Gee, 45' mulberry trees with 3' dia bases. Do they get all long and hang like that?
But have a read of this link toward the bottom, recommends root severence and branch bending to produce fruit.
http://www.abc.net.au/gardening/stories/s984425.htm
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Here's an extract from another site about how some trees require pruning for production
At one extreme are trees such as peach and nectarine that only bear fruit on stems that grew the previous season, so they need fairly severe annual pruning to stimulate a flush of vigorous new shoots for the next year's crop. Citrus trees only need minimal (Renewable) pruning as the more leaves that are on a citrus tree, the larger and more numerous the fruit. Trees such as Figs and grapes need a more specialised type of pruning.
http://www.daleysfruit.com.au/fruit%20pages/pruning.htm
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Cherries for example bare fruit on older wood, and need little pruning apart from the removal of dead or diseased wood - whereas peaches bare fruit on the previous years laterals and should be pruned to encourage new growth for the following years crop.
http://home.vtown.com.au/~dbellamy/fruit/apple1.html
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Mangoes flower on the growth from the previous season on the outside of the tree.
http://www.greengold.com.au/greengold/CARENOTES/CARENOTES/mango.htm
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Around these parts they pretty well cut wherever it suits them. But our fruit trees here are mango, pawpaw, avacado and clients often want these kept low for getting the fruit off. If you did target cuts and went to standard you'd have a darn big tree, I try to balance it a little, a few target cuts for structure and a few stubs preferably keeping cuts under say 4" dia ... it's a tough thing when you mainly look after amenity trees not fruit trees. I always ask the purpose of the pruning ... for fruit or for looks etc as some people don't care about trying to pick the fruit ... just let it fall off and rot! That's if the bats dont get it.
In commercial mango orchards they shear the canopy to keep it in check and get plenty of fruit.
But if I rocked up to an 80' veteran mango tree and they wanted it pruned for fruit production down to 20' high ... I'd walk as you have some massive ugly wounds on every branch, hideous. It's a tough balance when the trees are getting big, lot easier to keep a small tree small and productive.
Oh, I dont count banana's as a tree, you know how they harvest and prune those eh?