M-4 X Common Antonovka, bred by Dr. S. W. Zagaja at Skierniewice, Poland.
Influence on Scion Habit
P-18 produces trees that are B.118 to seedling size (or about 95% of seedling) and free standing.
P-18 is resistant to collar rot, apple scab, powdery mildew and crown gall. Susceptibility to fire blight is intermediate like that of M-4. P-18 produces well-feathered maiden trees with no burrknot tendencies.
P-18 roots very well by mound layering and produces few lateral branches. P-18 produces large calipered, well-branched maiden trees with good rooting and is well adapted to various soil types.
P-18 is very winter hardy, like Alnarp 2. This understock could be used on wet soils because of its horizontal rooting habit. P-18 crops in three to four years and could be used as an interstem base because of its adaptability to various soils and climatic conditions.