The usual advice on water sprouts is you can cut them any time. Somewhat less common is "prune when the shears are sharp"- giving license to 4-season pruning. Simple advice, however, doesn't tell the whole story. There is the accepted truism that "all pruning is dwarfing" which is generally true but with a couple of exceptions (such as when you prune spur wood). Related to "all pruning is dwarfing" is the information that summer pruning is more dwarfing than winter pruning and that late spring pruning (before fully developed leaves have had time to harvest significant energy for the rest of the tree) is the most dwarfing of all. So on a young plum tree you can certainly mop out the water sprouts any time but you may be paying a certain price in the speed in which the tree fills out the desired space. I believe that water sprouts don't just feed themselves (like spurs) but also transport significant energy downstream to structural wood and roots.

Wait until they are actively growing, or else if you prune when dormant you risk getting water sprouts or other unwanted growth. I read this in the book "Backyard Orchardist" http://www.netwrite-publish.com/garden/prune-plum.htm Here is a link that might be useful: Pruning

This forum is very slow. You might want to try the Fruit and Orchard Forum. They will likely want to see pictures. tj

I'm sorry that I missed this! It's a busy time at work and in the gardens for me. I remembered some information that I had read on the Aggie Horticulture site. I don't have suitable growing conditions so have no fruit trees, so no real experience to speak from. Stone fruit like peaches and plums are typically pruned using an open center method If you google 'open center pruning' you will find YouTube videos and demos for this type of pruning. The following link may be helpful. http://aggie-horticulture.tamu.edu/archives/parsons/fruit/pruning.html Good luck and show us your work :-)