Experience from Florence, Italy - 3 years.
Make sure the tree experiences winter.
It should stay dormant for 2 months on a window with the cold coming through single pane glass.
It will grow indoor easily with 6 hours of sunlight for the Spring to early Winter ,
Florence is a zone 9. Snow after December 15 or so and until March / April.
This is for a 10 year old Zelkova grown from Seed.
As the Fridge goes. Vegetable crisper temperature is all you need.
You are allowed to bag the tree's top, just not wet, lightly moist.
However with Celtis [ Africana or Laevigata ] you cannot really stop the fine twig die back.
Which is why these Celtis work best as trees over 15" in size. The sewing needle fine branches die, but thicker
branchlets look normal.
The zelkova, never showed any die back with the Florence experience.
Good Day
Anthony