Zelkova is a genus of six species of deciduous trees in the elm family Ulmaceae, native to southern Europe, and southwest and eastern Asia. They vary in size from shrubs (Z. sicula) to large trees up to 35 m tall (Z. carpinifolia).
The name Zelkova ultimately derives from the native name of Z. carpinifolia in one or more of the languages of the Caucasus, as shown by the Georgian name, ძელქვა (dzelkva).
Like any genus, it depends on the species. Serrata and carpinafolia are the 2 most common in the US becuase they were brought in to fill in for the loss of Ulmus A.
The other 5 or 6 species don't get the clasic vase form so were not cultivated as extensivly.
Z. abelicia and sicula, for instance are a medium sized shruby montain species that are onle found on Crete and Sicily respectivly and are endangered. Though I've read of a few of them in Bot Garden collections.
Here's something I found on Z. serrata I keep on file for the halibut.
欅, ケヤキ
In the Japanese name, 木 means tree 挙げる means lift up hand, so a big tree that grows like a raised hand is the meaning of 欅.
I did some research on them as a substitue species a while back since a number of the hybrid elms were not looking good as they matured. I think it was homestead that suckers so much it needs regular pruning (wood should look cool though!)