I think that would depend on your weather. I would wait until at least Spring or when the sign of frost is far behind (Spring is the end of March, but for some it's still cold for another few weeks).
If it were me, I'd wait until about April, that would be warm enough and also give them enough time to produce roots long before Winter.
I don't know if growth hormone is a necessity, but if I remember correctly, it does have an anti-fungal in it so that would help keep them from rotting or developing something else before their roots produce and would also help with root production.
Planto
