Hi everyone, I started to probergate trees quite a few years ago and have never lost the new found bug..

I am finding it difficult to find legitimate information regarding the needs (environmental) for my Japanese Grey Bark Elms, 6 years old and have started there life in some harsh environments....... they spend only a few months outside (warm season) each year. I have recently move and now have a west facing garden (and this is perfect for so many other gardening options, but I am concerned... this week and possibly a little more we are going to experience -4 to -5 degrees Celcius.. I am going to bring my seed grown elms in and risk my toddlers lol, but do I really need to? (Still in training pots but deliberately oversized)

This site is very useful, see the link
www.bonsai4me.com/SpeciesGuide/Zelkova.html

Thank you, that was helpful, it seems my tree are still fit for outdoors as they have not become evergreen yet, I have allowed the cold to a point where the leaves fall each year. Now they have matured a fare bit I will leave them outside now.

Leave them out. It is far worse to keep moving them from a cold to a warm environment. They should never be inside other than a cold greenhouse or polytunnel.