The area where I'm planting is almost full sun. So, long term, I think I'll have better luck with the Zoysia. The existing lawn is a mix; about 1/3 St. Augustine and the other 2/3's something else. The existing lawn is very healthy. Once it greens up I'm going to post pics of it. I'm curious what the "other" grass is. The soil in this yard is very good, by Florida standards. Thanks.