There are a set of standards and specfications for nursery production of trees, believe or not they were written 11yrs ago!! Yes I know it takes time for change to happen but still 11yrs! Maybe the problem is that we as a profession don't know about these standards, or how to encourage the adoption of them by the nursery industry.
I recently did a plant stock inspection using the NATSPEC standards "Specifiying Trees" for a major company in Queensland, and so its been on my mind. I won't put the book up as
1) I don't have it as a pdf and to post it as scans would take too long and
2) the author deserves money for his work.
However there is a sample available on the net so I've posted that.
SpecTrees.pdf
It stems from the same work done in the US by Gilman et al and their work is amply explained and detailed here
http://hort.ifas.ufl.edu/woody/nursery_production.html
theres 15 links to follow there that explain why and how the standards were developed and implemented, note there is a federal standard ANSI Z60.1 but also state standards in Florida, and California.
So if its an area you have some involvement in ie advising landscape design etc get yourself a copy of the book, or just engage your larger nursery supplier in a discussion about standards in production. I would bet that like me you have all seen way too many problems and defects in trees as a result of poor stock right back at the nursery stage....it aint necessary, proper production practices remove those problems completely.