I'm not sure what the purpose of scarifying the lawn is, unless you're planning to seed. Seeding is usually best done in the fall unless you have warm season grass. You can generally aerate when it's not too hot out and the grass is actively growing (so it can readily recover). You should be able to fertilize if the grass is green. If you've got cool season grasses, it's best not to fertilize in the summer because that encourages growth when you don't want as much growth. Do you know what kind of grass you have? Different kinds of grass have different fertilizer requirements. In the US, Kentucky bluegrass is the most prevalent cool season grass, and it should get about 3-4 lbs of N per 1000 sq ft per year. Fine fescues need much less than that.

What you might be seeing is thatch, old dead grass that is acting as a mulch and will be feeding the Soil Food Web. Some, 1/2 inch, of thatch is not a problem, but much more can be. When you mow do you collect the grass clippings or do you mulch mow?

Could be a hungry patch of ground. Rosette plants often arrive when the grass cover is sparse. You can rake over the existing grass with the sort of rake you would use for levelling tilled ground - not a leaf rake as it doesn't have enough weight to remove the thatching. Next: decide what sort of grass you think you'd like there. Remember that those pristine weed-free stretches of turf take a LOT of time, money and effort to stay that way - not to mention equipment. If you love lawns, though, why not? Lawns need good sunlight, though there are grass species that will grow in semi-shade, and your garden centre can probably provide you with a blend to suit. First off - dig out, or flame, or solarise, or poison those broadleaf weeds. If some of them are daisies, you have an acidic soil and may need to apply lime a few weeks before adding any fertiliser. You need to feed the area, and perhaps aerate. Lawns tend to have compacted soils below the sward. Feed means applying a layer of either topsoil or compost, then levelling and gently firming it (use a traditional roller if you can hire one, board or even thick cardboard which you walk over to firm up the seed bed but not squash all the air out of the soil). Lightly apply some general purpose fertiliser with a higher nitrogen level and rake it through the topsoil before you firm it. (Ask at the seed shop.) Use a couple of sticks to make fairly big 'squares' so you spread your fertiliser evenly. Drifts and bare patches don't work too well, and it can happen if you simply broadcast your fertiliser. Even if rain is forecast, water the area once the seed is sown - and do whatever you have to to keep off the birds and cats. This is probably a task for early autumn now. Once your new grass is established and has real leaves, sturdy little darkish green ones, not spring green, then be sure your lawn mower blades are sharp and set to about 2.5cm/1". Lightly cut. This helps to dissuade grass from forming clumps or tufts. You want it to spread out, instead. Cutting it to around 2.5cm helps to shade the roots, keep the soil moist, and discourage the arrival of weed species. While the new grass is young - remove any broadleaf seedlings as soon as you notice them. Dandelions can be particularly pesky if not removed when young.

I'm a fan of letting nature take its course with: 1) A lot of help and 2) Trying to mimic what nature does just not at nature's speed. And I'm going to disagree back again. " Whatever woody or barky particles that may be present in compost (and you DO want them) " You don't want them if you're digging it in. If it's compost, it should be fully decayed and particles shouldn't be woody or bark-like. If they're recognizable as woody or bark-like, they're high in carbon and absolutely will suck nitrogen from any source they can get it to decay. That's going to be a problem, from very minor to very major, depending on the amount added. I've seen that too many times to count. It can be countered--and small amounts added may be unnoticeable--but grasses grown on it won't perform very well until the nitrogen balance catches up. Consider. Nature rarely adds wood directly to deep soils. She lets it rot up top and then the worms and beetles and termites drag the rotten bits down under. Often as poo. When things get buried unrotted, they sometimes don't decay...and turn into fossilized wood. Or fossils. It's rare, but that's the start of things. However, if it's fully decayed compost, smells like fresh earth, and has no recognizable bits and pieces, it can be dug into the soil--at amounts up to about five percent. With one warning---it is going to decay off to nothing within a maximum period of five years. Which means the soil is going to settle. Which means if you got everything nice and flat, it's going to drop into a divot within five years. Maximum. More if it's a nice environment. The rules change for adding stuff up top. You want to chop up wood and toss it up there? Go for it. Sawdust? Have at it, I do (I find Equine Pine pellets to be an occasional nice addition). At the air/soil interface, anything goes. The only restrictions are for things that are dug down into the soil. Some meals also work wonders at transforming soils. Cracked corn offers highly fibrous structure with modest nitrogen, and a mild anti-fungal boost to boot. It's one of the best combined boosts for feeding, soil, and protection out there. Plus I've been maintaining and improving soil structure quite beautifully just on soybean meal as the worms also rather like the stuff, reproduce quite well on it, and themselves do the work. Personally, I wouldn't rototill. It's very hard to get a flat surface after doing so without calling a professional to box-blade. I didn't when the back patio and gardens were installed and I had trucks going back and forth. I should have sprayed shampoo (or my own sodium lauryl sulfate concoction) but it was before Andy and I had developed the formula in a late-night creative chemistry session. I fed the area heavily and frequently with organic food, as well as the surrounding areas, and within two years the problem had corrected itself--worms and other critters from microbial to very macro had fixed it for me. It's completely indistinguishable from the rest of the lawn. One thing you certainly could do is rent or borrow an aerator and aerate the area several times over. Generally, it's done 2 to 3 times, but for compacted earth, I'd do it 5 to 7 times. Really tear it up. There's no reason to load food into the soil at that time or before seeding unless you want to feed any weeds that grow and losing nitrogen to the air and water. Without knowing what your soil is like or what it requires, you're blindly dumping resources, which isn't environmentally sound anyway. You could get a test through Logan Labs if you like. Then, wait for temperatures to fall off their high. For you, that's like July 7th. :-) (More like August 10th or so, just when you look out and notice in the evenings that summer is just starting to come to an end and the tree leaves are looking a bit tired). Seed at that point. Feed with a good organic feeding (I'd suggest Milorganite or Ringers or soybean meal or really, whatever you can get) then too. Search around for how to start a new lawn patch or ask at that time because everybody else will be as well, and we've gone through it a ton of times as well. :-)