Dwarfing Interstocks: Their Effect on the Field Performance and Anchorage of Apple Trees

Abstract

SummaryAn interim report is given on an experiment in which trees of Cox’s Orange Pippin and Worcester Pearmain, 5 years old and incorporating dwarfing interstocks, are compared with single-worked trees using the same dwarfing clones as rootstocks. The dwarfing clones used as interstocks were M.VII, M.26, M.IX, M.VIII, M.XX and 3426 and the root systems were MM.104 and M.VII. The interstocks dwarfed the trees roughly in proportion to their dwarfing effect as rootstocks, giving a range of tree size down to about a fifth of that of control trees single-worked on MM. 104. There was a corresponding increase in precocity.In comparison with the controls, interstock trees were less firmly anchored, apparently because the rootstocks were dwarfed at least as much as the scions. Interstock trees were much more liable to develop root suckers than were single-worked trees of the same vigour.With the exception of M.IX, which was as dwarfing when used as an interstock as when used alone as a rootstock, the interstocks produced trees intermediate in vigour between that of the two rootstock components used separately. The ratios of crop to stem sectional area of both single-and double-worked trees conform to a single pattern of behaviour, suggesting that, in general, interstock trees are neither more nor less productive for their size than single-worked trees.