The pedigree is unknown and it was selected in England from a group of French genotypes known collectively as “Juane de Metz” in the late 1800s. M.9 is the most widely planted dwarf apple rootstock in the world and at least 30% of the trees in the U.S. are on M.9. M.9 EMLA is free of known viruses and is slightly more vigorous than the original M.9. Over the years European nurseries have selected clones
Because many dwarfing rootstocks have less than the desired level of cold resistance and trees on all dwarfing rootstocks require support, dwarf rootstocks are sometimes used as interstems to combine the desirable characteristics of a vigorous understock and the dwarfing interstem.
Interstem trees consist of three parts:
- A vigorous rootstock (usually MM.111 or MM.106)
- A dwarfing (usually M.9 or M.27) interstem is grafted to the rootstock. The interstem is usually about 6” long, but additional dwarfing can be obtained by
Espalier is a technique of pruning and training apples in two dimensions, usually against a flat surface such as a wall or fence. The rootstock that you choose needs to induce enough vigor in the scion cultivar so that growth occurs but does not produce a tree with too much vigor. The environment where you are located will alter this decision. The colder, northern areas of the United States — that is, USDA hardiness zones 3 and 4 (look up …