Emerald Spire crabapple is produced by grafting onto Dolgo crabapple stock. I know that apples are commonly grafted onto crabapple rootstocks to dwarf them. On a Dolgo root stock the tree nominally gets to be 15 feet high x 6 feet wide.
Can you do the opposite: graft crabapple scion wood to a full size apple rootstock to get a larger tree? I would like to get a 30 foot high tree.
Dolgo is considered a semi-dwarfing stock. I believe grafting a crabapple tree onto a standard apple rootstock will produce a larger, but not full-sized tree. I haven't found any sources from people who have done it, but logically, evening out the characteristics (the smaller growth habit of the crab, and the bigger supply from the standard apple, which has the potential to give more energy than the crab can utilize, especially under ideal conditions), the tree will be sturdy, bigger, but not standard size.
Crabapples are usually more disease resistant and poor condition tolerant than standard apples, which is why standard apples are often grafted onto crab apple rootstocks. Reverse this, and I'd expect reversed performance as well, in these regards.
Also, standard apples are often healthy seedlings, but seedlings will be slightly variable in all respects, because of genetics. If you want to go higher quality, you can clone a disease resistant and vigorous tree for use as a rootstock, by mound layering. You basically cut the original stem down (coppice), and then when the new shoots are a suitable height, mound soil up around the, to promote new root growth. The process is summed up in the picture:
No it is not, or if so, not by much.
According to Jeffries Nurseries, Dolgo crab is used for their apple production, and the resulting trees are standard or very close to standard. This was private correspondence, and so I cannot provide a link.
http://www.artsnursery.com/article/Root-Stock-Reference-Guide
Indicates Dolgo is 30-40 feet high x 20-30 wide.
By itself, a large size does not require that it be non-dwarfing, but it's a good indicator.
Another article: https://sites.google.com/site/alaskafruittrees/rootstock
Malus Dolgo. (Dolgo Crabapple) I grafted some to this last year and I'll see how they fare over winter, before deciding whether to include it as a rootstock. It will produce a standard sized apple tree. This tree grows upright with an open habit around 30' in height with a 20-30' spread
