Answer: Pruning is a skill that is best explained with diagrams - it's safer for the trees, too! But I can tell you a bit about pruning plums. First of all, they're still fairly young, and will bear more as they grow older and have more fruiting spurs. Pruning in the early years of a plum tree's life should be focused on training it to the right kind of form for the species (Japanese plums require an open center, European, a central leader trunk, and there are variations in growth tendencies from variety to variety, etc.). What you are aiming for in pruning is strong, lateral branches that are well spaced for sun and air exposure and have a sturdy branch angle from the main trunk (between 50-80 degrees). I can recommend the Cornell University website where you can order a low-cost bulletin that covers cultural and pruning basics for plums and other fruit: http://www.cce.cornell.edu/publications/fruit.html
and I also suggest that you contact the supplier from whom you purchased your trees and see if they can offer you free info/diagrams for pruning - they should have provided those at the outset. Hope this helps!
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