the main growing branches of esp. fruit trees are called leaders -
better than calling it double leaders, as this sounds like the wrong kind of duality (!)

this is about another pear growing/training system in Australia:

The Tatura trellis also evolved with different ways of arranging and training trees on the trellis, to reduce the cost of establishing a Tatura-type orchard and make it more cost-effective. For instance, to overcome the high cost of nursery trees, we halved tree density in an open Tatura by training each tree with two leaders (called open Tatura with twin leaders), compared with one leader per tree (called open Tatura with single leader).


http://www.goodfruit.com/issues.php?article=668&issue=23

mat: PDF/Adobe Acrobat - View as HTML
such as lindens and Bradford pears, are densely branched. Good pruning ... Sometimes a tree will develop double leaders known as co-dominant stems. ...
www.lvsnag.org/pdf/PruningYoungTrees.pd

http://hgic.clemson.edu/factsheets/HGIC1351.htm



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Note added at 5 days (2007-02-27 20:53:55 GMT) Post-grading
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re Valerie's comment: espalier training is different and also quite traditional, whereas this is an innovative method (and "TMd" to boot!)