zelkova serrata

I am planning to develop a big zelkova serrata forest (tallest tree to be 50 cm or 20 inches at least) which will be something like the forest bonsai by Vaughn Bantingburch below. For that I bought 5 zelkova saplings at the first week of this May. I made a trench in the garden with a depth of...

This was sold as an Ulmus Parvifolia and then came with a sticker that said "Zelkova Parvifolia". I have read what I can find about their differences but still feel unsure. Most important is it to know if it's a Zelkova or an Ulmus, as I will be keeping it outdoors in Norway through the winter...