Here are the basics in a perfect world:

The rootstock matches both vigor and climatic performance in your area to accomodate the scion.

All influencing the above: temperature, soil, understock availability (big one) and other "influential things" that aren't crossing my mind, well...disease resistance, etc -
Of course it would all be great if the understock and scion were of the same species (again perfect) but vigor still a possible reason.

Again it's like throwing the whole scientific book at a guy asking him to explain why some cultivars have different forms within the garden.

Sometimes cutting-grown conifers may exibit traits unlike a grafted plant of the same cultivar but these are very few exceptions and they are already known. I believe Picea glauca 'Echiniformis' is a plant that fits this category.

Then aside from science, who knows when "An Act of God" will occur.

Dax

Quantum Physics Anyone?? Abbot and Costello's, "Whos on First"??

and.. if container grown ... i would question how much fertilizer is in the pots .... and consider reversion to normal growth once planted into mother earth ... ken

Thanks for the feedback everyone. The plants i have seen have mostly been field grown, potted and generally grown on for about 6 months or simply done B+B style and there growth has all been similar however considering the source (who i won't libel publicly) i have to think it's possible they might just be growing some mis-identified Picea pungens clone. Can anyone point me to some good information sources on this topic be it journal or book form (i can hit the local university library's).
Thanks Mark

The Grower.

Dax