M.9 was selected at East Malling from a number of stocks of Juane de Metz, a rootstock with a very long history. The original M.9, of which a number of variant clones are now known to exist, was followed in 1962 by M.9a. Most of the M.9 clones and the M.9a clone were subsequently shown to be infected with latent virus and a replacement clone was prepared at East Malling by heat treatment and designated EMLA 9.
Influence on Scion Habit
EMLA 9 has a dwarfing influence on all scions worked on it. It induces cropping early in the life of the tree. Moreover, the fruit is larger and ripens earlier in the season, especially during the early years of the tree’s life. Trees on EMLA 9 show a wide degree of tolerance to soil conditions, withstanding heavy soils and wet conditions. It is not, however, suitable for dry light soils. M.9a is a weaker rootstock than M.9. EMLA 9, though virus-certified, is distinctly more vigorous than M.9. All 9’s rarely sucker, but their roots are brittle, and trees on these rootstocks require staking throughout their life.
EMLA 9 is resistant to collar rot (Phytophthora cactorum). It is susceptible to mildew in the nursery and a regular spray program is recommended.
EMLA 9 roots well under our controlled conditions. With our good quality rootstock, well-feathered maiden trees can be produced.
In spite of some difficulties in producing M.9’s in the nursery, they are very widely used and can be recommended as dwarfing stock for all soils, excepting light soils in low rainfall areas. They are useful for high density plantings and as temporary filler in plantings of trees on more vigorous rootstocks. Their ability to produce high quality fruit, in terms of better size and color, has led to their very widespread use in all apple growing areas of the world.