Tree Fruit Leader, Vol. 3(1) Jan. 1994

Little Trees, Big Yields

by Joe Fitzpatrick, Manager BCFG Test Orchard, Oliver, and
Mike Sanders, Tree Fruit Specialist BCMAFF, Kelowna

Because rootstocks have an important influence on productivity and size in fruit trees, the choice of rootstock is critical in the design of orchard plantings. This article summarizes the results to the end of the 1992 growing season of a trial started at the BCFG Test Orchard, Oliver, in 1986. The trial evaluates a range of rootstocks, from dwarfing to full-size, for growth and productivity.

The choice of rootstocks for the trial was based on practices current in 1986 and on anticipated use. The dwarfing rootstocks tested were M.9, B9, Mark, Ottawa 3 (O3), and M.26. The more vigorous ones tested were M.7a, M.2, M.4, Alnarp 2 (A2), and Antonovka seedling. Non-spur McIntosh and spur-type Red Delicious were the varieties used in the trial.

Trees were planted in soil which varied from sandy loam to loamy sand and were irrigated with solid-set sprinklers under the trees. Trees on dwarfing rootstocks were trained using a combination of slender spindle and central leader techniques. Central leader was used with the more vigorous rootstocks. The dwarfing rootstocks were supported by posts and the more vigorous types left unsupported.

Results are given as cumulative yield efficiency, calculated by dividing cumulative yield by tree size, that is, the dimension of a cross-section of the trunk.

Table 1. Cumulative Yield Efficiency and Tree Size

For both varieties, the results clearly show big differences in yield efficiency between the dwarfing rootstocks (B9, M.9, Mark, O3 and M.26) and the more vigorous ones. There are also yield efficiency differences within the group of dwarfing rootstocks; with McIntosh, B9 and M.9 have the highest yield efficiency followed by Mark and then by O3 and M.26. With Red Delicious, Mark and O3 have the highest yield efficiency followed by B9, M.9, and M.26. For both varieties Antonovka is the least efficient of the rootstocks tested. This was the most-planted rootstock in British Columbia up to and including 1980.

Differences in tree size are identical for both varieties except that with McIntosh, Antonovka produced the largest tree, followed by A2; with Red Delicious, A2 produced the largest tree, followed by Antonovka. It is interesting to note that with both varieties M.9 produced a smaller tree than B9. In other such trials the reverse has often been found. In any case, the differences are not great.

Dwarfing rootstocks are necessary to control tree size in high density plantings. This trial shows that these rootstocks not only control size, but result in a more productive tree than the more vigorous rootstocks.

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