All layers are started in spring, around the time the foliage has expanded and started to harden off. Exact timing varies from person to person, and I do not think it matters much. Earlier is good because you have a long growing season ahead. Downside: Rooting may be slower, as air temperature is low.

I do not use willow water, so can
t help you there.

Can you start a layering now in late summer and leave it until the following late summer or fall? What if you are layering branches in the ground near the original plant so it was a chancy it didn't freeze.

DhD

dhd47 wrote:

Can you start a layering now in late summer and leave it until the following late summer or fall? What if you are layering branches in the ground near the original plant so it was a chancy it didn't freeze.

DhD

Not sure what was not clear about:
"All layers are started in spring, around the time the foliage has expanded and started to harden off"

But:
End of summer, so almost autumn, leaves falling, less and eventually no transport of nutrients (or rather: hormones) to the air layer, no forming of roots, so I'd say: no, that's probably not a good idea.