I have now tried washing the poinsettia's sour soil with warm dish detergent & water, then rinsed it. That didn't help. (Sorry. I didn't see the hydrogen peroxide post until now.) Then I left it to dry out. After a week, it was still soggy. So I lifted it out of its pot and let it sit out that way. After a few days, it was still very wet. So I poked several pencil holes all the way through the potting soil, being careful not to break any major roots. That worked! This morning I put it back into its plastic pot, but I haven't watered it yet. It seems to be a tiny bit wilted, but not bad. Shall I repot it while the soil is dry and easy to remove or shall I water it again? Lisa~

Watch out with terms- "sour soil" is normally used to refer to acidic soil (and your pH is great). OK- it smells sour after you tilled in grass clippings and leaves. My guess is about the same as kimmsr- the leaves, and grass are holding lots of moisture and creating anaerobic conditions. The wet soil, and maybe some matting of material, is limiting air to the site of composting. This is not as big an issue as you might imagine- many bury compostables and let them decompose in the bed with great results. If I was you- I'd stop tilling so much and let it do its thing. When the leaves and grass decompose and the soil dries a bit the soil will breathe a lot better. In the future- just adding that stuff mixed up and left on the surface will add all the goodies without the anaerobic decomp.

I use equal parts Turface (calcine clay), Poultry Grit (crushed granite) and Reptibark (fir bark fines). I'm in Zone 10a, S Florida and it works great. I've had rot in regular soil or even in a dry mix with some soil in in it. All you need for rot is a few cool, wet nights in a row. I fertilize with Dyna Gro products also. Poultry Grit and Reptibark can be bought online at Walmart.com and Chewy.com. I see Turface sold through 3rd party vendors on walmart.com and ebay. I bought it in person. It's comes in a large 50 lb bag and it looks like people are repackaging it into smaller bags and reselling it. I might do that because I bought too much. If you think you'll have a need for the 50 lb bag, the Turface website, turface.com, lists local retailers by zip code. I was able to find it at a local lawn supply store that way. It's an amazing product. My trees get almost all day sun in my south facing yard so I water a few times a week. YMMV.

I have not read even one comment here where someone has said that not recommending a soil test is 'the preferred course of action'. Just reread the thread (this, and/or the one on the other forum) and count how many times I have repeated that the responsible course of action IS to recommend a soil test. But, getting a soil test is not, in any way, a necessary action. What I have said is that it MAY be necessary, and it MAY NOT be necessary. I have also said that if anyone would like to learn the list of circumstances I proposed about when a soil test is a better choice than in other situations, then you'll find that list in the thread on the other forum. There's a difference between recommending the test, and making the person feel that a test is required or they are somehow doing something wrong. The test is simply better for certain situations (listed on the other thread.) And, a test is the only way to get exact numbers on any given sample of soil (and even that is just an average of the soil in any sizable area of ground.) It just seems that there is a rip tide of 'you must get a soil test before you can garden'. And this is absolute nonsense. Again though - for those who seem to be misreading the comments - recommending a soil test IS the responsible course of action. However, whether to get a professional test, or not, is a decision that entails more factors than just 'needing to get one'. In some areas of the country, a test from a professional lab can cost a LOT of money, and just finding the labs takes effort. If those who think everyone should get a test want to be precise, then they should preface their comments with good reasons that speak to the specific circumstances of the OP. This is one of those times where there is just not enough info given in the OP to be pushing the - 'you must get a professional soil test' - line.