Dhalias

Have decided to try and do things properly this year so have started two dhalias (Manhattan Island) off in a deep tray, not having a greenhouse they are on the windowsill in the kitchen.  Both are beginning to sprout, but how big do the new shoots have to be before they are put into the pots in the garden?  Does it depend on the weather, does it have to be warm before they go out?  Any help would be apprecialted.  Space on the windowsill is limited as I have seeds growing too.

They are not frost hardy- so cannot be planted out until May at the earliest-can you move them to a cooler spot to slow down growth a bit?

Or use the early shoots as cuttings to increase stock?

One of them has only one shoot which is quite long, if I take this as a cutting will it still spout again?  Should I have started them off later?

This is the problem if you have no half-way house-no cold frame either??

If you take that as cutting it should sprout again yes

Many thanks for your help Sotongeoff.  I will do as you suggest and hope for the best.