Please refer this to your Magnolia Maven - I have a 2 M. Magnolia x thomsoniana, and was wondering just how fast this puppy will grow - I understand the ultimate size is likely to be fairly big, but was wanting to plant it reasonably close (about 2.5 M.) to something else. And a quick question for the master of Acers - I note from Vertrees that the name A. palmatum 'Roseamarginatum' has been frequently misapplied, and that this tree may well be Kagiri Nashiki although the name has been misapplied (particularly in the States) to Higasayama. What are the chances locally sourced trees under this name will be one as opposed to the other - or does it depend on where they came from?
According to Arthur Lee Jacobsen (in North American Landscape Trees, 10 Speed Press, 1996, out of print), M. x thompsoniana (M. virginiana x M. tripetala) is "Rare in North America" and "Less hardy than either parent..." and "...a "shrubby, brittle, multistemmed small tree." So, my guess is that it would be slow. He lists record heights as: 40' tall (multistemmed) (Belgium) and 24' x 20' (Seattle). With respect to acers, most of the material available here originates in Oregon, where, I suspect, the name confusion arose. I'm sure I've seen both locally (as very small plants), but 'Kagiri Nashiki ' more commonly. Since the two cultivars are fairly distinct, you should be able to sort it out. Look for spectacular colour of the developing leaves contrasting with the bud scales ("two-toned popcorn") on 'Higasa Yama'.