1) Pretty much it'll be sufficient. A lawn that was well-treated in spring and fall will certainly weather (hah!) summer much better.

2) Depends. Photosynthesis doesn't happen much over 88 degrees, although the plant can adjust its temperature by releasing water. Or other chemicals; some plants produce specialized chemicals that carry away far more heat than water does.

When the soil is dry, tossing away water isn't possible (or at least it's exceedingly unwise). So during cooler weather, grass can produce more carbs, and a cooler, wetter summer will certainly feature a ton of growth.

Hot weather really isn't much of an issue. The plants simply photosynthesizes in the morning and evening, skipping mid-day and afternoon.

Dry grasses tend to respond quickly to water, and usually recover in an hour or two. Well or poorly treated, that doesn't change much, although healthier grasses tend to have more root system and can absorb more water faster.

Severely shocked grasses may take some time to recover, but they'll do so if the watering remains consistent.

Dormant grasses are the slowest to recover (coming out of dormancy requires a large amount of energy and the grass usually doesn't have enough stored to play around with it). They're slower about it in hotter weather, and fairly quick in cooler weather (where water also doesn't evaporate quickly).

Strong grasses with plenty of energy storage will be faster, and less hesitant, about coming out of dormancy, but it's still not a fast process. The grass doesn't want to take the chance of recovering when the weather could turn dry again. That recovery was a waste of energy and could kill the plant.

So in a nutshell, a carb deficient lawn and a carb full lawn will both respond to watering during summer heat if left to dry out for whatever reason. But, the healthier lawn will naturally recover a bit better. Also, just a follow-up question, the carb store built up in the prior fall is carried through the summer and is not used up in spring growth?

>>But, the healthier lawn will naturally recover a bit better.

Yep. The healthier lawn is also likely to have a stronger, deeper root system as well, so it'll wilt later, shock later, and recover more easily just due to the greater root area.

>>Also, just a follow-up question, the carb store built up in the prior fall is carried through the summer and is not used up in spring growth?

For the most part, your lawn stores carbs very heavily in fall, which takes it through the winter and fuels spring growth. There's a second storage period in June when growth slows and the grass stores carbs a second time to carry it through the summer and fuel the regrowth in late summer to very early fall.

Are there some carbs left over from fall the following summer? Sure. The primary period of carb storage is fall, since it has to get through months of dormancy in winter using them. Summer's bad period usually isn't anywhere near that long, not for cool season grasses.

Potentially, anyway.

For a lawn that's armored in plate mail and discouraged from going into winter dormancy, carb levels will remain extraordinarily high all through winter (photosynthesis is slow and weak, but it does happen, and demands aren't high).

For lawns that are properly irrigated in summer and don't go into dormancy, the carb levels never get that tapped then, either. Demands are, similarly, lower in summer when growth slows, and that morning/evening photosynthesis is sufficient.

There's still no sense in feeding (cool season) lawns in winter or summer since they discard many of their fine feeder roots before the bad weather is going to hit. They take more energy to keep alive in poor conditions than they're worth, and the grass doesn't need them. They'll regrow either from stored carbs or from right-then-photosynthetically-produced carbs when the time is right, soil temperatures are moderate, and soil moisture is adequate.

OK, so I just learned something. The fall feeding gets the grass through the winter, using carbs even in dormancy (but presumably not when frozen solid). You've also reminded me of the root thing... If you don't get the carbs into the grass before it drops the fine roots, it makes it that much harder after they drop.

Maybe an odd question, but is there a way to determine the carb level in your grass? Can you actually see it in thicker roots, for example?

>>(but presumably not when frozen solid).

Even then! Frozen roots still have to stay alive, although the engine's running incredibly slowly at that point. Even in deep-frozen seeds, the clock is still ticking.

Fun fact: Seed banks and repositories store most of their seeds really, really cold (some of the Nordic countries do this in permafrost to reduce cooling costs to zero). Seeds can last centuries, but some do have to be replaced every few decades. I store mine in the (dry) cellar to slow the clock, but only require storage from August to October through February to April, depending on the species.

Even the best storage on lettuce seeds won't extend their lifespan past a single year. Some will sprout Year 2, but the percentage is severely reduced.

>>Maybe an odd question, but is there a way to determine the carb level in your grass? Can you actually see it in thicker roots, for example?

That's called a brix test, best done with grass sap and a refractometer. I would imagine that you can do it with the liquid in the root, but I can't say I've ever seen a process for it.

For those of us who don't have a refractometer, have bad eyes, or simply don't want to bother, the taste test can give you a faint guide Grass blades that taste sweeter are high in carbs and have a high brix. Grasses aren't exactly famous for their sweet flavor, however, and I doubt strongly you'll be able to tell the difference between a brix value of 2 or 3.

Indirectly, strong, upright growth and thicker roots imply a higher brix and an overall healthier plant (all else being equal). Healthier plants with all the proper amounts of resources are very efficient at synthesizing food. So as brix goes up, the plant has more opportunity to grow, and as it has healthy growth, the brix tends to go up.

Less indirectly, grasses that stay green during winter tend to have a high brix--sucrose is an anti-freeze, and although minor, helps a bit. I find that temperatures under 15° at night consistently mean that KBG is going to sleep regardless, it's just too cold for the poor things.