So, I've been messing with air layering for a bit, and here's what I've figured out from my trials (and errors, oh so many errors). Did a few Japanese maples (Acer palmatum) here in my backyard. There's something about starting in spring that really works. I tried it last May, when the sap's flowing and the tree's in growth mode. It just seems like the trees are more willing to cooperate when it's warming up, and the risk of cold snaps is behind ya. But, if you wait too long into summer, the heat can dry out those layers way too fast, which happened to me with a pine once — that was the end of that experiment.

I normally use the sphagnum moss method; it's like wrapping a little hug around the branch. I soak the moss in water first, then make sure it's squeezed out before packing it around the branch. Holding all that together with plastic wrap and a twist tie is my go-to. It's a bit of a juggling act, for sure. One thing I learned the hard way: you gotta keep checking that the moss stays moist. I got lazy with one of my layers last year and by mid-June, it was toast. But, when it works, it's like magic seeing those roots peek out. Maybe other folks have other times that work, but for my maples, hitting that sweet spot in May was key.