I'm intending to aerate and kill the moss in my garden in the next couple of weeks and wanted some advice on whether I should kill the moss and scarify the lawn first before I aerate it or doesn't it matter.
Vendée, Western France
I don't think so. Easier to get a fork or other prodding thingummy in to aerate when the ground is damp but no point in doing it when really wet as you'll just compact it. Read the instructions carefully before applying the moss killer as it is easy to overdose and then turn your entire lawn black and there's probably an optimum temperature too.
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
Conventional wisdom is to kill the moss first (iron sulphate), then scarify the lawn. This is on the basis that if you scarify when the moss is alive, you could spread it around your garden and make a bigger problem. Personally I'm not too worried about that: I have a lot of moss all over my small lawn, so I can't imagine making the problem worse. I prefer the idea of eliminating the bulk of the moss, then killing what's left over.
You don't want to scarify until the grass is growing strongly or else it will really suffer. I would be surprised if it's growing well enough by the end of the month to do this, especially with the cold weekend ahead. You could add some fertiliser now though (after the cold snap) to bring the grass along and get it in good shape before you scarify. When you come to scarify, make sure the lawn is dry and give it a close trim beforehand. This will limit the damage.
As for aerating, this just needs to be done when the ground is soft but not too wet. If we don't have too much rain by the end of the month the ground might be okay. I don't think it matters whether you aerate before or after scarifying. You might want to plant to overseed after scarifying though.