The leaves of this species are similar to those of the Chinese elm expect
they are tiny only 3 to 5 mm long.

What you probably have there is Ulmus parvifolia 'Hokkaido.' It is not a
hybrid; it is a very dwarf cultivar.

One variety has yellow margins and is sold as variegated.

There are two or three variegated cultivars of Chinese elm. You would have to
give us more information before we can determine which one. However, they all
get about the same care.

But when we transplant the rooted cuttings, most of them do not survive.
Same problem is encountered when its Bonsai is repotted.

Some of these cultivars are very fussy. If you want a dwarf Chinese elm that is
easier to care for, try to get hold of 'Seiju.' Meanwhile, leave your rooted
cuttings in the original bed longer before you transplant them, and try not to
disturb the roots of the cuttings or bonsai when transplanting. I gave up on
'Hokkaido' because it is just too much trouble, but I love my 'Seiju.' After
only a few years of training it looks like a real old tree.
Another dwarf elm that appears to be foolproof is Ulmus xhollandica 'Jacqueline
Hillier.' You will probably have to get both of these from US or Europe. I
don't know if they are available from China or Japan.

Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)