North American Fruit Explorers mailing list at ibiblio

[dwoodard@becon.org]

Several decades ago a study by a New Brunswick (Eastern Canada) 
researcher was published in the Journal of the American Society for 
Horticultural Science on the frameworking of apple trees. It was 
found that the productivity over time of apple trees growing in the 
commercial orchards in colder areas of New Brunswick was much greater 
and more regular when the fruiting cultivar was worked on a hardy 
framework such as Antonovka. The conclusion was that the framework 
did not affect the actual hardiness of the scion but made the 
recovery of damaged wood very much faster, when only the actual 
fruting parts of the tree were damaged and the trunk and inner limbs 
were undamaged.

However, as far as I recall the only leaves on these trees were those 
of the fruiting cultivars.

We do have several reports from NAFEXers of hardy branches with 
leaves on them increasing the coldhardiness of less hardy fruiting 
cultivars on which they were worked. However, it is important to 
remember that the coldhardiness of a tree increases steadily from the 
onset of dormancy to a peak sometime in January and then gradually 
declines. Near the peak of hardiness the curve of change with time is 
normally fairly flat.

I don't think that we have any idea yet of whether the reported 
beneficial effect of a hardy partial top on a less hardy remainder of 
a tree, is due to an increase of the resistence of the tender part to 
deepest cold, or to the tender part achieving its previous maximum 
hardiness (and no more) quicker and retaining it longer.  I suspect 
that we should be cautious and assume the latter for the time being. 

This question should be of some theoretical interest and although 
I suspect that not too many commercial growers would be interested in 
such a labour-intensive technique, it should be possible to interest 
some scientist in the question if we could canvass enough of them.
Does anyone have any bright ideas about researchers who might be 
interested?

I must admit that I have not been reading the scientific literature 
in the last 13 or so years and so my assertion that "we don't have 
any idea" may not be true of the scientists.

I definitely recall that the New Brunswick work showed that Macoun 
was a little less coldhardy that McIntosh. A rather vaguer memory 
suggests that Cortland was found to be a little hardier than McIntosh.

Douglas Woodard


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