affect of pruning on shrub or tree root spread
Yes, when you reduce the crown of the tree you reduce its ability to generate food. As a result, growth of the entire tree will be reduced. "Root impacts are proportional to the amount and strength of the growth control path destroyed. Topping or primary pathway disruption leads to tremendous root problems. Large amounts of active pathway pruning will constrain root growth. Marginal growth control path disruption probably has little effect on roots. " The more severe the pruning the greater the reduction. However, the more you prune the canopy, the more you compromise the overall health of the tree. Please see: http://warnell.forestry.uga.edu/service/library/index.php3?docID=146&docHistory%5B%5D=2
Thank you for the info. Do you recommend not doing the following even if annual pruning keeps the crown from growing beyond 5'?
Cut the top of the tree back to about 5 feet tall to maintain the compact size of the quince. If the tree is severely overgrown, you might have to reduce the height in stages, removing no more than one-third of the total length of individual branches each year until the desired height is achieved. Pasted from <http://homeguides.sfgate.com/trim-quince-54004.html>
I have also read: " The fruiting quince tree (Cydonia oblonga) performs best when pruned to an open-center shape, which allows air and light to penetrate the tree's canopy and ripen the quince. "
If you need to reduce the size on an overgrown quince (Cydonia oblonga), I would recommend you do it over a three year period, using selective pruning (not hedging or topping). This way you can reduce the height and open up the crown to light gradually. However, the common quince is a large tree growing 15-20' tall and it may be difficult to successfully reduce it's height so much if already mature.