What is the mechanism by which a tree, under stress, decides to redirect its nutrient flow from an apparently healthy part of the tree in order to produce new growth from dormant buds below and and to initiate complete dieback of the part now deprived of nutrients? It seems counter-intuitive for the tree to expend its resources to produce completely new growth as opposed to a partial dieback of the existing growth.
J--I have a couple telopea seedlings right now that are doing what you've mentioned. They "stalled" and actually lost most or all their old leaves, obviously I did something nasty to them, and have sat under my growlights for months doing absolutely nothing. Now new growth is popping from dormant buds lower down, rather than from the existing terminal buds...I continue to study these plants but I can't figure out why they would do things "the hard way"... At least I will wind up with some very nicely branched plants...but I really can't figure out this mechanism! Glen
Bacterial blights can cause a blockage in the arterial flow causing die back. Generally along the higher branches.
The tree in question was bare-rooted for its trip across the border after which it spent the next 10 weeks recuperating in a greenhouse. I then took custody and transplanted it to another pot. The tree responded well for 2-3 weeks, putting out a few flowers and a bit of new growth before loosing leaves at the rate of one a day. The leaves looked good at this point even though there were still signs of stress from the bare-rooting. The leaf drop increased with time and was followed up with branch dieback. However the tree managed to send out three new stems before the old growth suffered a complete dieback. Perhaps the repot was a further stress the tree could not handle. I can imagine something like this happening to a herbaceous plant, but a tree? Doesn't seem likely but obviously I am mistaken.
