From all that I have read, I believe they are extremely resistant to dying from Dutch elm disease. While they can contract it, and spread it to elm trees they are very unlikely to die from the disease or be impacted by it. I live in Michigan and Dutch elm disease has killed off many or most of the Elms around here, but does all of the zelkovas have seemed to do well. I know that they do have issues depending on the variety you choose with temperature and are much more sensitive to clay soils and other things that do not seem to bother American elm trees so you would want to look into that nefore deciding on one. The other thing to look out for when buying a zelkova tree is that they do not have multiple leaders. I purchased one a few years back before I knew what a proper shape for that tree was, and ended up getting one that to my eyes looked pretty, but actually had a very poor branch structure. If you do end up picking one for your neighbor, be sure to consider the branching structure and pick a good specimen.

To reiterate, I would be more concerned with a dying from improper soil or the temperature verses contracting Dutch elm disease. Are there others nearby that are doing well?

I looked at Zelkova, but chose Chinese Elm (Allee variety) myself.

I had the same basic questions about DED, and when I researched it online, it was my understanding that a tree considered DED resistant was unlikely to die from DED, but could still be damaged by it.

I did some searching online just now and could not find a reference supporting what I just told you; I'm going on memory.

Richard.

P.S.: I wasn't too thrilled with the branching structure of Zelkova; it's a matter of taste, but you might want to check it out. My impression from reading was that it was like holding your arm up & spreading your fingers; that was the trunk plus branches effect, and while it's hard to describe what I mean, if you look at pictures you might can see it.