Malling 9 is the most popular apple rootstock in Poland, closely followed by M.26, but growers are also using dwarfing Polish rootstocks, and Geneva rootstocks are being tested.
Dr. Alojzy Czynczyk at the Research Institute of Pomology and Floriculture in Skierniewice, Poland, said the climatic conditions in Poland are variable, with extremely cold winters from time to time, particularly in the eastern part of the country. The growing season lasts about 200 days. Most of the country has light, sandy soils and relatively low rainfall of between 20 and 24 inches annually.
Czynczyk recommends that growers plant apple trees on dwarfing or semi-dwarfing rootstocks, depending on the soil, with between 1,000 to 3,000 trees per hectare (400 to 1,200 trees per acre). The most popular training system is the spindle bush.
In orchards planted in Poland between 2003 and 2007, 38 percent of the trees were on M.9 rootstocks, with 33 percent on M.26 and 9 percent on M.7. Seventeen percent of the trees were on the Polish rootstocks P.14, P.16, P.22, P.59, or P.60.
P.14 is a semidwarfing rootstock that is a little more vigorous than M.26. Young trees on P.14 need support and start bearing the second year after planting. Cropping efficiency is similar to M.26, but rooting in stool beds is better than with M.26. It is moderately winter hardy, and has low susceptibility to fireblight.
P.16 is weaker than M.9 but stronger than M.27. Trees on P.16 are productive and have a high cropping efficiency. Rooting in stool beds is similar to M.9. The rootstock has moderate susceptibility to fireblight.
P.60 results in a tree that is about 30 percent smaller than a tree on M.26. Trees on this rootstock are productive and the cropping efficiency is higher than with M.26. Trees must be staked. Fruit is generally large and well colored. Rooting in stool beds is good.
P.66 is a new rootstock from a cross of P.22 and M.26. Trees on P.66 are less vigorous than trees on M.9 EMLA. They are very productive with a higher cropping efficiency than M.26. Fruit is large. Rooting ability is better than with M.9. This rootstock is recommended for intensive orchards on good, irrigated soils. It is moderately susceptible to fireblight.
P.67 is more vigorous than M.9 EMLA. Trees on P.67 begin cropping in the second year after planting and are productive. Trees must be staked. Fruit size is good. This rootstock has low susceptibility to fireblight.
Czynczyk said that P.14 and P.60 are the most important semi-dwarfing rootstocks because they are suitable for the light soils that predominate in Poland.
Scientists at the research institute have also studied six new rootstocks from the Cornell-Geneva breeding program. Based on seven years of results, Czynczyk believes that G.11, G.41, CG.4013, and G.202 are the most promising for Poland’s conditions.