BobbyLane
Imperial Masterpiece
It all depends on the local climate and what species - also the size, location and species you want to collect . You could wait till early spring but here in UK most commercial tree nurseries start lifting their bare root deciduous field grown trees starting in late October onwards and if theyre not being planted on a landscape scheme immediately their roots are packed with damp straw , bagged then stored in a cold shed in bundles till planting time, Alternatively dig a trench and heel them into the ground till planting time.
The most critical thing is to protect roots from drying out. Providing you are collecting trees suited to your climate zone its really not much maintenance trying to keep newly collected material safe as they have evolved to withstand your winters !!
if they were all dying from being dug up in winter and placed in cold sheds, there would be no bare root industry because they wouldnt be making any money.
yet some are still confused