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Rootstock Crowding Study

I wanted to bring attention to a study we are doing at Walden Heights. In both research and direct observation, there is evidence that crowding of root systems leads to some dwarfing effects. Apples in particular tend to avoid growing in the same soil regions that other members of their species do. ( Atkinson D, Naylor D, Coldrick GA (1976) The effect of tree spacing on the apple root system. Hortic Res 16: 89-105 ). Additional consideration is that direct competition of many other species in the vicinity should lead to an overall size reduction. By creating a full block planting, roots will be forced to compete 360 degrees.

We have planted two sections to standard stock apple, one as an 8×8 foot grid, one as an 4×8 foot grid. We also, for comparison have standards at 15 x 15, and 30 x 30. We also have apples (part of another test) in a high tunnel at 8 foot spacing. Since we alot of scionwood collection for the nursery, if the fruit production is, well, unfruitful, there is still merit in the exercise. We are forced by necessity since we need to find room for what is closing in on 500 varieties, without resorting to dwarf stock or excessive topworking. It gives us an opportunity to run such a test without risking too much. We will keep everyone posted on the progress. There are about 500 trees in the two blocks, of 6 standard rootstocks and roughly 300 scion varieties.

Obviously precocity isn’t necessarily being addressed, at least at first glance. Since stress often leads to early bearing, who knows. If excessive pruning is needed in the early years, this may actually delay bearing. Our goals here have never been for rushing the crop- thats what berry bushes are for. Tree longevity and low maintenance plants are. If we can couple this with a tree that can more within reach for spraying, harvesting and scion collection, it may have a place in many a farm plan. Not as a replacement, but as an addition to the overall system.